BUREAU OF ENGINEERING
The RAA B&W from the US Navy Equipment Catalog
|A "cost no object" relationship existed between RCA and the U.S. Navy. Maybe it was because RCA was created at the request of the Navy in November, 1919. At any rate, many of the early Navy-RCA receivers are "over-the-top" in heavy-duty construction, sheer-size and weight, circuit design and performance. The RAA receivers were the first longwave superheterodynes built for the Navy. Even though produced during the depths of the Great Depression, RCA's extravagance when designing for the Navy is evidenced by the RAA. This article is mostly a restoration log that is written as the work progresses rather than trying to remember all of the details after the project is finished. This format allows those interested in the process and problem solutions to follow along as the restoration evolves. This restoration log-web article will be updated at least once a month as the project progresses. H. Rogers - June 2017|
The U.S. Navy RAA receiver was first produced in 1931. The initial
versions, RAA up to RAA-2 (1934) were built by RCA-Victor Corporation
but, by the RAA-3 (1935,) RCA
Manufacturing Company, Inc., a division of RCA that handled most of the
commercial and military contracts, was the builder. As RCA expanded
their radio-dominance in the thirties, they created several divisions
within the corporation to handle specific parts of the business.
Radiomarine Corporation of America had been created in the mid-twenties
from Wireless Specialty Apparatus Company after their acquisition by
RCA. Radiomarine Corporation handled all of the commercial shipboard radio
equipment sales, service and also ran many of the coastal ship-to-shore
stations, becoming a powerful subsidiary of RCA.. RCA Manufacturing
Company, Inc. was created in the thirties after the 1930 anti-trust suit
settlement essentially recreated RCA into the "Radio Corporation"
that the Navy had originally envisioned in 1919. Since commercial and military
contracts were becoming a large part of the radio business, RCA
internally separated the primary business, RCA-Victor, as the entertainment
radio-phonograph-recording-broadcasting division and RCA Manufacturing Company for
commercial and military radio equipment building.
The 1931 RAA was the first longwave receiver that utilized the superheterodyne circuit. Prior to the RAA, the most commonly used commercial shipboard receiver was the Radiomarine Corp. IP-501A. Also found on ships and at shore stations were the many SE-1420/IP-501A versions along with the many variations of these models of receiver. The SE-1420 receiver design dated from late-WWI but the performance was so good that contracts were still being issued and built-on even into the late-twenties. The Navy was also using SE-1420/IP-501A types of receivers in the twenties. By the late-twenties, more modern RA, RE, RG and their variations were used by the Navy. These receivers were somewhat more advanced but used plug-in coils and had regenerative detectors with audio amplifier stages. Regenerative detector receivers were considered by shipboard radio ops to be the most sensitive yet simple receivers for use at sea where simplicity equated to reliability or ease of repair.
Recent History of RAA-3 SN:64 - I received an e-mail from Robert Goff W7MKA in Grants Pass, Oregon wanting to know if I'd be interested in restoring an early Navy LW receiver, the RAA. Robert wanted to donate the RAA if I would perform the much needed restoration. During to course of our e-mail exchanges, it was suggested that Bob Welch W6AQU, who is a mutual friend and who happened to live not very far from Robert, bring the RAA down to the upcoming N7RCA Minden, Nevada swap meet in June. Actually, the swap meet was several months away but that was just one of a couple of options suggested for transportation. A few days before the June 17th 2017 N7RCA swap, Robert transported the RAA to Bob's QTH and the two of them loaded it into Bob's truck. At the N7RCA swap on Saturday, I met up with Bob who had actually driven the six-hour trek Friday afternoon. After the swap meet was winding down, KØDWC and I unloaded the RAA from Bob's truck and loaded it into my Toyota FJ (with the rear seats folded down.) Later that afternoon, Chuck KØDWC came over to my QTH in Dayton and we moved the RAA from the FJ into the shop. As a thanks to Bob W6AQU for bringing the RAA over to the N7RCA swap, I gave him a restored Hallicrafters SX-28 receiver.
Robert W7MKA told me that the RAA had been up in Eugene, Oregon for years. It seemed that a retired professor from SOU had purchased a large piece of property off of the Loraine Highway in Eugene. The property had lots of old growth trees, one trailer and piles of stuff scattered around the property, including the RAA. It seems that the RAA had been wrapped up in a tarp and was stored outside. Robert obtained the RAA from the professor who only wanted a "scrap metal" price for it. How the RAA originally got to Eugene and why it was stored on the property there was unknown to Robert.
|WWII History of
RAA-3 SN:64 - When pulling the tubes to begin major
disassembly, I discovered two important clues as to the SN: 64 location
and use, at least during WWII. The RF Amplifier tube is well-protected, double shielded
with a standard aluminum tube shield and the threaded cap
shield that's on the Tuner band switch box shield. When pulling the Type
58 tube, I noticed that there was a label on the tube that read "U.S.S.
WHITNEY" with tube test data and two dates. The first date was
ink-stamped "7 OCT 1941" and the second date was in pencil " 7 / 6 / 44"
with penciled test data. There is an early label under the Whitney label
that has pencil written test data but no date. This label though must
date from before October 1941 indicating that the tube, a Sylvania 58,
is a pre-WWII installed tube.
