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Western Historic Radio Museum

Rebuilding the R-390A Receivers

Brief History - Assessing your Receiver - Disassembly

The Main Frame - The RF Module - The IF Module

The AF Module - The Power Supply Module - The PTO

Front Panel Restoration - Alignment - Performance

Miscellaneous Info on Variants and Accessories,

Restoration logs for:
R-390A built from Spare Parts, (2)1967 EAC R-390A Receivers
Collins R-648/ARR-41, Collins R-389/URR Detailed Restoration Log
Recreations of Arvin R-725/URR, ASA R-390A,
Clark AB Black Anodized Panel R-390A, USMC OD Panel R-390A

by: Henry Rogers WA7YBS/WHRM

     PART 2 - Contractors List, Receiver Alignment, Expected Performance, R-390A Diversity Operation, Building a R-390A from Spare Parts, (2) 1967 EAC Rebuilds

      PART 3 - Recreations of Famous R-390A Variants: Arvin Industries R-725, ASA R390A, Clark AB Black Anodized Panel R-390A, USMC Olive Drab front panel R-390A

      PART 4 - R-389 Restoration WARNING! This write-up contains "Extreme ODC" detailed information and it's long, Rebuild-Dynamotor R-648/ARR-41, R-392 Info, Other R-390 Variants, Security Dial Cover, CV-979 Cabinet

1967 Arvin Industries R-725

The R-725 is a R-390A that was modified by Arvin Industries to use a special-build Series 500 IF module that was an updated R-390 IF module (no mechanical filters.) Additionally, the R-725 has a ferrous metal shield installed over the PTO and a "hum bucker" addition that allows the PTO and BFO tube heaters to run on DC voltage. For the full story go to Part 3 of this article under "Creating an Arvin Industries R-725 Receiver."

PART 2

Other R-390A Details

The Contractor Companies, Contract Numbers, Build-Years and Production Quantities for R-390 & R-390A Receivers

R-390

1951  -  Collins Radio Co.  -  contract 14214-PH-51 (contract 14214-PH-51 was also used for R-389, R-391 and a quantity of 1027 R-390A receivers) 

1952  -  Motorola Inc.  -  contract 26579-PH-52

R-390A

1954, 1955  - Collins Radio Co.  -  contracts 375-PH-54 or 08719-PH-55  (1027 R-390As built on 14214-PH-51 contract)  '54 - 310 receivers, '55 - 4982 receivers

1955, 1956, 1958  -  Motorola Inc.  -  contracts 63-PH-54, 14-PH-56, 14385-PH-58     '54 - 3427 receivers,  '56 - 4909 receivers,  '58 - 6537 receivers

1959, 1960  -  Stewart-Warner Corp.  -  contracts 42428-PC-59, 20139-PC-60-A1-51   '59 - 2120 receivers,   '60 - 4511 receivers

1960  -  Electronic Assistance Corp.  -  contract 23137-PC-60 (may have been for modules only)

1961  -  Capehart Corp.  -  contract 21582-PC-61    4237 receivers

1962  -  Amelco Corp.  -  contract 35064-PC-62     3982 receivers   (Amelco was owned by Teledyne)

1963  -  Teledyne Inc. or Imperial Electronics Inc. - contract 37856-PC-63  3976 receivers  (some data plates show Imperial, others show Teledyne, who owned Imperial) 

1963  -  Stewart-Warner Corp.  -  contract DA-36-039-SC-81547 (may have been for modules only)

1966  -  Communications Systems Inc.  -  contract FR-11-022-C-4-26418 (this is an order number and have been for modules only)

1967  -  Electronic Assistance Corp. - contract DAAB05-67-C0115 (some data plates have the order number FR-36-039-N-6-00189(E) shown instead of the contact number)  
                                                           10,717 receivers plus 151 consumer (rocket tag) receivers

1968  -  Dittmore-Freimuth/EAC - contract DAAB05-68-C-0040    215 receivers built by Electronic Assistance Corp. for Dittmore-Freimuth

1984  -  Fowler Industries - contract N 00024-84-C-2027    5 receivers

NOTES:  The first 1027 R-390A receivers built by Collins will have long data plates with 14214-PH-51 contract number. This contract was used for R-390, R391 and R-389 receivers also. Remaining Collins R-390A receivers have short data plates with either 375-PH-54 or 08719-PH-55 contract numbers.

Shortly after Teledyne Inc. was formed, in June 1960, they purchased Amelco Corp. (they had invested in Amelco's initial start-up.) Imperial Electronics was also an early purchase by Teledyne.

Electronic Assistance Corporation was owned by the same conglomerate that owned Hammarlund in the sixties. It's often reported that Hammarlund owned EAC but Hammarlund, at the time, was owned by Guianini Scientific Corp. and Hammarlund Mfg. was located in Mars Hill, NC. The Hammarlund connection to EAC is vague, at best.

There are a few other contractors that were involved in producing R-390A receivers and modules but those listed produced the greatest quantity of receivers with Electronic Assistance Corporation building the largest number of R-390A receivers on a single contract at 10,717 and Motorola building the largest total quantity of R-390A receivers, although requiring three different contracts, ultimately producing 14,873 receivers.

It's generally believed that a combined total of at least 55,343 R-390A receivers were built by the various contractors.

Receiver quantities from: www.navy-radio.com

"Blue Stripers"

The St. Julian receivers were left out in the weather with no protection whatsoever. The receivers that were in the middle of the vertical stacks generally faired best while the receivers at the top of the pile got all of the rain, snow, sun and dirt and the receivers lower in the pile got all of the debris "run off." The duration of the storage depended on when certain pallets were sold off. At one time, the receivers sold for as little as $37.50 per receiver, taking into account the entire pallet had to be purchased. Usually a pallet contained 12 receivers. Apparently, over the years, R-390As came and went at St. Julian's Creek Annex. Some receivers may have been sold in small lots but the majority were sold by the pallet. It appears that well into the 21st century, R-390A receivers were still being sold from St. Julian's Creek.

St. Julian's Creek Annex - piles of R-390As

It's difficult to tell how deep the pallets go (at least four deep) but they're all double-stacked

Another View of St. Julian's Creek Annex

12 receivers are strapped to each pallet. There are 216 receivers just in the front row of pallets and more behind that

The R-390A "Blue Striper" shown above was sold by Fair Radio Sales many years ago and, after its purchase, it sat for many more years in a garage in the San Francisco Bay Area. It was donated to WHRM in 2011 by NU6AM. Note that the panel was repainted a non-original very light grayish-white and the nomenclature has been filled in black. Additionally, this receiver has a Raytheon PTO dated 1977. I would think that this is probably a Raytheon rebuild of a Cosmos PTO. Overall, the condition of this "Blue Striper" is surprising good (well,...not that good.) Of course, none of the modules match (contractors) which seems to confirm that Fair Radio did "put together" this receiver from parts. What is odd is that Fair Radio would go through the trouble to assure that relatively good condition modules were provided and then use a "Blue Striper" front panel. Also, as expected, this "Blue Striper" is non-functional.

"Blue Striper Fate"

Update 2013: Unfortunately, like a lot of receivers in the condition that this "Blue Striper" is in, this one has become a source of parts to restore other R-390A receivers that have faired better. The RF deck has gone into a 1962 Teledyne R-390A. The IF module has a bad 4kc mechanical filter but may donate other parts to repair other IF modules. The PTO may go into the 1961 Capehart (but didn't, it ended up in the Imperial "built from parts" R-390A) The ON/OFF microswitch went to repair an Amelco R-390A. It's unfortunate but parts are what keep other R-390A receivers in "top condition" so they can be operated and appreciated for the impressive performance they can provide the user/owner.

Update 2022:  In 2022, I rebuilt a Capehart IF module and used the 8kc and 16kc mechanical filters and Z503 from the "Blue Striper" IF module (it's really a wreck now.) The "Blue Striper" front panel also was harvested for several mechanical parts for the Capehart OD panel rebuild in 2022. At the end of 2022, The "Blue Striper" made the final sacrifice by donating its entire Main Frame for the "R-390A Built from Parts" project. The only part now left is the front panel (minus all of its component parts.) "Parts sets" are a very important and an almost absolute necessity when restoring incomplete or challenged R-390As. 

