Silvertone 7085 Wire Recorder

The Silvertone 7085 is a combination radio, phonograph, and wire recorder.  It is circa 1947 and is the cabinet or table top model (there is also a console model).  It has eight tubes.  It can be a normal radio or 78RPM record player.  It can both play and record on recording wire from the radio, phonograph, or from an included microphone.  The radio is nothing special - basically an AA5 using Loctal tubes.  It has a built in loop antenna, and will also accept an external antenna.  The three additional tubes are used for the wire playback head preamp, the recording bias oscillator, and a second rectifier tubes.

The radio had seen minimal servicing in the past - most of the original parts were still in place - only two small capacitors had been replaced.  

The schematic for the Silvertone 7085 (chassis 101.814) can be found on Nostalgia Air (under model 8085).

My antique radio restoration logs

Condition As Found

This unit was purchased on eBay.  Even though they are large and complex, they do not go for much money.  Unrestored units typically run $60 to $100, but of course are expensive to correctly ship!  My unit was complete with all knobs and the back cover/loop antenna. Two spools of recording wire were included (used - interesting to see what was recorded!).  The original microphone and its base was present.  The phonograph cartridge and needle was present, but crystal cartridges last only a few years and thus it was assumed to be bad.

The unit had been invaded by mice at some point in its past judging from the existence of nesting materials (newspaper).  They had chewed some wires and cables, but mostly the cloth sheaths on the phonograph pickup lead and transfer switch cables.  The chassis had some rust or corrosion due to their urine, and the speaker frame was severely corroded!  As found, the motor would run, but the none of the rotating parts functioned.  I assumed this was due to caked-on lubrication and/or bad idler wheels.  The cabinet was in presentable condition, but appeared to have suffered some water damage in the past (two stains and finish loss on the bottom front corners.  I did not test the radio, since I do not normally apply power until the radio has been examined, tubes tested, and capacitors replaced.

Previous Repairs

Two small capacitors had been replaced.  All the rest looked original.  Not all tubes were Silvertone brand, so I assumed that some had been replaced.


My usual restoration procedure is to first make a complete survey of the condition of all components.  The survey results guide my restoration strategy.  If major and unique components are defective or missing and cannot be restored or replaced, I may elect to sell the item rather than restore it.  I always assume that all paper and electrolytic capacitors are leaky and thus should be replaced.  


Before starting restoration, I had to make sure that the phonograph/wire recorder transport mechanism could be made to work at reasonable cost.  At least the motor ran, but the turntable (which doubles as the wire take-up reel)  and wire supply reel did not turn when the function switch was moved.  I initially assumed that this was due to caked-up lubrication and/or bad rubber tire idler wheels (it had THREE idler wheels).  After some disassembly, I found that a torsion spring was missing in the mechanism.  This spring (part 49 in the diagram below) links the function switch to a lever that shifts the idler wheels from the turntable (play mode) to the supply reel (rewind mode).  I made several attempts to reproduce this part from my collection of springs.  After several attempts, I made one that "sort of" worked.  The turntable would rotate and pull wire from the supply reel in PLAY mode, but there was not enough torque on the take-up reel in REWIND mode.  At this point I was convinced that I would have to find a replacement spring.

I picked up an old Crescent Model H-22A1 wire recorder a the Charlotte AWA Conference (it was in the free pile, since its case had been eaten by termites!). I was hoping that it would supply the missing spring.  But alas, even though the mechanism looked identical to my Silvertone from the top, this unit was push button/solenoid operated, and it did not have the missing spring.  I also contacted a seller on eBay who restores and sells wire recorders.  He told me that this particular spring is often missing or broken in the units he restores.  He makes up his own springs, a complex process involving heat treatment afterward.  I could have purchased a complete mechanism from him, but the cost would have been double what I paid for my entire unit, and the mechanism was a different part number and designed for a different radio chassis.  He did supply me with a parts list for the Silvertone, so I would at least learn what the spring looked like. I next contacted West-Tech Services, who repairs these units, and asked if they could supply the part.  They were able to come up with the missing spring.  But it was very expensive ($50 with shipping) likely due to the cost of labor to disassemble a unit.  And to make matters worse, the spring they supplied was not original - it did not work any better than my reproduction.  I assumed that since the spring supplied by West-Tech Services was removed from a working unit, there must be something else wrong with my mechanism.

I found that with my spring installed, the turntable/take-up spool worked as it should.  But in rewind mode, the supply wheel did not provide enough torque.  Since the idler shifter was apparently working properly, I now began to suspect the idler wheel that drives the supply reel.  Just like with phonographs, the rubber tire will harden with age and begin slipping.  I then again looked at the parts in my junker Crescent wire recorder.  But the pulley (part 73) and lever (part 66) were ever so slightly different than the corresponding parts in the Silvertone, and the bushing was too small to fit over the corresponding stud.  But the idler wheel in the Crescent was in excellent condition.  With nothing to lose, I enlarged the hole in the lever (part 66) so that it would fit over the stud in my unit.  I did this using a series of drill bits in my drill press, and finished using a small round file.  Once this idler and lever was installed, the mechanism worked properly in all modes, and would properly rewind a reel of wire.  Of course, at this point I did not know if it ran at the correct speed.  But now that the mechanism could be repaired, I proceeded with the remainder of the restoration.  The transport mechanism was then completely disassembled and all parts cleaned and lubricated before reassembly.