Loose in the tube shield was another tag (very faded) that read "U.S.S. DIXIE, RADIO SHOP, Tested, Date." If there was any data written after Tested or Date it was faded beyond reading. So what do these labels indicate? All of the other tubes in the RAA-3 were WWII issue USN tubes with no labels. Only the pre-war Sylvania had a label.
The Ships - The U.S.S. Whitney and the U.S.S. Dixie were both Destroyer Tenders. Destroyer Tenders were large "repair" ships that were assigned to a flotilla of Destroyers. Since Destroyers were small ships with limited crew facilities, the Tenders not only provided most types of repairs but also provided dining facilities, electrical power when needed, refueling when needed, water desalination (showers and flushing needs,) Destroyer crew quarters when needed and many other support duties for the Destroyers in the flotilla. Both the Whitney and the Dixie had radio repair shops and stores of spare tubes and spare parts. Since both labels indicate radio repairs (or servicing) by the Whitney and the Dixie, it seems possible that RAA-3 SN:64 was used onboard a Destroyer before and during WWII.
photo above: This label is very faded but the top line is "U.S.S. DIXIE," the second line is "RADIO SHOP," the third line is "Tested" and the fourth line is "Date."
No other tubes in the receiver had tube test labels left on them (but the Power Supply does.) All of the other tubes were WWII USN tubes. The RF Amplifier tube was the only pre-war tube and its early date is actually before Pearl Harbor was attacked.
|More Tube Labels
- I started to disassemble the Power Supply on July 8, 2017. There are
three tubes used, two Type 5Z3 and one Type 874. All three tubes have
test labels and all three are from the Repair Ship AR-1 U.S.S. MEDUSA.
Two labels have easily readable dates. One 5Z3 had two labels one on top
of the other. Both labels had readable dates and both were from the
MEDUSA. The two labels are shown to the right. Note the the early label
is dated 5/2/42. The later label is dated 6-20-45, almost at the end of
WWII. The other readable label is on the 874 tube and it is dated
6-28-45, indicating that probably all of tubes were tested as part of
servicing. However, since the Power Supply doesn't have a matching
serial number to the RAA-3 SN:64, we can't be sure that this power
supply was actually used with the RAA-3 during that time period (WWII.) It's
probable that while servicing or repairing the receivers, power supplies
were interchanged since the power supply is specified for use with
either the RAA or the RAB receivers and can also be used with all
versions of either receiver. If used with the RAB-1 there's a toggle
switch inside the power supply that must be switched to the RAB-1
position. In the opposite position, the power supply works with all
versions of the RAA or the RAB, RAB-2 thru 4. Suffice it to say,
although the power supply tube labels are certainly interesting, their
direct connection to the RAA-3 SN:64 receiver cannot be confirmed.
The Ship - The U.S.S. MEDUSA was a Repair Ship. These ships were like Destroyer Tenders but a little larger and not specifically assigned to Destroyers. The Medusa would do repairs on any type of ship. The same type of repair facilities were on Repair Ships and the Radio Repair Shop was well-stocked with repairmen, tubes and parts. The Medusa was assigned to the South Pacific in 1944 and 1945. Likewise, the Whitney and the Dixie were Pacific ships. In fact, the Whitney was docked at Pearl Harbor on December 7, 1941 but came thru the attack undamaged. It seems likely that RAA-3 SN:64 was in the Pacific, probably for all of its service life and certainly just before and during WWII.
All of the photos in the following section are of RAA-3 SN: 64 before any restoration started. Some minor cleaning was done as part of the inspection process.
Radio Frequency Tuner - The RAA receiver uses a Tuner Section that employs an Antenna Input section that has selectable coupling (close or loose) to the RF amplifier stage that uses a type 58 tube. The Mixer is a type 24-A tube and the LO is a type 56 tube. The impressive tuning condenser consists of ten sections that are paired together to provide a five-gang air variable that is 27 inches long. Each of the five sections are located in its own shielded compartment. The tuning condenser is driven by a brass worm gear and a fiber wheel gear. Each coil used in the tuner is housed in a shielded compartment or is shielded with a screw-on shield can. The Tuner covers from 10kc up to 1000kc in five bands. Power to the tuner comes from the Power Supply and is routed via a cable that connects to a terminal strip located on the right side of the chassis (viewed from rear.) The IF-AF Unit is connected to the Tuner via a shielded cable that is connected to a terminal strip located in the LO section of the tuner. The output signal (at the proper IF) is routed down this cable to the IF-AF Unit where the proper (matching) band is selected by the IF-AF bandswitch to provide the correct IF section where then the Tuner IF signal is amplified, detected and audio amplified..
Since four separate IF stages are used for the five tuning ranges, the Tuner LO has to combine with the incoming tuned RF signal in the Mixer stage to output 37.8kc for bands one and three, 20kc for band two, 95.5kc for band four and 238kc for band five. The band switch uses a set of 90 degree gears to drive the multi-section band switch that has each switch-section within a shielded compartment.