R-390A Receiver Alignment - Miscellaneous Info

Things to do Before Proceeding to the Fixed-IF, Variable-IF and RF Alignments - you should first do your PTO end-point error correction, if necessary (it will be.) Be sure that the Calibration Oscillator is set correctly and the Veeder-Root counter is in sync with the PTO (you should have checked both before doing the EPE adjustment.) Also, check the Crystal Oscillator output at E-210 and be sure the voltage there is between -3.5vdc and -8.0vdc on the 8mc to 31mc tuning ranges. The voltage should appear when the MEGACYCLE knob is on its detent for each band and remember that the receiver must be in Stand By for this test. You don't have to check the .5mc to 7mc bands because these crystals and associated oscillator circuits are both fundamentally and harmonically operated and also work in either a double or triple conversion scheme. They were actually checked in the higher ranges. Be sure your DIAL ZERO is mechanically centered within its approximately one-sixth turn of the KILOCYCLE tuning when calibrated to any XX.000 (or any 100kc marker) on the Veeder-Root counter.

Error in Army TM 11-5820-358-35 and more - Field Depot and Maintenance Manual for the R-390A from December 1961. Alignment instructions, page 116, paragraph 76b (2) indicates that URM-25 Signal Generator should be tuned to 18.75mc. Actually, the correct frequency is 18.25mc. This error was very obvious to technicians doing the alignment and is very well known. Interestingly, the earlier TM 11-856A Technical Manual for the R-390A has the correct 18.25mc information, so this later error was probably a typo that wasn't caught in proof-reading. There are many conflicts in the Army TM schematics due to the reluctance of the Army to change the schematic. Instead "NOTE" is placed on the schematic that should guide you to a list of upgrades that changed the schematic or component value. Just be aware that if you're troubleshooting to the component level to double-check if a circuit value is in conflict with what is shown on the schematic.

How to do the Balanced Input Alignment - Make up a test resistance that consists of two 68 ohm 1/2 watt carbon resistors in series. Each separate leg of the resistors will push into to each terminal of the Balanced Input Twin-ax connector. The junction of the resistors will be connected to the signal generator. When performing the alignment of the RF stages first adjust the Balance trimmer on the the RF transformer for the minimum voltage on the DIODE LOAD as read on an (analog) VTVM. The Balance adjustment will not reduce the DIODE LOAD voltage to zero - you're setting the Balance trimmer for the minimum voltage. Be sure the ANT TRIM is set to 0. With the minimum voltage set, now proceed with the RF adjustments for that section of the receiver. Recheck the Balance trimmer adjustment after the particular RF section has been aligned. The Balance should still be close but will probably need just a slight adjustment for minimum voltage at the DIODE LOAD. Recheck the RF alignments - but there should be no significant change and just a slight "tweak" should be all that's required.

Stagger Tune the IF or Peak Adjustment of the IF? - Stagger tuning will give the IF bandwidth the maximum flat top possible with the mechanical filter selected. Early receivers were "peak" tuned for maximum response and may give a frequency bandwidth somewhat less than the mechanical filter bandwidth. Stagger tuning was used on the later IF modules and does give a better response in the receiver that is generally flat out to the limits of the mechanical filter's bandwidth. You can align early IF modules using the Stagger Tune method. Be sure to check the IF transformers to verify that the Q-spoiler resistors are present. Some IF transformers were modified by clipping out the Q-spoilers to have more IF gain but this also narrows the bandwidth. The Q-spoilers should be installed and connected for the best bandwidth. Updates to TM11-856A have the later procedure for stagger-tuned IF alignment, as does TM11-5820-358-35, or it can also be accessed from many sources on the Internet.

IF Cans without the Alignment Hole - Early production IF modules will have shields over the IF transformers that don't have a hole for alignment. This was to assure that the receiver's IF alignment wasn't tampered with in the field. When the receiver went back for repair or alignment the technicians had a set of covers with holes that were installed for the alignment and when the alignment was finished then the "non-hole" originals were re-installed. If you can't locate an extra set of IF cans then it will be necessary to drill an access hole for alignment. All later IF shields had the hole anyway and many early ones are found nowadays with the hole already drilled since the TM directs the technician to drill a hole for alignment purposes.

Slug and Trimmer Adjustments - One caution on adjusting the slugs and trimmers for the RF alignment. First set the Veeder-Root counter on the R-390A to the specified frequency. Then set the RF Signal Generator to its specified frequency. You'll notice that by "rocking" the Signal Generator frequency that there is a "peak" output on the Diode Load that is very slightly different from the Veeder-Root counter setting. Be sure to use the "peak" Diode Load voltage set by the Signal Generator frequency adjustment. Once you've set the signal generator to have the peak Diode Load voltage, then adjust the proper slugs or trimmers for further maximizing of the Diode Load voltage. Remember, the slug adjustments don't affect the receiver's frequency readout accuracy. That's a function of the PTO accuracy and the Crystal Oscillator. Always set for the "peak" response by "rocking" the RF Signal Generator and then adjust that band's slugs and trimmers for maximum output on the Diode Load.

Make up an adjustable trimmer that has a range of about 80pf up to around 130pf. Remove the cover from the mechanical filters on top of the IF module and then remove the 110pf fixed capacitor on the particular mechanical filter. Now "tack solder" the trimmer in its place. Power-up the receiver and select the bandwidth for the particular mechanical filter and adjust the trimmer for maximum reading on the CARRIER LEVEL meter. Remove the trimmer and measure the capacitance with a digital capacitance meter. Install a silver mica capacitor of that value to the mechanical filter. This may be enough to get the mechanical filter tuned enough for equal response but it usually isn't.   >>>

NOTE: Most handheld digital capacitance meters aren't even close for accuracy when measuring pico-farads. Not to mention that, at the pf scale, the test meter leads will also add significant C (some meters have a zero adjust but still the accuracy is limited.) It makes this sort of fixed-value tuning extremely difficult to do accurately. Unless the input/output fixed C is way off, it's probably better to just leave the MF tuning "as-is." The spec was within 5db of the other MFs. It would have to be over 10db before I'd try this method of retuning the MF. And,...actually an easier approach is to install the MWO for adjustable trimmers - well, actually just use an IF deck that already has the MWO, then just test and install. Keep the original IF module around just in case for some reason you want an "all original modules" R-390A.

Expected Performance

Here's what I like about the R-390A,...

1. If you absolutely must know exactly where in the electromagnetic spectrum you are listening, the R-390A and its family are the most frequency-accurate readout available in vacuum tube receivers. It's easy to achieve 1/2 kc accuracy or better. The mechanical-digital readout eliminates the vague interpretations of reading analog dials.

2. If you think you're going to be bothered by QRM, remember the R-390A was designed to intercept radio signals from the USSR, China, Cuba, East Germany and other Communist countries and to be able to successfully copy those signals through any kind of interference whether natural or man-made. The R-390A also provided reliable communications, including mobile RTTY, despite jamming efforts from some of our Cold War adversaries. The receiver can cope with just about any type of amateur interference since it was designed to work through "professional-level" QRM.

3. When the R-390A is rebuilt and correctly aligned it is very competitive as far as sensitivity is concerned. Are there more sensitive receivers? Of course. But sensitivity isn't all that's required to successfully copy weak signals. Nowadays, the ability of a receiver to function well in a noisy EMI environment is far more important than an "under a microvolt sensitivity" spec. After all, when your local EMI noise floor is a constant S9, what good is .25uv sensitivity? When all the available controls are taken into account along with the mechanical filter selectivity (and the user is very familiar with the operation and capabilities of the receiver) the R-390A is almost unbeatable as a station receiver.

4. Stability is the best in vacuum tube designs. Drift is non-existent.

5. You have two individual audio outputs on an R-390A. The LOCAL AUDIO is normally used to drive a 600Z ohm speaker set-up but you can also use the LINE AUDIO for the same thing - simultaneously! The LINE AUDIO was normally used to drive data devices like RTTY TUs, etc., but there's no reason it can't drive any 600Z load - like another speaker. I've set up a speaker in one room run by the LINE AUDIO and a second speaker in another room run by the LOCAL AUDIO. Independent audio levels in separate rooms. Really neat.   OR,...if you just want to utilize the LINE LEVEL meter to show a response to the audio component of the signal then install a 680 ohm 1/2W resistor across the LINE AUDIO terminals. You can now turn on the LINE GAIN and select the LINE METER scaling and the LINE METER will respond to the audio component of the received signal.