At this point I made BEFORE photos of the radio chassis top and bottom.  I use these photos to ensure that replacement parts and wiring are placed as close as possible to their original position.  Some radios are subject to problems (such as oscillation) if wiring is re-routed or lead dress is not the same as the original..

The top and sides of the chassis were cleaned with GoJo hand cleaner and 00 steel wool.  Since this process may leave small steel wool fragments that can cause problems later, I follow up with a thorough vacuuming and go over everything with a small magnet and masking tape to pick up any stray fragments.

The power switch on the tone control was flooded with Big Bath cleaner/degreaser through a small opening in the control.  After the switch was cycled many times, it worked well.  The sticking spring-loaded slide switch which was part of the function switch assembly was removed, disassembled, cleaned and lubricated.  While apart, the contacts were also cleaned.  After reassembly, it still did not operate reliably - still sticking.  I determined that the return spring was not providing enough tension.  It was stretched slightly and reassembled.  After this, the switch worked as it should.

All 26 paper-wax capacitors in the radio chassis were replaced using modern 630 volt axial film capacitors.  I chose not to restuff the original capacitors in this unit, since it is not a particularly valuable item, and about half the capacitors were Sealtite solid wax caps that cannot be restuffed.  The 10 out-of-tolerance resistors were replaced from my stock of NOS carbon composition and film resistors.  One 25 ohm 1 watt wire wound resistor (surge limiter from the cathode of one of the rectifiers) was open.  I replaced it with a 22 ohm 1 watt carbon resistor.  The radio chassis has two can type metal twist lock capacitors.  Both were rebuilt in their original cans, and the original terminals retained.  This way, the original wire and component routing could be used.  There is hardly any room under the chassis to install terminal strips and new tubular electrolytics.  The 40+40mfd@200 volt unit was rebuilt using 47mfd@250 volt radial capacitors.  The 40+40@150, 20mfd@25 volt unit was rebuilt using two 47mfd@160 volt radial capacitors and a 22mfd@50 volt capacitor.  Both units had cardboard sleeves which were replaced (but not glued, in case they need to be removed later for servicing).  My restuffing process for twist lock capacitors is as follows:

Several wires that had been chewed by mice were replaced.  The volume control and tone control were each given a shot of Big Bath cleaner and cycled.  The function switch was also cleaned using Big Bath spray and operated repeatedly.  Two used/tested 35Y4 tubes were installed.  The remainder of the tubes were good and were reinstalled after cleaning.

I decided that I could not live with the rusty speaker, even though it apparently worked OK.  My junker Crescent wire recorder used a similar speaker.  It was the same diameter and voice coil impedance and the mounting holes were the same.  But it had an output transformer riveted to the frame.  The original speaker had a 3-pin plug installed which mated with the speaker cable from the chassis.  I drilled out the rivets and removed the transformer.  I then moved the original speaker plug to the replacement speaker.  The original speaker cable had been chewed by mice, and had to be replaced anyway.


The cabinet was thoroughly vacuumed and then cleaned with GoJo hand cleaner and steel wool.

Testing and Alignment

Once the radio chassis was reassembled and the tubes installed, power was brought up slowly using a variac.  AC power consumption was monitored using a watt meter, and a DVM monitored the two B+ sources.  The radio worked immediately.  The radio was then aligned.  The performance is nothing to brag about - it is really just a normal AA5 circuit using Loctal tubes and an unshielded loop antenna. 

The wire recorder function was first tested using the used reels that came with the machine.  It was found that playback worked well, and it appeared that the unit was operating at the correct speed.  One recording was excerpts from Handel's "Messiah" recorded from a radio broadcast, probably in the 1950's.  I then attempted to record from the radio to the reel.  That function ALSO worked!  I was not able to test recording from the microphone, since the microphone was dead.  And the phono cartridge was also dead.  At this writing, I have not decided to restore these units, as the cost is considerable. West-Tech Services charges $60 to restore a crystal microphone, however replacement elements are often available on eBay for as little as $10.  However, these may not fit in the microphone case without modifications.  West-Tech also sells replacements for the Astatic L-71-A crystal cartridge and stylus, as do other companies on the Web.

There is considerable information on wire recorders on the web.  I found several interesting sites:

Operating Instructions
Great information and lots of additional Wire Recorder links
Video Exchange Transfer Service - Transfer service from wire recording to CD and other media.

Restoration Results

Chassis After Restoration