The chassis, the shielded compartments, the brackets, the cabinet and most hardware is made of nickel-plated brass. The front panel is made of .25" thick aluminum that measures 27.5" wide and 20.5" tall. These non-ferrous metals were used to reduce corrosion from salt-air environments found onboard ships at sea or at shore stations.
photo above: Not many receivers have a tuning condenser that's 27" long with ten air variables set up in pairs for a five gang tuning condenser.
photo above right: The data plate of the RAA-3 is mounted on the Tuner front panel. Note the contract date of 2 Nov, 1935. Serial number is 64.
photo lower right: The tuning dial is miniscule and not illuminated. It uses the 0-100 vernier and the 0-10 course dials. The chart frame holds the tuning chart. I have the original tuning chart, a penciled chart and a "blank" chart.
photo right: Nomenclature plates for the Antenna input. Note the large studs for connecting antenna and ground. The broken shaft operates a switch for changing the Coupling from Close to Loose. I have the rest of the wooden shaft and the original knob. The control on the right is the band switch. This control operates a right-angle gear that drives the multi-section band switch that is mounted parallel to the front panel. The tuning range is shown in kilocycles for each band.
|photo left: Back view of the RAA Tuner showing the band switch compartments towards the front panel. The shield for the Antenna Input section is missing. The three threaded cylindrical shields on top of the shielded compartment are for the three tubes in the Tuner section. Nine coils are on top of the chassis and are located under the cylindrical shields. Seven coils are under the chassis and are located in individual compartments. The five compartments of the shielded band switch also have coils. Power is applied to the Tuner from the Power Unit cable harness that connects to a terminal strip located at the front right side of the chassis (as viewed from the rear.) There is also a shielded cable that comes from the IF-AF Unit that connects to the terminal strip at the LO section of the band switch compartment. The terminal strip can been seen as an opening in the shield near the front panel. There is a metal shielded housing that covers the terminal strip that is missing. Fortunately, the IF-AF unit also has the same type of metal cover so a replica can be made for the Tuner.|
|The Original Tuning Chart
and Navy Radio Stations - The original tuning chart has
survived with this RAA-3 receiver and is shown to the left.
NSS was "radio central" for the U.S. Navy and was located
at Annapolis, Maryland near Washington D.C.
NPL was at Point Loma near San
NPG was at Mare Island Naval
Shipyard located in the northern part of San Francisco Bay.
was located at Truckerton Island, NJ and was mainly used as a backup
station for the North Atlantic. NBA
was located at Balboa, Canal Zone (Panama.)
was located at Pearl Harbor, Hawaii.
These Navy stations were monitored by Navy ships because many orders and other important information originated at the Navy Department in Washington D.C. where it was usually transmitted by NSS to NPL or NPG and then relayed by NPL or NPG to NPM where the orders or info were then transmitted to the Navy ships in the Pacific.
Shown to the right is the original tuning chart from RAA-3 SN:64. The numbers immediately after the station call is the station's frequency in kilocycles. The TUNING column shows where to set the tuning dial with the band switches set to the proper kilocycle tuning range. I haven't been able to find out what "CCT TIMES" means. Various other kilocycle frequencies versus tuning dial readouts are also provided.
|Scrap Test Log
- Another interesting scrap of paper was in the same envelope with the original tuning
charts and is shown to the left. It's likely that this is a note of some
stations that were tuned in while the RAA-3 was either being tested or
repaired. Unfortunately, since it was just a scrap of paper, it
wasn't dated. However, it's possible to estimate an approximate time
period from the stations listed.
CMX from Havana was on 900kc from the late-twenties to the early forties. CMX was affiliated with NBC in the thirties. In June 1943, Cuban Socialists bought CMX and it became Radio Mil Diez using the call letters CMX for their 1010kc broadcast station. Radio Mil Diez was on the air from 1943 to 1948. Tuned on 9-48, Band 5 (approximately 990kc on tuning chart - see NOTE below)
WIBW in Topeka, KS was on 580kc (and still is.) The station ran 5000 watts in the forties. Tuned on 4-20, Band 5 (580kc on tuning chart)
KFAB was on 780kc before 1948 and was located in Lincoln, NE from the late-twenties until 1948. KFAB moved to Omaha in 1948 and changed frequency to 1110kc. Tuned on 7-30, Band 5 (approximately 790kc on tuning chart) NOTE: KFAB is tuned about 10kc higher than assigned frequency. Another 120kc to 900kc CMX and the tracking error could easily be 90kc. It's likely that CMX tuned is the 900kc pre-June 1943 station. The stations listed date this note certainly to no later than 1948. High-end tracking error probably accounts for tuning CMX 900kc at 990kc and likely dates this note to before June 1943.
photo above: The front panel of the Intermediate and Audio Frequency Amplifier. The hole in the panel is for the Plate Voltage meter (which is missing.)
Intermediate and Audio
Frequency Amplifier - There are four separate IF
amplifiers that are selected with the band switch on the front panel.
When setting up the Tuner a particular tuning range will be selected.
The same range must be selected on the IF-AF Unit which provides the
Tuner-Mixer with the proper IF for its output frequency. Two IF
amplifier stages are employed but, since there are four separate IF sections, there are twelve IF transformers in the
Since there are four different IFs, there must be four different BFOs
also. Total of sixteen transformers that are mounted under the chassis
in individual compartments.