6. Everything about the R-390A's construction is "heavy-duty" and its use metal knobs imparts a massive "feel" to the receiver's operation. The R-390A has a certain impressive presence that attracts the attention of ham shack visitors. This seems to be true whether the visitor is familiar with the R-390A receivers or not. 

1. On SSB and the Meters - Although there were a couple of military SSB adaptors , the CV-591A (aka MSR-1 or MSR-4) and the CV-157, available and several modifications have been published and other add-on devices available for demodulating SSB produced, none of these are necessary for receiving undistorted SSB signals. Unfortunately, many new R-390A owners have only used modern equipment (with SSB Product Detectors) before going to the R-390A which only has a simple Envelope Detector. They expect the R-390A to be adjusted for SSB reception just like their modern receiver - RF GAIN at maximum with the AVC (AGC on the R-390A) on and volume level set by the AF GAIN (LOCAL GAIN on the R-390A.) The R-390A can't be operated like that when receiving CW or SSB. Before product detectors came along it was standard procedure when receiving CW or SSB to reduce the RF GAIN and advance the LOCAL GAIN (AF GAIN) so that the proper ratio of incoming signal to BFO injection could properly demodulate either CW or SSB. AGC was usually turned off but it depended on the receiver design. With the R-390A, AGC can be left ON to limit the maximum response, if desired. If the R-390A's BFO is properly set-up, its position allows selecting either upper or lower sideband. Now, you do lose the function of the CARRIER LEVEL meter (and most AGC action) in this method of reception but who cares? The CARRIER LEVEL meter measures DB over 1uV and its accuracy depends on the RF GAIN setting. If you were planning to use the CARRIER LEVEL meter for CW or SSB signal reports, most stations wouldn't even know what you're talking about when your report was so many "db over 1uV." It's all a relative measurement anyway, dependent on the frequency and conditions. It's better to operate the R-390A as a standard pre-product detector receiver for CW and SSB and just give your contacts an estimated R-S-T report.

2. More on the subject of SSB reception and Modifications - The CV-591A family of SSB adapters were built by The Technical Materiel Corporation. These adapters work from the IF output, therefore you lose the Noise Limiter function, the 800 cycle filter function and the dual audio section of the R-390A receiver if you utilize only the audio output section of the CV-591A. Now, if you happen to have an extra speaker, you can connect one to the CV-591A output (8.0Z or 600Z) and the other one to the R-390A's LOCAL AUDIO (600Z only.) If you want to do SSB or CW you can use the CV-591A and its speaker. If you want to do AM, then use the R-390A's LOCAL AUDIO and speaker. The CV-591 will provide excellent, distortion-free SSB reproduction and they are well-worth using. The only disadvantage is the price that the CV-591A is fetching today, sometimes selling for more than the R-390A receiver. 

On modifications to enhance SSB reception,...most of the mods that have been published do not improve the receiver's overall performance. Most modifications on any piece of vintage radio equipment will enhance performance for one area at the expense of overall performance. Besides, modifying a vintage receiver to make it operate like a "modern" piece of equipment seems to go against the whole idea of collecting, restoring, operating and preserving these classics in the first place. You're better off to learn how to use the R-390A properly and when you do, you'll find that modifications are not necessary for great performance in all conditions and in all modes.

3. On Audio Quality - Audio reproduction is not as bad as a lot of "BC-Quality AMers" complain it is. The mechanical filters provide a specific, very steep-sided bandwidth but some AM op-listeners are used to the "bell curve" that many early vacuum tube receivers had with only two fairly broad-tuned IF amplifiers. "Ringing" or a "hollow sound" were the usual complaints about the mechanical filter bandwidth. If you change the LOCAL AUDIO coupling capacitors to .022uf and then use a high quality 600Z transformer with a large speaker in a good enclosure, the audio sounds very nice, especially in the 8KC bandwidth (which is really close to 11KC) on AM with marginal signals or 16KC with a really great signal level (AM or SW Broadcast but it's hard to find quality program material being broadcast.) You'll have to do the same thing to the LINE AUDIO if you want to run dual audio lines to two separate speakers. However, if you're really into high-fidelity, then you can take the signal from the DIODE LOAD and run it through a shielded cable to a high-fidelity audio amplifier that's connected to a large hi-fi type speaker system. At 16kc bandwidth, AM signals will sound incredible. As with the SSB adapters though, you'll lose the NOISE LIMITER and 800 cycle audio filter functions with this "hook-up" unless you provide a separate speaker on the LOCAL AUDIO line (just in case you want to do CW.) For most users though, especially if you're using typical communications loudspeakers, the stock audio sounds pretty good and the original .01uf coupling caps are fine. I've only substituted the .022uf on a couple of R-390A receivers (and that was done years ago) and it's difficult to tell the difference between those receivers and the ones with stock coupling caps.

Break In Operation - The R-390A "Break In" function requires using a T-R relay with Normally Open (NO) contacts that change to Normally Closed (NC) when in transmit. This function operates the R-390A Break In relay and the R-390A Antenna Relays. The Break In function of the R-390A is opposite that of a typical receiver Stand By function that will require the T-R relay to provide a NC state for receive and NO for transmit. Most T-R relays, like the Dow-Key type, will usually provide a set of DPDT auxiliary contacts that allow connecting the R-390A Break In to one of the NO set of contacts. Most vintage military transmitters will have internal T-R relays that provide receiver antenna switching and also NO and NC contacts on the sending relay to control the receiver standby. Use of the Break In function is essential to protecting the R-390A's input circuitry. The Break In function totally isolates the receiver's input using relays to disconnect the antenna line and ground the receiver input. If the Break In isn't used and there's a failure within the T-R relay, full transmitter power might be fed directly into the receiver input. This failure mode is more common than one would think and shows up as a burned primary coil on (most commonly) the 2-4mc ANT/RF transformer (since most ham-use of R-390As is on 75M.) If there are no auxiliary contacts available for proper operation of the Break In, one can jump the Break In terminal on the back panel to ground. Then use the Break In switch (ON-OFF) on the front panel for the Stand By function. The same sort of isolation does happen when the Function switch is used for Stand By but using the Break In is the proper method for placing the R-390A in "stand by" during transmit.

The Weight Issue - No doubt, the R-390A is a heavy receiver weighing in at close to 85 lbs. Here's a hint for when you have to move the receiver. Remove the Power Supply module and the AF module. These two modules will reduce the weight by close to 20 lbs. With the covers off and the two modules out, the receiver weighs about 65 lbs - much easier to move. Of course, you still have to get the receiver to the work bench to remove the covers and modules (use a roll-cart.) This hint is really for moving the receiver longer distances, like to another room, ESPECIALLY when the moving involves going up or down stairs.

Cabinets - If you want the R-390A to be mounted in a cabinet you have two choices. First, is to find the proper CY-979 (or CY-979A) aluminum cabinet. This is a high-quality, military cabinet that is designed for the R-390-family of receivers. They are expensive. Originals were built from the early fifties up well-into the sixties. In the 1990s, an ad in Electric Radio offered CY-979 cabinets for about $150-$200. These cabinets were restored by W5MC and ink-stamped on the interior with an ID. There is some confusion on these restored cabinets as it wasn't clear in the ad if these cabinets were rebuilt old ones or new recreations. It doesn't seem likely that someone could have built a CY-979A complete with shocks and skids and then sell it for so little. But, since any original contractor ID was removed in the restoration process, the only ID is the ink-stamp inside which usually has a date with it (from the 1990s.) I've only seen one of these W5MC CV-979A cabinets and it was exactly like the original, with the screens inside the louvers, proper shocks and skids, etc. I would have to conclude that these W5MC cabinets are "restored" originals. If you are going for the CY-979 cabinet and you're willing to pay a high price be sure that the one you decide on has the shock mounts and the skids. It's fairly common to find CY-979 cabinets with the shocks and skids removed. These modified cabinets are incomplete and should be priced accordingly. For more details on the differences between the CY-979 and the CY-979A, go to the section on these cabinets at the bottom of the page in Part 4 of this write-up. Other than the CY-979, any other cabinet that is for 10.5" by 19" panels with a depth of 15" will also work. Several sources sell a new Hammond cabinet of this size. Although advertised as a "R-390A Cabinet" it really is just a cabinet in which the R-390A will fit. Price is several times less expensive than the CY-979.