The Automatic Volume control is actually an audio output limiter that provides some protection from heavy static or nearby lightning discharges. The Sensitivity control adjusts the level of RF and IF amplification. The toggle switches are top, AVC - ON - OFF. The middle switch is C.W. or I.C.W., indicating continuous wave or interrupted continuous wave. I.C.W. was a mechanical way to use a "chopper" (a rotating wheel that had alternating conductive and non-conductive segments) which would break the CW at a rate that produced an audio frequency interruption. This was to allow reception of CW without a heterodyne generator at the receiving end (a BFO or an oscillating regenerative detector.) Generally, I.C.W. will have the "chop" produce a frequency shift of the carrier (usually several hundred kilocycles shift.) I.C.W. was replaced with MCW or modulated CW which essentially is a transmitted carrier wave modulated by an audio tone oscillator. MCW used a much narrower slice of the spectrum than I.C.W. did. If an AM Voice signal was to be received, then the switch was placed in the I.C.W. position which turned off the BFO. The bottom toggle switch is the Audio Filter - Broad or Sharp. This is a 1000hz audio bandpass filter that was used to limit interference by reducing the bandwidth audio frequency response specifically for CW tone. The Sharp bandwidth is about 100hz.
The RAA receiver was primarily for CW (or ICW-MCW) reception. Although it would easily receive AM-Voice signals and was specified to do so in the manual, the typical shipboard use was for CW (nearly all Navy radio operation was CW until after WWII.) The audio output response is 200hz to 4000hz in Broad and about 950hz to 1050hz in Sharp. The audio output impedance is nominally 600Z ohms and intended for 'phones since the audio power is only about 500mW. The meter monitored the +200vdc plate voltage and also served as a power-on indicator. The circuit uses eight tubes which when combined with the three tubes in the tuner and the three tubes in the power supply brings the total tube count to 14.
photo above: The IF-AF nomenclature plates. The Automatic Volume control is actually an output limiter control. Sensitivity controls the grid bias on the RF amplifer tube and the IF amplifiers. Note the Frequency Band switch for selecting the proper IF section.
photo right: Under the IF-AF chassis showing the twelve IF transformers and the four BFO coils (rear-most coil set in each section.) Band switch is in the center of the chassis.
photo left: The top of the IF-AF chassis. The IF-BFO-DET tubes are located under the shield cans. The Audio and AVC section is at the top with four un-shielded glass tubes. Although not readily apparent in this photo, the Audio-AVC chassis can be dismounted from the chassis and the wiring harness disconnected. This may have been for ease of maintenance or construction. The shielded cable (that I'm holding) is routed to the Tuner unit through cabinet holes and connected to the terminal strip at the LO on the Tuner. The RF output (signal) at the selected Intermediate Frequency travels down this shielded cable where the proper IF must also be selected at the IF-AF unit for the signal to proceed thru the IF and onto the Detector and AF output. This cable is severely damaged and will have to be rebuilt. Surface rust is obvious on the ferrous-metal parts. The nickel-plated brass parts are in decent condition.
I've tried using a brass brush on the corrosion on the bypass capacitor cans in the foreground of the photo to the left. This easily removes the corrosion and the metal is in pretty good condition afterward. The corrosion is mostly surface type and hasn't "rotted" the metal.
Power Unit - The power supply uses two rectifier tubes. The power supply operates on 110vac to 120vac. In the CRV-20016-A version that was used with the RAA-3 and RAA-4 along with the RAB HF receivers the rectifier tubes are 5Z3 types. Earlier power supplies used type 80 tubes. The high plate voltage is +200vdc. An 874 cold cathode regulator tube is used on the +90vdc supply. Other voltages are +75vdc and +48vdc. Bias voltages are -1.1vdc, -1.8vdc and -3.3vdc. Power is supplied to the RAA-3 receiver via two large power cables with one cable connected to the Tuner and the other cable connected to the IF-AF section. The CRV-20016-A version has a multiple tap primary on the power transformer. The terminals are 1 for AC Line 1, 2A for 110VAC, 2B for 115VAC and 2C for 120VAC. At present the primary is set up for 115VAC operation. I'm going to utilize the 2C terminal for 120VAC input which is closer to my line voltage and will have the power transformer secondary windings operating closer to the specified voltages.
- The RAA-3 cabinet is actually two units bolted together. The Tuner
cabinet is 27.5" wide and the IF-AF cabinet is 10.25" wide.
When assembled together the cabinet measures 37.75" wide, 20.25" tall
and 21.60" deep. The cabinet
is made out of nickel-plated sheet brass to reduce corrosion from
salt-air. This probably helped to protect the wrinkle finish paint from
"lifting" due to corrosion under the paint.
The first impression is that this cabinet is made out of aluminum however that impression vanishes when one tries to move the cabinet. IT IS HEAVY!
The Tuner side has guides at each bottom corner. The IF-AF side has a centrally-mounted guide on the top and on the bottom. The edge of the IF-AF chassis slides in this guide keeping the unit in position so the thumbnuts can be tightened. There are entry holes for the power unit's cables. The entry hole for the Tuner can be seen. The entry hole for the IF-AF unit is in the upper right part of the back panel. There is also a hole thru the sides that are mounted together. This allows the shielded cable harness connection between the IF-AF unit and the Tuner LO. There are holes in the bottom that indicate that shock-mounts were probably originally bolted there.
The two cabinets will have to be "unbolted" and separated. This will allow for easier moving and more thorough cleaning, surface prep and repaint.