Put on the CAL and the BFO, set the KC to xx.500 kc and rotate the MC change thru all bands to hear if the CAL oscillator is received on all bands. Turn off the BFO, make sure the RF Gain is fully advanced, AGC is selected and then, watching how much the CAL oscillator shows on the Carrier Level meter, run thru the bands again. The meter level should read over 40db. 50db is more likely if everything is aligned. Be sure to check all bands for CAL Carrier Level. With the CAL still on, check the EPE on any band. You should switch the Bandwidth down to 1kc for better accuracy. Be sure to also check the linearity every 10kc. That's an easy test that shows a lot. Recent alignment should have no more than 0.5kc EPE and an unknown PTO might have up to 4kc EPE but should still be linear with just a slight change each 10kc increment. These two tests are easy to perform and tell you a lot of info. If both tests look good, the receiver is probably in good shape. This applies to any R-390A that you want to perform a "quick check" to.

Since the CAL oscillator is practically connected to the Antenna Input, it serves as a onboard signal generator. If you hear the CAL oscillator when tuning through the 100kc markers on all bands (if you have a speaker connected,) then most of the receiver is working well enough to receive a strong signal. The reading on the Carrier Level meter will show generally how sensitive and in alignment the receiver is. Most rebuilt and aligned R-390As will show 50db+ on the meter at around 10mc. Check around 5mc and the meter should read the same or slightly higher. Check around 15mc and the meter will probably read less but still be around 40db. The EPE check just tells you if the receiver has been recently aligned by someone who is thorough and did do the EPE adjustment. EPE < 1kc, recent alignment. EPE > 4kc, typical of "as found" PTO.

You never know how a seller is going to react to this testing, so before doing any testing, be sure to describe what you want to do, what you're going to be looking for and why. Most honest sellers would welcome more detailed information on what they're selling. However, many sellers will react to this testing as a "haggling method" and become suspicious of your motives. If the seller has technical ability, they'll usually understand the testing and the results. If the seller doesn't even know what the R-390A is other than something to sell,...well, not much can be done in that situation. Actually, when dealing with non-technoid sellers, you're trying to access the condition of the R-390A for your own motives and from that information judge if it's priced accordingly. If it's priced fairly for its condition, then buy it. If it's not fairly priced,....well, all of the haggling efforts are usually a waste of time when dealing with the non-technical type of seller.

Dual Space Diversity Operation with the R-390A Receivers

With either method of Dual Diversity reception, the receiver set-up is the same. You will be connecting the DIODE LOAD from each receiver together. The receiver that you plan on operating as the "master" will have to have the DIODE LOAD terminals jumped while the "slave" receiver doesn't have the terminals jumped. The "slave" receiver is only operating to the detector stage and its audio output is not used. You can connect 500 ohm resistors across the LINE AUDIO and the LOCAL AUDIO on the "slave" receiver. You will also have to install the jumps to connect AGC DIV terminals together on each receiver. You will also have a wire connecting the AGC DIV from each receiver together. A speaker on the LOCAL AUDIO is only required on the "master" receiver.  To listen to just the "slave" receiver, turn the RF GAIN on the "master" receiver to 0 and what you hear thru its speaker is the "slave" receiver. Also, if you want to listen to just the "master" receiver, turn the "slave" receiver's RF GAIN to 0 and what you hear thru the speaker is the "master" receiver only. With both receivers operating and connected to their respective antennas, tune in a strong shortwave broadcast signal. Have both receivers' RF GAIN set to about 8. Don't set the RF GAIN on either receiver to "full on" (10) or each receiver will "fight" the other one for control of the AGC line. By alternately reducing the RF GAIN of each receiver to 0 you should be able to end up with both receivers tuned exactly to the signal. Once the SW BC signal is tuned in on each receiver you will need to "balance" the RF GAINs. Slowly increase the RF GAIN on the each receiver alternately to the point where you see the CARRIER LEVEL meter showing some response. Adjust the RF GAIN on each receiver until you have the highest CARRIER LEVEL readings on each receiver without one receiver or the other "overloading" the AGC line. When "overloading" occurs the CARRIER LEVEL meter on one receiver will drop much lower in its reading and with a reduction in the RF GAIN of the other receiver you'll see the meter reading jump back up. By "balancing the receivers" you get the best diversity response and the best sensitivity. You will note that the two receiver's CARRIER LEVEL meters will react differently since each receiver is responding to a phase difference in the radio wave based on the separation of the antennas. You should see deep fades that cause one CL meter dip while the other receiver's meter remains steady. You should also see a reduction in phase distortion if you are using the polar diversity set up.

Remember, you can only use AM reception on this type of Dual Diversity. That's because CW or SSB reception requires the BFO to be in operation and the BFO dominates the detectors and spoils the diversity effect. For RTTY reception special TUs were used like the CV-116 that was designed for diversity RTTY. Diversity CW reception required Tone Keyers.

So, give Dual Diversity reception a try if you can. It's interesting and sometimes beneficial to copy. 

 
photo above: A Dual Diversity set-up with the 1956 Motorola on the bottom and the 1955 Collins on top. Both receivers are fully rebuilt (including recapping) and both are fully aligned. Though the speaker looks like a Hallicrafters PM-23, it isn't. It's a homemade wooden cabinet that houses an 8" Jensen speaker and the louvers are made of aluminum. The cabinet is painted gray wrinkle finish.

R-390A Receivers and Variations
Rebuilding, Refurbishing and Recreating Projects

New for 2022                                                     Building a R-390A from Spare Parts   (2022)  

I'm starting the Rebuilding write-ups with this latest 2022 "parts set" project because it really doesn't involve a specific contract receiver. Rather, it shows the steps necessary to transform a collection of parts to a nice-looking, functional receiver. For many R-390A rebuilders, this is standard operating procedure since the majority of reasonably priced receivers will have gone though depot repair many times during their military service and no longer have any of their original modules. The object of this "Frankensteinesque Creation" (well, it is put together from parts scavenged from the boneyard of derelict non-operating receivers) is to illustrate that any of the modules and any of the parts are interchangeable by design and, regardless of contractor, any operational (and aligned, if necessary,) module can be used as a replacement in any working and aligned receiver and that receiver will function to specification. This project relied heavily on my collection of R-390A spare modules and "parts sets" along with many boxes of used hardware - the so called "junk boxes" that I've been gathering over the years,...decades actually.

Nov 27, 2022 - I got the Imperial R-390A down from the top shelf in the storage area. It's missing all of the modules except for the RF module. All front panel controls are present along with their correct knobs. Both tuning knobs are present. The Veeder-Root counter looks good and the dial cover is in pretty good shape. The Main Frame is a little "beat up" with some minor bends that should be easy to straighten. Back panel looks complete. All harnesses look good with the proper connectors (not exactly. I sure didn't look very closely at this Main Frame at this time.)

The front panel has a "fat finger" ring around the Kilocycle knob, BUT, I have an excellent condition front panel that is going to be used for this project.

Since Imperial Electronics was owned by Teledyne and Teledyne also owned Amelco, I think it will be acceptable to use Amelco modules in this Imperial R-390A. I've found the Amelco IF module - it wasn't with the other parts-modules but was upstairs in a back storage room. It looks in very good shape. I selected the best of the two Amelco Power Supply modules I had. I've also pulled an Amelco AF module that has "GOOD" written on the side but is missing the "plug-in" filter caps. I'm going to check the Raytheon labeled PTO that was installed in the "Blue Striper" and if it doesn't work out, I'll use one of the nicer Cosmos PTOs.

There are a few little things missing that can be scavenged from the other parts sets, like the dial lock mechanism and the dual crystal that plugs into the RF module. Almost all of the tubes were pulled sometime in the past, so I had to order two 26Z5 tubes. The remaining tube types I have in stock.

Although the Imperial R-390A looked promising up on the top shelf a closer look when it was on the bench revealed significant damage.
 

The Main Frame harness to the IF module had been "chopped" (probably to get the Amphenol connector.) Also, some of the coax cables were "chopped." That pretty much ruins the Main Frame except as a "parts source." Photo to the left shows the Imperial's problems. One more issue is the RF module is actually a Collins RF module with Motorola Crystal Oscillator module. I don't even know if this receiver has anything "Imperial" about it except the data plate. I'm checking two other RF modules I have since this Collins/Motorola is literally "loaded" with Lubriplate grease. It's everywhere. What a mess.

The Ax Attack -  I have a pretty nice looking EAC RF module that might work,...further close inspection is required because someone hit the side of the Main Frame that the RF module was mounted in with an ax. I'll have to see if the "ax attack" damaged the RF module beyond repair*. The EAC RF Module should have all of the late-version RF/Vari-IF transformers that usually don't have stuck trimmer rotors (Early version modules always seem to have stuck trimmer rotors in their RF transformers which is another reason I'm trying to avoid using the Collins RF module.)

The RF module is the most complex of the modules and it is the "heart" of the R-390A, so it does require a lot of attention to details to make sure it operates correctly.

photo left: Look at the Lubriplate grease slathered everywhere. No wonder the KC and MC tuning shafts won't turn. Lubriplate should not be used,...ever. It hardens quickly to become like cement (it was designed for rifle sliding action pieces that were cleaned and relubed often.) Also note, the cut harness and coax for the IF module. Lots of good RF module parts though.

The "ax attack" on this R-390A "parts set" (along with destroying all switches, cutting all harnesses and cutting the coax cables) was probably the result of deposition rules from some other bureaucracy that stipulated that the gear would become scrap and couldn't be usable or made operational - at least it wasn't taken to the dump and "bulldozed." Luckily, even though considered "destroyed" it has been a very good "parts set."

Next, I noticed that the Crystal Oscillator index wheel wasn't rotating as the MC was changed. The gear-to-shaft clamp was tight but the shaft slipped inside the clamped gear. I lubricated the shaft bearing and cleaned the two band switches. I used the slot at the rear of the switch shaft to rotate the shaft and felt binding with a grinding noise. I removed the entire Crystal Oscillator module (three screws) and then, when rotating the shaft, there wasn't any binding and operation was entirely smooth and light. The problem seemed to be the adapter bushing might be binding in the oil-lite bearing. Tried slightly changing the mounting position which helped a little. It feels like the mesh between the C-O shaft gear and the MC-drive gear was way too tight. There's no adjustment except to change the mounting position of the C-O module or to change the C-O shaft gear to see if that helps. I changed the shaft gear which slightly helped but still there was enough binding that the gear would slip on the shaft accompanied with grinding noises. I checked the gear plate to see if it was bent but it appears perfectly straight. It might be possible that the chassis of the C-O is slightly bent causing the misalignment - after all, the right side of the R-390A that this RF module was pulled from was hit with an ax. Replacement with another C-O should be revealing.

EAC RF Module and Gearbox came through the "ax attack" with only a few minor problems

The slug rack for the 2-4mc RF transformers was missing. I salvaged one from the "parts" RF module. The 2-4mc ANT-RF transformer was also missing. I salvaged a Teledyne transformer from the "parts bag" of RF/Vari-IF transformers. Inside, the band switch looks to be in good shape. It has fiberglass switch wafers and the capacitors are either ceramic disks or polyfilm types, which is typical of the late-versions of the RF module. Further checking and the slug rack springs were missing on the 8-16mc rack. Installed spare springs from the parts. I guess the ax-wielder tweaked the right rear panel of the slug rack guide and that was jamming the .5-1mc rack. Using a long 1/4" thick piece of metal for a lever, I bent the slug rack panel guide slightly "more open" to get the proper clearance for the .5-1mc rack to slide freely.

RF Module Gearbox Flush & Brush - I've been doing all of this examination and rotating with the gears and bearings dry. Since nothing is binding, I don't think there are any real issues with the gearbox. I usually do a WD-40 "flush and brush" to thoroughly clean and work some lubrication into the bearings. The WD-40 is mainly used as a solvent so the bushings will have a drop or two of machine oil applied following the clean-up. The gears themselves shouldn't be greased. The slug rack roller bearings need to be cleaned and lubed. The slug rack channel guides shouldn't be lubricated. Same for the cam surfaces. If the cams were greased, then the rack roller bearings would just slide in the grease instead of rotating like they should.

Dec 2, 2022 - This EAC gearbox was pretty clean already. Didn't take too much WD-40 to have the gearbox looking and feeling like new. I usually leave an RF module out in the shop for a day to "dry out" from the "flush and brush" (sets on the concrete floor with a large rag under to absorb the WD-40.) Further clean-up and mechanical adjustments will be necessary before this RF module will be ready for electrical check-out. Usually, when building up a R-390A "from parts," the most time is spent on the RF module because it has the most mechanical operations that must be synchronized and work together smoothly and accurately. While the RF gearbox was draining, I continued on with the Main Frame.

While I'm exchanging bed plates, I also have to remove the old "Blue Striper" front panel, so all of the knobs and controls have to be dismounted. Missing from this front panel are both meters (but I have replacements) and the dial lamp bezel with the #328 lamp sockets (also have several replacements.) The AC power micro-switch was missing but I have replacements. Everything else seems to be present but very, very dirty. The entire Main Frame was filthy and had a lot of sooty-greasy-type deposits everywhere. As this Main Frame will be reassembled with the EAC bed plate, everything has to be cleaned. The Main Frame is an important component of the R-390A and provides many of the ground connections for all of the modules. With all areas clean, all modules will be grounded together through the Main Frame.

Dec 2, 2022 - Main Frame Stuff - The bed plate from the ax-attacked EAC cleaned up fine. It was missing the left side vertical divider on the underside. Luckily, I had a nice condition one that I had removed a few years ago while recreating the R-725. On the "Blue Striper" Main Frame, the right side panel was rough, so I robbed the right side panel off of the Imperial "parts set" that was still out in the shop. I had to perform a little body work to straighten some minor bends. The lowest screw hole to mount the rear panel wasn't counter-sunk but the left side panel I'm using did have this hole counter-sunk. I used a counter-sink bit to make this hole into a counter-sunk hole. Takes a 6-32 FH screw with conical washer when mounting the rear panel. In most R-390A receiver's this hole isn't counter-sunk (but I wanted the two side panels to match.)

Main Frame underneath with EAC bed plate installed

Main Frame topside with EAC bed plate installed

Dec 4, 2022 - Function switch was missing the micro-switch. I replaced the entire Function switch. One wire broken off from the BFO switch terminal - repaired. AC to 3A fuse holder broken - repaired. Used DeOxit and a small paint brush to individually clean each rotary switch. Installed extensions for the Carrier Level meter wires that were cut short. Used correct coded wire from a junk harness. Attached using spiral TC junctions for splices that were soldered and then covered with shrink tubing.

Dec 5, 2022 - Finishing up the Main Frame - Installed the wire extensions for the Line Level meter using the same method of spiral TC junctions, solder and cover with shrink. Replaced the capacitor that mounts next to the CL meter with one from a junk harness. Had to redo some of the wires to the Local Gain pot (one was broken and the others were about to.) Detailed the wiring harness further to remove all of the greasy soot deposits. Checked the AC power cable and although it looked okay at a glance, the wire insulation inside was badly rotted. Replaced the AC power cable with a new one that was installed to have the hot and neutral wires inside the cover and only the cable and ground wire exiting. Nine of the terminal screws were missing and the four aluminum jumps necessary for normal operation were also gone. I harvested the screws and jumps from the "junker" Imperial out in the shop.

Dec 6, 2022 - Front Panel Work - The front panel I'm using was on the '67 EAC receiver that ended up with a NSA Black Anodized panel, so this panel was excellent and was only removed from its receiver so I could install the black panel. This panel only required dusting to be ready to use. The grab handles were installed. I installed the two meters. These both had the mounting hardware but no lock washers. Instead green Lok-tite had been used sometime in the past. I'll add lock washers. The Dial Lock mechanism was installed and the Zero mechanism was also installed. When doing the final front panel installation, the Dial Lock has to be loosened and turned about a half-turn to clear the dial lock wheel on the RF module. I decided to install extensions on the two BFO wires that obviously had been pinched for years between the front panel and the Main Frame. One wire felt like it had broken inside the squashed insulation. I used spiral TC junctions and shrink tubing for the splices. The three 1/4" shaft panel bushings were installed finger-tight. All of the switches and pots were mounted into the front panel. I used internal tooth small trim lock washers on all of the control mountings with good condition nuts (finger-tight only at this time.) The harness had to be moved slightly every so often to get all of the controls to fit correctly. This is normal when replacing a front panel. Back to finishing up the RF module,...