Inspection - June 18, 2017 to June 23, 2017 - No doubt, this is a formidable
There is a lot of damage due to poor storage conditions. This damage is
both cosmetic and electronic. With a project that requires this much
work it helps to create a list of problems and observations that will help to formulate a restoration plan. Here's the obvious,...
1. Entire repaint will be required. Black wrinkle finish - I'll have to contact VHT to see if I can buy a quart and then thin to spray using the larger paint equipment I have (the type for painting cars.)
2. Cabinet straighten and repair. Whatever the mounts were, they are missing.
3. Corrosion removal. Most is surface corrosion however some erosion is noticeable on the inside of the front panels where the mounting brackets contact the aluminum. Erosion on the back of the Tuner panel is pretty serious.
4. Wiring harnesses will require rebuilding. I'll try to use as much of the original wire as possible but it's probably going to be necessary to replace a lot of wires.
5. Data plates and nomenclature plates need restoring. Fairly easy.
6. Dial doesn't rotate although tuning mechanism works. Shaft turns so dial set screws are probably loose. Dial is held by a threaded boss and nut. The nut was loose.
7. Missing Plate Voltage meter - wiring to meter cut very short. Same Plate meter that's used on the early RBA, RBB or RBC receivers. The metal housing versions of the meter.
8. Broken shaft on Coupling switch control. I have the original broken shaft and knob. The shaft is made of wood so a replacement is fairly easy to construct.
Here's some of the other problems,...later update notes are in italics.
1. Several IF transformers are damaged, some minor,...one major. Appears that mice running around in the compartments broke several wires from the coils to the terminals of the IF transformers. One coil on one of the 238kc IF was bitten into and about 20% of the coil is missing. This one will need to be rewound or a replacement coil from a 200kc IF trimmed to work. Too bad someone removed the bottom shields years ago. >>>
>>> 2. Severe nut and seed storage in LO section of tuner - no apparent damage after removal. Used a shop vac (there was a lot of seed/nut debris - see photos below.) One terminal on the bandswitch is broken.
3. IF Bandswitch doesn't rotate - appears shaft is corroded in one bearing - WD-40 and slight pressure defeated the corrosion and the IF Bandswitch is now operational. After the WD-40 had time to seep into the bearing the switch operation is very easy and requires very little effort to effect band changes now.
4. Phone jack in IF-AF appears to be missing insulator spacer, wiring shot to jack. This appears to be an output from the detector. It must be for testing since access to this jack would be difficult if the receiver was installed into the cabinet. No access hole in the cabinet where the jack is located. This jack is for alignment and is for installing a detector plate current meter for measuring peak current during alignment. Though the bottom shields are missing, there was a hole in the shield to allow access to this jack.
5. Severe surface corrosion on all transformers and chokes (due to steel cases.) These components will need repainting after the corrosion is removed. Most of these components are actually bypass capacitors.
6. Generally, the Tuner and Power Supply are in better condition than IF-AF unit which has the most damage and will be the most difficult to restore to functionability.
The Tentative Restoration Plan - Though a restoration can usually be accomplished without a manual or schematic, it's much easier and ultimately much more complete and accurate with a manual for reference. The first step is to get some documentation (manual found.) During disassembly, all removed parts, including hardware, will be "bagged and tagged" in individual, identified plastic bags. This will be a tremendous help during reassembly since all parts will be easy to find and easy to identify. Since the Tuner and the PS are fairly heavy they will have to be restored in the shop. The PS will be restored first since it appears to be in the best overall condition. The Tuner will be restored next since it's better than the IF-AF unit. Both of these pieces can be worked on in the Summer out in the shop. The IF-AF unit is about 75 lbs out of the cabinet and can be brought into the upstairs lab for repair. This can be done during the Winter, if necessary. Cabinet repair will be done last after the RAA is operational and the Tuner, the IF-AF unit and the PS panels have been restored. If the cabinet restoration ends up being a Winter project, painting may be postponed until it warms up. One caveat,...this plan is subject to change depending on what unforeseen problems are encountered during the restoration process (and we do expect to find many more problems than those listed so far.)
Panel Dismounting -
July 1, 2017 - The first step in disassembly
is to dismount the front panels. This will allow easier moving
of the chassis of both the Tuner and IF-AF unit. Also, further
disassembly can then proceed with the panels off. But first, we
have to deal with stuck screws.
Stuck Screws - Even though the chassis and shields are brass and the screws are brass, both still oxidize. I'm finding that some of the screws will break the heads off rather than unscrew. I find that I have to soak the screws in penetrating oil overnight before trying to remove screws. If the screw is still stuck then I apply heat and more penetrating oil. The heat is applied with a soldering iron tip directly to the screw head. The heat-expansion "breaks" the corrosion and helps the oil penetrate which usually allows the screw to be removed without damage. After the screw is removed the threaded hole is "chased" with the proper size tap to clean out any remaining corrosion.
Knob Set Screws - The knob set screws are 8-32 spline socket set screws. None of my spline wrenches fit this spline socket correctly. I had to make a special tool that fit into the spline socket tightly to allow set screw removal. Again, corrosion of the steel set screw in the brass hub of the knob seems to be encountered in every knob and each knob has two set screws. Soaking in penetrating oil overnight is the first step. Then apply heat with a soldering iron tip directly to the set screw. I use a small soldering iron tip that will fit down the barrel to contact the set screw directly without touching the sides of the knob barrel. It helps to alternate between heating and then cooling with more penetrating oil followed by more heat. This procedure was successful for removing the set screws in all but two knobs. These knobs had set screws that defied all the normal removal techniques. Alternating heat and oil over a period of two days with special tools such as a reverse-twist drill and a screw extractor proved useless.
|Front Panel Removal
- July 5, 2017 - What was necessary to remove the final
two knobs may seem unthinkable but the two knobs had to be
destroyed in order to remove them from their shafts and allow
dismounting of the front panels. I had original replacements for
the knobs, so we weren't dealing with irreplaceable parts. I
used a Dremel tool and a "cut off" disk to first slice the
bakelite off of the brass hub. Once the bakelite was removed,
then I used the "cut off" disk to cut away just the set screws.
Once most of the set screw itself (two in each knob hub) was cut
away, the pressure is released and the hub just slides off the
shaft. If done carefully, no damage will happen to the shaft.
With the knobs removed, the next step was to remove the remaining panel screws. Four of the panel screws on the Tuner had been broken sometime in the past. I applied penetrating oil for about two days before trying to remove the remaining screws. I used a blade screw driver that was a very tight fit into the screw slot. Once the blade was in place, I gave the screw driver a couple of hits on the handle to transfer the shock thru the screw. All of the remaining panel screws were removed successfully using this method.
The Tuner panel has some serious erosion on the back where the vertical mounting brackets were attached. In order for the vertical mounting brackets to be fully "flush" against the back of the panel, the erosion will have to be filled. Since the panel is going to be reconditioned to remove oxidation and prepared for painting, it should be relatively easy to use real metal body filler to fill-in the eroded areas. This can then be sanded flat. How it matches the undamaged aluminum remains to be seen when we actually go thru this process.
The IF-AF Unit panel was in good condition although dirty and a bit of surface oxidation. All removed hardware, knobs, tags, handles, tubes, etc. were "bagged and tagged" in plastic bags for easy identification for the reassembly process.
|photo left: Tuner with front panel removed. Note the
decade tuning dial gear that is driven by the tuning shaft. Note
how clean some of the coil boxes are. These were inaccessible to
mice and contaminates.
photo right: The IF-AF unit with front panel removed. Although this looks pretty bad, the rust is mostly surface corrosion. Note the foremost bypass condenser has been cleaned just using a brass brush.
Supply Panel Removal - July 9, 2017 - Overall
there is much less corrosion on the Power Supply. The cabinet
and panel had fully screened ventilation holes that prevented
any entry of mice or other damaging pests. Inside the chassis
is fairly clean and the components appear in good condition with
little or no rust anywhere. Underneath the chassis is about the
I applied penetrating oil on all panel mounting screws and nuts the day before I attempted unscrewing any hardware. This helped a great deal as nearly all screws were easily removed. Only the cable clamp screws proved somewhat difficult but eventually they were removed undamaged.
The photo to the right shows the power supply with the front panel removed. The rust spot on one of the filter capacitors appears to have been caused by moisture trapped by the cloth woven cover of the wiring harness.
Continuity Tests and ACV Tests -
July 13, 2017 - The first step
to determine if the power supply is going to function is a continuity
test of the iron,...that would be the power transformer and the two
chokes. Next would be to test the oil-paper filter capacitors for shorts
and value. Since we have the rectifier tubes removed, we can actually
apply AC voltage to the primary of the power transformer to test its
functionability. Since no DC high voltage can be developed, we are only
checking the primary, the filament voltage windings, the high voltage
winding and the AVC AC voltage winding. If these tests show the
transformer produces the correct AC voltages, then it will be left
powered for about 15 minutes to see if any heat develops. Without a
load, the transformer should stay cool.
Test Results - All iron checked good for continuity. Capacitors checked as "not shorted." There are three vitreous enamel coated, 100W tapped resistors. All three resistors have open sections and therefore have to be rebuilt. These resistors makeup the voltage dividers that provide the proper B+ and negative bias voltages. The AC power cable has to be replaced. This was a shielded cable originally but the cable inside the shield is rotted. The AC power switch tested okay. Someone installed 20A fuses, should be 5A. The AC power switch and fuse block assembly needs partial rewiring that is mainly due to rotting of the AC power cable within the assembly. Replacing the AC power cable will correct the majority of the problems. I haven't tested the coils and capacitors within the AC Line Filter unit yet.
|What Needs Rework on the
Power Unit - The three vitreous enamel coated resistors
need rebuilding. New AC power cable. Rebuild output wiring harness.
July 15, 2017 - Cleaned and reconditioned the AC power switch, fuse board, power cable input and output box. Removed shield from old cable which is soldered to a metal tube that projects out the side of the unit and side of the box. Original wire appears to be 14 or 16 awg 2 conductor with black rubber jacket with shield sleeved over the cable.
July 16, 2017 - Clip-lead connected 120vac to thru the AC line filter to the power transformer. HV winding was over 400-0-400vac. Tube heater winding was 3.0vac. AVC voltage winding was 3.0vac. Rectifier heater was 5.9vac. Voltages were somewhat high because the AC line voltage was 120vac and also there was no load on the windings. Let AC voltage remain on power transformer for about 5 minutes with no changes in voltages and no heat build-up.