Back Panel cleaned and completed except for an AC plug (clip for plug holder gone.) Also, the IF output BNC isn't installed (I do have a good J116 to install.)

Cleaned up the residual WD-40 from the "brush and flush" operation. This gearbox was one of the cleanest I've done. And to think, it was almost destroyed by the "ax-attack" which did destroy most of the main frame.

The Veeder-Root counter that I installed was one that convenient to use. It wasn't in very good condition. So, I exchanged that Veeder-Root counter for one that was in excellent condition and rotated all of the number wheels easily. When installing the Veeder-Root counter, the mesh of the conical gears has to be adjusted by loosening the shaft clamps for both MC and KC, adjusting the position of the conical gear on each shaft for a good mesh (not too much though,) setting the proper numbers to show and then tightening the clamp. Too much mesh will result in some binding as the gears rotate. Just enough mesh for minimal backlash and easy rotation. 

Dec 9, 2022 - Removed all Vari-IF & RF slug racks. Removed all Vari-IF coils and all RF transformers. Cleaned the area of all sand and debris though there wasn't much. Lubricated all Oilite bushings with a drop of 3n1 oil (10w machine oil.) I found some of the roller bearings that are vertical guides for the slug racks were stuck and had to be oiled and rotated to get them turning freely. It's common for these small roller bearings on the vertical guides and on the slug racks to be stuck due to dirt and lack of proper lubrication. The vertical guides are bearings for straight side opposite the tapered edge on some of the slug racks. The roller bearings on each end of the slug racks rides on the cams. All roller bearings need to be checked for proper rotation and lubrication.

RF section - The same procedure is used here,...disassemble, clean and inspect each RF transformer before installing. De-Oxit used for the trimmer rotor contact and the plug-in pins. I installed the 16-32mc section first. The RF coils/transformers were installed as they were inspected and cleaned. Then the slug rack was cleaned and checked, then installed. Next, the 8-16mc section was installed in the same manner.

Dec 11, 2022 - Continued with the installation of the 4-8mc section in the same manner. The 2-4mc section was next. I found another 2-4mc ANT/RF transformer made by American Transformer Company in the upstairs storage area. It looks in very good condition with no apparent burns on the coil. I substituted this RF transformer for the Teledyne I was going to use. Then the 1-2mc section was installed followed by the .5-1mc section. The slug rack on the .5-1mc section was bent slightly and the guide roller bearing was misaligned. Straightened the slug rack frame to correct. All of the individual slug position adjustments were aligned for minimal rubbing of the slugs against the inside of the coil barrels. A couple of return springs needed a slight adjustment to the "hook" end so they would stay secured. The entire RF module was run from 00.000 to 31+000 to verify that all slug racks travelled without sticking or binding and that all of the roller bearings are rotating as they should. This completed the mechanical check-out and rebuild of this EAC RF module (with Teledyne Crystal Oscillator module.) The RF module needs to be installed and interconnected for the electronics check-out.

Next, I placed the RF module into the Main Frame. I tested mechanical alignment by lightly tightening the captive screws - then loosen them a turn to allow some movement. Then I installed the three side mounting screws. These screws have Ny-loc type pem-nuts installed so a lock washer isn't required but because the clearance hole is oversize, I use a flat washer on the five of the seven RF module mounting screws. Also, these seven screws should have green painted screws heads to identify that they are part of the RF module mounting. I had to paint a set of screws for this installation. Five screws are .75" length and two are .5" length with the two shorter screws used in the front two screws positions. Once I had all the screws loosely threaded, I then tightened the four captive screws, then the three side screws, then the two left side screws (one screw also mounts a harness clamp) and finally tightened the two front screws. All screws that thread into Ny-loc pem-nuts only require a flat washer. The two in front screw into regular pem-nuts so a lock washer is required. I rotated the KC and MC to make sure nothing was binding.  >>>

Once the front panel was secure, I turned the Main Frame/RF module on its side to allow access underneath. I then proceeded to tighten all five of the harness clamps. There are three on the front panel, one on the left side that uses one of the RF module mounting screws and one inside the PTO bay. There's also another harness clamp on the bracket that holds the antenna relays that needed to be tightened. The Dial Lock assembly was placed into position to allow it to clamp the locking wheel and then its mounting nut tightened. One more check to make sure everything had clearance and that there weren't any pinched wires.

This initial part of assembly that involves going over the Main Frame carefully and the detailed disassembly, inspection, cleaning and adjusting the RF module are the two most involved tasks that take the most time to complete. But, attention to detail at this initial stage will save a lot of time and work later on. So, with this most complicated work finished, the "receiver" is now ready for installation of the remaining modules.

I made a "tube scavenging run" out to the shop's upstairs loft where all of the bulk spare tubes are located. I did manage to find one NOS 6C4 so I can eliminate the "below minimum" 6C4 which should help performance. Came back with a load of 6AK5, 6AK6, 5814A and 6BA6 tubes, most NOS or, at least, in a box.

IMPORTANT NOTE: Unfortunately, it's very common to find a tube that's in an original box and the tube inside matches the box and looks NOS. Then, when testing that tube, you find that it only measures minimum acceptable transconductance. I know that many, many "repair techs" wouldn't toss out the old "minimum" tube but instead put it into the box that the new replacement tube came in. I don't know why or what the reasoning was, probably "emergency use" or something like that, but they never seemed to have taken the time to mark the box or tube as "weak." I've run into these types of tubes many, many times. It's why I NEVER buy a NOS boxed tube unless that tube has also been tested. Lots of eBay "amateur tube dealers" don't test their boxed tubes and assume since the tube and box match it must be NOS but only by testing is the actual condition of the tube known ("known" to the parameters that the tube tester can determine anyway.)

photo left shows the Frankensteinesque R-390A fully assembled looking at the bottom. Amelco AF Module at the top of the photo. The sticker is from McClellan AFB in Sacramento, California. In the middle is the Cosmos PTO showing this photo was taken before I replaced the Cosmos with the Raytheon PTO. The lower module is the Amelco Power Supply. Note how the harness is routed when all of the harness clamps are installed along with the front panel fully mounted.

IF Module - Installed the IF module. I'd gone thorough this IF module some years ago and was using it in the Capehart R-390A, so it's in good physical shape and should function fine. It might even be aligned. I'm still "rounding up" nice looking tube shields so not all tubes have shields yet. The shafts and clamps for the BANDWIDTH and BFO controls have to be installed before the IF module is installed. Once the IF module is in place and the captive screws snugged-up (not excessively torqued*) then these two control shafts are installed onto the module shafts. The panel bushings have to be slightly loose to allow placing the shafts in alignment. Once in alignment then the clamps can be tightened. Then the bushings can be snugged-up. The coaxial cables were then installed and then the Amphenol connector plugged-in to complete the installation. I have to find a spare IF OUTPUT cable that connects from the IF module to the back panel IF OUTPUT connector. Should be one in the parts collection in the shop.

* SNUGGED-UP -  I use the term "snugged-up" to illustrate my frustration at always finding all of the screws, no matter where used, tightened to the point of requiring special tools to loosen. All of the screws in the R-390A use lock washers that only need to be tightened to the point where the lock washer is just fully compressed. Some screws thread into Ny-lock pem-nuts and these screws only need to be reasonably tightened. Set screws for knobs are routinely found over-tightened to the point where the set screw galls the shaft making knob removal difficult, if the set screw itself can even be loosened. This is such a common problem that all rebuilders must have an array of "over-tightened screw" removal tools in their collection of "special application tools." Fortunately, many of the rotating shafts in the R-390A use clamps rather than set screws.

I also installed the five flat-head mounting screws on the lower left side of the front panel. Since these thread into standard pem-nuts a conical external-tooth lock washer has to be installed on each of these five screws. Also, the remaining six flat-head 8-32 screws that mount the front panel to the Main Frame were installed.