July 17, 2017 - I found it was difficult to locate any "new" 14-2 power cable at local stores. However, Home Depot in Carson City did have the correct type cable in stock. Lowe's and True Value don't carry 14-2 anymore and it is difficult to find online except by the 250' roll. I think two-conductor power cable is not going to be an in-stock item much longer.
|July 19, 2017 -
Miscellaneous Mechanical Work - Removed all broken 10-24 screws
that had been used to mount the front panel of the Tuner to the chassis.
There were six screw ends that needed to be removed. I had been putting
penetrating oil on the screw ends for a few days. The first screw end
was long enough that it could be grasped with vice grips and unscrewed.
One other screw was just barely long enough to grasp and remove. The
next screw had to be drilled and a screw extractor used to remove it.
The remaining three were drilled and threaded themselves thru and out as
the drill bit grabbed while cutting. When all broken screw ends were
removed, I used a 10-24 tap to chase the threads to remove any
corrosion. The IF-AF unit didn't have any broken screws but the threaded
holes were chased to clean-up the threads and remove any corrosion.
Power Supply - Soldered the original RCA spade lugs to the new AC power cable. This cable connects to the fuse board terminal strip using these two spade lugs. The fuse board also has to output lugs that have to be soldered to the AC Line Filter input wires. I'm going to install new shielding over the new AC power cable. The original was copper braided shield that looked exactly like the shield used on RG-8 coaxial cable, so that's what I'm going to use. The original power cable was about three feet long. Probably when onboard ship the receiver/power supply was connected directly into a wiring box and didn't use a "plug" and the cable was probably just long enough for the connection. I'm going to have a six foot power cable with the braided shield (from RG-8) over it. The original shield was soldered to the AC input metal barrel for the AC cable input to secure that end. The plug-end had the shield secured using a tightly wrapped length of TC that was soldered. This kept the shield in place if the power cable was moved. I'll secure the shield in the same manner but it will have an early-style, heavy-duty two-wire 115vac plug for connecting the power. I'm considering running the PS using a 1:1 isolation transformer with separate ground for the RAA chassis. This would replicate the "floating" AC that was used onboard ships. Another advantage of the isolation transformer can be adjustment of the actual AC voltage applied to the receiver since our house line runs over 120vac.
|Stripping - July 21, 2017
- I had to do some methylene-chloride* stripping on another
project, so I though I'd subject the IF-AF Amplifier panel to the
stripper and see what happened. The remaining paint on this panel was so
oxidized, it just about fell off when the methylene-chloride hit it.
With the paint off, I can see the pitting and corrosion that has
occurred on this panel. It's not bad and will clean up with just a
little scrapping and application of abrasives.
Missing Hardware - While trying the stripper, I also removed and "bagged and tagged" all of the knurled thumbscrews on all three panels. I noticed that the Power Unit and the IF-AF Amplifier panels were complete with all of their thumbscrews but the Tuner was missing three long thumbscrews and one short thumbscrew. I'll have these replicated, probably by one of my machinist friends. They are black finished brass and use a C-clip to retain the thumbscrew to the panel.
Also removed the screens from the Power Unit front panel in preparation for stripping and painting. Since the Power Unit is in good condition, I'll paint this panel now to allow the Black Wrinkle Finish plenty of time to harden. It usually takes minimum two or three days for wrinkle finish to get hard enough to remount parts. Waiting a week is better. Maximum hardness of the wrinkle finish usually takes about 30 days to cure.
July 22, 2017 - Stripped the Power Unit panel. It turned out very nice. Had to do a light sanding with 220 grit to remove the very minor oxidation pits. Once the panel is wrinkle finish painted none of these minor defects will show. See photo below upper photo.
Tried NaOH (Easy Off Oven Cleaner) to remove the green oxidation on the side of the Tuner chassis. This worked fairly well. Required two applications to remove about 80%. Probably one more application will remove the 20% remaining. As far as dirt, oil, grease or any other contaminate, these were gone with the first application.
*Methylene-chloride stripper is very hazardous and must be used OUTSIDE only. Do not use this type of stripper in an enclosed, non-ventilated area. All types of commonly found gloves DO NOT protect your hands. You must use PVA gloves that are layered.
|July 23, 2017 - Power
Unit - Moved AC input from 115vac tap to 120vac tap. Rechecked
the voltages at the power transformer. HV was 415-0-415vac, HTR was
2.9vac, RECT FIL was 5.5vac, AVC FIL was 2.8vac. Again, this is with no
load. The circuit normally has a 1144 ohm 100 watt resistor that is a
constant, "dead" load on the
B+, so I'm sure once everything is up an running the voltages will be
much lower and probably in spec.
Calculated all wire wound resistor dissipations and designed replacements for the three open WW 100W resistors. These replacements will "plug in" to the mounting clips as the original resistors did. Unfortunately, it's impossible to repair the original resistors and the only acceptable method is to design and build replicas that fit into the original clips and provide the same resistance and dissipation. The replicas will have terminals for mounting individual WW resistors and will be built on a strip of high-temp delrin. Though they won't look like the originals, they will fit exactly and operate correctly. The original WW resistors will be saved for future reference.