Another trip to the shop for "parts harvesting." Found all of the tube shields I'll need in an old junked Motorola police transceiver (nice ones.) I also ran across another boxed 6C4 that tested 70/55 on the TV-7 so it will replace the remaining "low" 6C4 that measured 59/55. Found an IF OUTPUT coax cable. Removed the Imperial data plate because it was the best original condition data plate that I have. Removed lots of hardware from the Imperial "parts set." Removed a set of knobs from the Imperial. Removed two sets of plug-in electrolytic capacitors. One set was in the Motorola "parts set" and the other set was installed in a spare AF module. Three caps passed their preliminary test but one failed miserably. If the three will reform, I should have a usable set for the AF module.

Cleaned the AF module, installed the tested tubes and installed the reformed multi-section capacitors. One note,...I was testing the 0A2 regulator tube not expecting anything other than the normal purple glow and the meter reading over 40. The 0A2 glowed bright purple and flashed repeatedly. The TV-7 meter was near full scale and fluctuating with the flashes. I hardly ever find bad 0A2 tubes but this one had all the indications of imminent failure. Replaced with a "tested-good" 0A2. Cleaned the PS module and installed the tested 26Z5 tubes. These two modules are ready to install. Only the PTO remains to be tested and calibrated before installation.

photo right shows the top side of the Frankensteinesque R-390A fully assembled,...well, the Utah plate and top cover aren't installed yet. Nearest is the Amelco IF module. In the middle is the Teledyne Crystal Oscillator and farthest is the EAC RF module.

PTO Testing - Since I have a test fixture for R-390A PTOs, it's very easy to check one out, do any adjustments that might be necessary and then, when satisfied with the performance, the "tested" PTO can be installed into the receiver. I selected four PTOs to test. The Raytheon rebuild, the Cosmos, a Collins and another unmarked PTO that was probably a Collins or Collins clone. The Raytheon had pretty good linearity with total error of about 4kc. The Collins was also fairly linear with a total error of about 4kc. The Cosmos had the best linearity staying within 2kc and a total error of about 2.5kc (actually it was a 5kc linearity error.) I didn't test the unmarked PTO. I installed the Cosmos PTO into the receiver (replaced with the Raytheon 12/28/22.) The PTO shaft will have a fiber bushing for the correct diameter for the Oldham coupler face piece. This has to be on the PTO shaft or the coupler face won't fit correctly. To ease installation, lightly grease one side only of the Oldham disc. That will keep it from falling off while the PTO is placed into position. Clearance is very tight and sometimes it helps to loosen the mounting screws for the rear PTO mounting bracket to allow a little more clearance while fitting the PTO into position. After the PTO captive screws are snugged-up then tighten the rear PTO mounting bracket. The coax from the PTO connects to the RF module routed through the hole in Main Frame bed plate. The power cable for the PTO comes from the PTO bay harness with an obvious connection.   >>>

The audio really got loud if the unused Diode Load terminal wire was physically moved a bit. It seemed to be in the harness. The Diode Load wire entered the harness next to one of the panel harness clamps. It appeared that the clamp was pinching the wire bundle due to the additional Diode Load wire that was actually a shielded cable. I took off the harness clamp and cut the Diode Load cable back to the next fabric harness cover. I then cleaned the wire bundle where the pinching seemed to be happening. Then wrapped the wire bundle with several layers of friction tape to make some padding. I then reinstalled the cable clamp. After completion, the audio output remained at a high level and didn't change if the harness was moved. It's unfortunate that this "Blue Striper" harness was the only complete harness that I had. All of my other harnesses have been "chopped" by scrapers or destruction technicians.

In checking visually only (not a good thing to do) I cut a wire that was on the rear terminal for the LOCAL OUTPUT assuming it was a mod. After checking the schematic, I found out I had cut the return wire from the PHONE jack (connects the phones through a resistor to ground.) Used a spiral TC junction to solder splice the wire back together.

Completed RF alignment with no issues. I connected the 135' tuned Inv-Vee set for 20M and tuned in a VK5 from western Australia on 14.195mc who was very strong and had quite a "pile-up" going on. Heard all of the stations calling with most being from USA midwest. WWV on 15mc was 4kc low but I haven't cal'd the dial, very strong. This was just a "quick alignment" to find any problems. The receiver works pretty well but I can tell it's had a lot of wear in the switches on the front panel with that being the fault of the harness from the "Blue Striper." But, considering it's a history at St. Julian's Creek Annex, I guess I'm lucky it even works.

Dec 21, 2022 - For the most part, the "Parts Set R-390A" is done. There's still some fine tuning and little mechanical tasks to be finished. I'll certainly do a black lacquer "touch up" on the knobs and leave just a little of the wear showing. Any interesting developments will be added below as "UPDATES."

Boneyard Parts Sources Used - This R-390A ended up with a Main Frame that was built-up using some of the "Blue Striper" parts (the harness and the back panel plus the left side,) the bed plate from the "ax-attacked" '67 EAC and the right side panel from the '63 Imperial. The front panel is from a different '67 EAC. The RF module is from the "ax-attacked" '67 EAC. About half of the RF transformers and coils are American Transformer Co. with the other half being EAC units. The Crystal Oscillator is a '62 Teledyne parts module but the crystals came from the "ax'd" '67 EAC C-O. The IF module is a '62 Amelco pre-aligned and used module that had been in a '61 Capehart. The AF module is a '62 Amelco parts module but the multi-section filters were from a parts Motorola AF module. The Power Supply module is a '62 Amelco parts module. The PTO is a Cosmos of some vintage from the spare PTO collection (replaced with a Raytheon rebuilt PTO on Dec 28, 2022.) The knobs were mostly from the Imperial "parts set" but a few were harvested out of the spare knob "parts bag." The receiver is mostly Teledyne-Amelco-Imperial parts and modules along with some EAC parts and an EAC RF module. It seemed appropriate to install the '63 Imperial Electronics Inc. tag from the Imperial "parts set."

Received Trenton Military today on 15.035mc USB with air weather out of Trenton, Ontario. Signal was about 5 by 6. Also, heard a ZS6 working several state-side stations on 20M. His signal was easily 5 by 7. It's normal for a receiver to improve in performance somewhat with use after a reworking like this one has had. All of the modules have been setting around for years without power and probably were thrown around during any moving that happened. Same with the NOS and "test good" tubes - they've been setting around for years with no power on them, just setting in a box,...aging. As all of the components and mechanics get back to actually "working," things tend to improve over the next few days to a week or so. Since, the receiver seems to be performing quite well I'm going to pull the PTO out and do the EPE adjustment. This PTO had about a 2kc EPE which isn't terrible but the linearity was off some in the middle of the range. Usually, if the EPE is set to minimal error then the linearity is also improved.

1967 Electronic Assistance Corporation R-390A SN: 974 - Restoration Log (2016)

This was my first "journal-type" of write-up from about seven years ago now. That's why the explanation that follows,...

The following write-ups are little different from my usual restoration write-ups. I've written this one in the form of a journal or log that has daily input as the project progresses. I hope this approach gives the reader an idea of the order in which the restoration-rework takes place and the problems encountered along the way as the work progresses. It will also show the reader about how long it takes to complete an R-390A that isn't in terrible condition but certainly was non-operational and incomplete.  - H. Rogers, Aug 2016.

July 17, 2016 - Once I got the R-390 home I was able to inspect it more thoroughly. Mike was right,...all of the crystals had been taken out of their sockets. There should have been 17 crystals and all were missing. The cover had been screwed down so tightly, I thought that nobody had been in there,...ever. Also missing was the 4-8mc RF-Ant transformer, the 4-8mc slug rack and slugs, all of the tubes in the RF deck, top and bottom covers, the Utah plate, the front panel bushing for the KC tuning. Both meters were non-original types that were similar types but not correct. On the good side,...the dial had a security flip-down dial display cover, the 3TF7 was good, both 26Z5 tubes were present (and tested good,) the receiver was a 1967 EAC contact with the correct data plate and all of the modules were correct EAC with the correct contract number on each module. None of the sheet metal was "bashed" and, mechanically, everything looked okay. Luckily, I had a couple of "parts sets" and extra modules so the missing parts weren't going to be too much of a problem. The receiver was extremely dirty with loads of greasy, oily contamination that had very fine black powder mixed in. The receiver had obviously been stored in a garage or machine shop or some other location where oil and fine black powder would be everywhere.
 