IF-AF Amplifier - Panel oxidation was cleaned up using 220 grit sand paper. Some of the oxidation/corrosion areas are pretty rough and may require further treatment and perhaps minor metal filling. The oxidation/erosion of the metal may be due to dissimilar-metals with salt residue and moisture acting as an electrolyte. The erosion is only where there was contact of the aluminum with nickel-plated brass parts such as the chassis vertical brackets used in the Tuner or the contact of the aluminum panels and the nickel-brass cabinets.
Had to drill out two broken 4-40 screws on the IF-AF panel. Chased all 4-40 threaded holes with a tap to clean threads of any oxidation. IF-AF Panel photo lower right.
|Tuner Panel Backside - The
photo to the right shows the severe erosion that is located on the back
of the Tuner panel at the upper left part of the panel. As can be seen
by referencing the straight-edge, the erosion in some areas is almost
halfway thru the panel thickness. As mentioned above, this erosion is
not everywhere. It is only where the nickel-plated brass made contact.
Some areas are very minor and clean up with 220 grit sand paper. The
area shown in the photo is the most serious. Some of the residue found
when dismounting the front panels appeared very similar to "baking soda"
which makes me think that maybe it's salt residue from "salt-air" of the sea
that was "trapped" over the years and then had time to react with the
moisture of the storage environment. Salt water can be very corrosive. Well, regardless of what caused it,
the question is how to repair the damage?
After a thorough cleaning, I'm going to try using USC All Metal Aluminum body filler. It is a catalyst-activated paste filler used in autobody repairwork. It should be strong enough and if the area is ultra-clean, it should adhere quite well. When it sets up, it can be sanded to be flat with the non-damaged surface. Since the non-damaged aluminum will also be sanded and the all metal filler is also aluminum silver in color, hopefully the repairs won't be too conspicuous.
As mentioned somewhere further up this page, the back of the Tuner panel has to be fairly flat so the mounting against the two vertical support brackets aren't distorted or bent when the mounting screws and nuts are tightened.
|July 27, 2017 - Tuner
Panel Work - Three broken screws had to be drilled out. 4-40 tap used
to chase threads afterward. On all three panels, all broken screws have
been removed and all threaded holes are now open with the correct
threads. Stripped Tuner Panel of all remaining paint using methylene-chloride. Wet sanded panel
back and front to assess condition. Front of panel is very good with
only a few corrosion spots that aren't serious. Rear of the panel is in good
condition except the upper left area (viewed from rear of panel.) Wire
brushed corroded area and it cleans up but will require a heavy-duty
rotating steel wire brush to remove all corrosion and residue. I'm going
to use USC All Metal Aluminum Body Filler to "level" the rear side of
the Tuner panel.
Power Unit - Replica Wire Wound Resistors - Checked Mouser and all resistors required are in stock. Order soon. Checked measurements of 1" copper pipe end caps to use for end caps on replica resistors. These are virtually the same diameter and will work perfectly. Bought six caps to build the three WW resistors needed. Test fit into mounting clips and the fit is perfect.
July 29, 2017 - Ground post was causing some interference with thorough cleaning of the Tuner Panel. This post was a "press-fit" with serrations to prevent it turning. On the back side, a 10-24 screw and internal-tooth lock washer also secured this ground post to the panel. Used a large socket to act as an anvil with a clearance hole for the ground post. With a 10-24 threaded into the post, I tapped the post out of the panel with a small hammer hitting the top of the screw. No damage to either the ground post or the panel. Ground post and screw were put into the "Antenna and Ground Post" plastic bag and the bag placed in the box with the other bagged Tuner parts.
Photo right shows the Tuner panel totally stripped of paint and hardware. The panel is setting in front of the Tuner chassis to see how everything fits.
|Aug 3, 2017 -
Made it to Sparks, Nevada and to Summit Racing to purchase a quart of
USC All-Metal Body Filler, which they had in-stock. Also, purchased
three cans of VHT Black Wrinkle Finish for painting the Power Unit panel
and the AF/IF panel. Tuner panel will be painted after the body filler
has successfully repaired backside of that panel.
Delay in our restoration work is due to re-laying out the shop to have more shelving for storage and moving an eight-foot work bench to a better location that allows more work space and an "in shop" test and repair bench with full lab equipment. A couple of weeks delay will end up with a much easier environment to work in.
To be continued,...restoration updates every week or two
1. Model RAA Radio Receiving Equipment - Manual, RCA Victor Company - June 30, 1931 - The manual provides detailed information on design, construction and operation. Schematic, wiring diagrams, parts list, alignment instructions.
1. www.navy-radio.com - Nick England's incredible website provides a wealth of information on all aspects of Navy Radio. Photos of the RAA-2 onboard the USS Texas and the 1941 USS North Carolina Radio Room No. 2 were provided courtesy of Nick England. Many, many vintage photos. An excellent resource for those interested in Navy Radio gear, stations and history.
2. Training Film from Navy Department - Radioman Training, 1943 - This 10 minute film covers how Navy orders that originated in Washington D.C. were transmitted by NSS and then relayed to NPG and then to NPM where it was then relayed to ships in the Pacific. Lots of WWII radio gear shown in the film.
3. Wikipedia and other online sources - Info on Destroyer Tenders USS Whitney and USS Dixie. Repair Ship USS Medusa.
Thanks to: Bob Welch W6AQU, Robert Goff W7MKA, Chuck Cusick KØDWC, Joe Conner, Steve Rosenfeld, Rob Flory and Nick England for their help and information.
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