July 20, 2016 - Started complete tear-down. All modules out, front panel off, all parts plastic bagged and tagged.

Complete disassembly of the Main Frame was necessary because the oily dirt had worked into the side panel joints due to loose screws. Again, under the dirt everything was in excellent condition.

August 1, 2016 - Tested the two can electrolytic capacitors and found the triple-30uf to have one defective section. The dual-45uf seemed to reform okay but the values are not very close. Same with the two good sections on the triple-30uf. I will have to rebuild these two units using new electrolytic capacitors for best reliability and performance. I had several spare R-390A can electrolytics and when testing them I found that ALL were defective in some way. Probably time to admit that you can't use and reuse the original, fifty-year-old caps anymore. New electrolytics ordered and on the way.

August 2 - 6, 2016 - While waiting for the replacement electrolytic capacitors, I tested all of the tubes and cleaned the tube sockets on the IF module and re-installed it into the Main Frame. I also had to locate tubes for the RF module since all were missing. The other modules all had W.P.M. heat-reducing tube shields so I also needed to find tube shields for the RF module tubes. All I had was IERC-type, which are very good heat-reducing tube shields, but they don't look like the W.P.M.-types. Since most of the tubes in the RF module are covered by the Utah plate, I went ahead and used the IERC-types.

August 8 - 11, 2016 - Rebuilt the two multi-section electrolytic capacitors. Photographed for the added write-up on this procedure that is now in this web-article in the Audio Module section. Picked up four NOS 6DC6 tubes from Ham & Hi Fi. Installed the remaining modules into the main frame.

Since I didn't set the Veeder-Root counter to XX.000 before removing the RF module, the PTO was not pre-set to 3.445mc. This is a minor inconvenience that requires the PTO be set by powering up the R-390A and measuring the frequency out of the PTO with a digital frequency counter. The procedure I use is above in the PTO section of this web-article.

Since I had already powered up the R-390A, I went ahead and hooked up a 600Z ohm speaker. I had lots of noise but the calibrator seemed pretty weak on 40M. I connected an antenna and tuned around 40M and heard a few SSB stations. Now this R-390A has been completely apart and is certainly quite a bit out of alignment but still it picked up a few signals. This should be a very good sign of things to come.

August 18-20, 2016 - Peaked the mechanical filter inputs and outputs. This requires having the IF module dismounted but still connected to power. Photo and method described in "IF Module" section further above in this article. All mechanical filters were pretty close so, just minor tweaking.

August 21, 2016 -  Completed the full alignment. Most adjustments were pretty close but, as expected, the 4-8mc section was quite a bit out of alignment. Installed the Utah plate, top and bottom covers. Connected receiver to the full-size ham antenna. 40M reception is normal now. All other bands are functioning correctly. Adjusted Carrier Level Meter and IF Gain for best performance.

1. Components - many ceramic disk capacitors in RF and IF modules. These modules also have several capacitors that appear to be metalized film capacitors. The AF module appears to have similar capacitors to the old Vitamin-Q types but I think the construction is different with better seals. Certainly the multi-section filter capacitors are of the same construction and questionable reliability. They have the same problems that are found in any multi-section electrolytic capacitors that are half-a-century old. Overall, the most of the capacitors seem to be better types than those used in the R-390As built in the 1950s. Cosmos PTO is difficult to adjust the EPE due to the new location of the L701 adjustment behind Z702.

2. Performance - is definitely equal to a rebuilt and recapped earlier version receiver. IF Gain is set at about 60% which is pretty close to where it's adjusted on the recapped earlier versions. With IF Gain set at 60%, most SSB signals demodulate nicely with the RF Gain at about 5 to 7 and the AF Gain at 7. This is using a 135 ft center-fed tuned inverted-vee antenna. SW BC stations usually run about 50 to 60db on the Carrier Level meter depending on the station and the time of day. The coupling capacitors in the AF module were NOT changed to .02uf but the audio sounds very good with noticeable bass response on AM BC and SW BC. Also, strong SSB stations and AM ham signals seem to have good bass response with the original .01uf coupling caps. Overall, a nice performing R-390A that is going to be set up with one of my ART-13A transmitters for awhile.

Time to Complete Project - It took just about one month to complete the rework on the 1967 EAC. This is from a non-operational, incomplete receiver to an entirely functional and totally complete receiver. I didn't work on the receiver everyday so total time actually spent on the project was probably around 20 hours.

Update - Sept. 4, 2016 - I guess I should have cleaned the Antenna Input relay contacts. The procedure is described in the Main Frame section further up this page. It's not difficult to do, even if the receiver is already back together. The symptoms were no (or very little) carrier level indication, a change in the normal position of the ANT TRIM for resonance and relatively weak signals. If STAND BY or BREAK IN were actuated then the signals would return to normal levels. This was the typical indication that the antenna relay contacts were introducing some resistance due to poor contact. In this particular case I don't believe the cause was oxidation because inside the arm, NC and NO were very clean looking. I used just a slight bit of DeOxit and paper to clean the contacts to have them measure zero ohms. Problem might have been some kind of rosin-like coating or something that dissolved with DeOxit. Other than this minor and easy to correct problem, the '67 EAC R-390A has been performing very well.

Update - March 7, 2018 - Read "Creating an Authentic Arvin R-725/URR" in Part 3 to see what's happened to this '67 EAC R-390A. Here's a quick link R-390A Part 3

Not Another 1967 EAC Restoration Log?  (2017)

When I got the R-390A home, I had to investigate that yellow power cable and 600Z ohm transformer. The yellow cable certainly wasn't original but its installation didn't do any damage either. Same with the 600Z transformer that was utilizing an existing stud for mounting. While looking at the back panel I noticed "Electronic Assistance Corporation" with the "FR-36-039-N-6-00189(E)" order number and the "DAAB05-67-C0115" contract number stamped on the back. I then looked at the Crystal Oscillator (attached to the RF deck) and saw the same stamping. I noted that the electrolytics on the Audio Module were date-coded "67." So, I pulled out all of the modules except the RF deck and to my surprise they were all 1967 EAC modules on the FR-36-039-N-6-00189(E) order and DAAB05-67-C0115 contract from 1967. This receiver was a 1967 EAC R-390A that for some reason had an Imperial Electronics tag installed. Further inspection revealed that the receiver was nearly complete and original. The only missing parts were the correct ID tag and the "Utah plate."

Although I had originally thought when purchasing this R-390A to use it as a parts source for my 1961 Capehart (with OD front panel) this one is just too nice and original for that purpose (the Capehart will just have to wait.) I'll get started on this '67 EAC during the summer and write a restoration log as I proceed along with the rebuild.

June 12, 2017 - Started on this EAC. I had already obtained an original Utah plate and a repro '67 EAC data tag. All the modules except the RF module had been pulled and were setting with the receiver. I started with the IF module, the AF module and the Power Supply. Each module was cleaned and the tubes tested. Any weak tubes found were replaced. The two electrolytic filter capacitors were reformed. These capacitors were date coded 1967 and both checked okay. Reforming seemed normal with the two 40uf caps drawing about 10uA after reforming at 280vdc and the three 30uf caps drawing about 15uA to 25uA at 280vdc after reforming. The final test will be to see how the filter caps perform in the receiver. I didn't have very good luck with the last EAC receiver's filter caps which had to be rebuilt. These filter caps seemed to form nicely but performance is the final test.

June 13, 2017 - Completed cleaning and tube testing on the above modules. I had to double-check the wiring on this EAC power supply as the wiring didn't look like most PS modules. Though the wires were not "tucked" under the chassis, as is normally done, the wiring was correct. Just an anomaly of that particular PS assembler and final inspector. I had to replace all of the 5749 tubes in the IF module since they all tested weak. They were all RCA-JAN brand and date coded 1965. Also, one 5814A in the IF deck needed to be replaced. On the AF module I replaced one 5814A. Both 26Z5 tubes checked okay in the PS module.
 

CONTINUE TO PART 3