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Auburn/Cord A1414 bad local osc coil... - Printable Version

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Auburn/Cord A1414 bad local osc coil... - 37-Cord - 12-21-2025

Well, I figure to make my first post here a doozy (pun intended). 

My father-in-law owns a 1937 Cord, and I'm trying to get the radio working. I have a lot of background in electronics and tube electronics.

I couldn't find any diagrams of the A1414 Philco chassis (A for Auburn). But it is very similar with only slight differences to the R-1415 Reo and W-1419 Willys radio depicted in Rider volume 8, and similar also to Packard P-1417. 

I got the power supply sorted with a solid-state vibrator, buffer cap and a couple of other caps. Nice clean 195v. 

Started working my way back through the stages, audio-out, 1st audio, IF, and eventually figured out the local oscillator wasn't working. 

Checked the coil and it was not reading any thing on the primary (g2) winding. Took it out and the small, outer winding was open, and the larger inner winding was reading high ohms. Did a little soldering and was able to get the outer winding reconnected, but the coil is still bad reading high ohms on the secondary. Just a few winds of "green rot" visible under the wax, but mostly intact otherwise. But that's that.

So I need to either find a local-oscillator coil or re-wind it.  The Philco number is 32-2496. Doubt I'll find a friendly neighborhood Philco factory store in the neighborhood with spares on hand. 

In the mean time, used the signal generator and scope to inject RF at the antenna input and verify it is is tuning and passing that up to the 6A7, then nothing since there's no local osc. So I injected 260kc signal and it seems to be passing that all the way to the detector. IF seems pretty close, peaking at 258kc, just shy of the target 260kc. 

So I think the bones are good. Some evidence of prior repair as one of the bakelite capacitors has been bypassed. But nothing looks molested. 

The car is beautiful and a show winner. Would be really nice to get this original radio working. 

Suggestions on sourcing the coil, or tips on re-winding it appreciated.

RE: Auburn/Cord A1414 bad local osc coil... - morzh - 12-21-2025

37-Cord

Welcome.

Have you fully recapped the radio? I suggest you do this before proceeding.

RE: Auburn/Cord A1414 bad local osc coil... - MrFixr55 - 12-21-2025

Welcome 37 Cord!

The The basic schematics for car vs home 6tube superhets are rather similar. The problem is that most home radios (popular) have IFs around 455 KHz (common) and most 1937 model Philco car radios (rare) have lower IF frequencies, so scavenging one from a home radio will be difficult. If this winding has many turns and you can reach the green rot area and can find the break, removing a few turns will change the resonant frequency of the coil but not beyond the range of the "padding" condenser adjustment. If the winding that you repaired (Some would refer to this as the tickler, as it connects via capacitor to the "grid plate" of the oscillator section of the tube) is only a single winding, it can be removed, counting the number of turns as you remove it, getting to the lower layer, repairing the layer, then rewinding the tickler. (What you referred toas the "screen grid" is actually the plate of the oscillator. This is often referred to as a "plate grid".).

By 1935 or so, the basic circuit of an AM Broadcast band radio was fairly standardized with the only difference being the presence or absence of an RF amplifier and the style of tubes used (large pin vs octal, vs Loctal vs miniature) and heater voltages.

The 6A7 (or 2A7 or 6SA7) is a common "pentagrid" converter and the circuit is rather common across manufacturers. 455-470 is a common IF frequency. However, newer radios have oscillator sections of the tuning condenser that have much less total area than the tuning capacitors used in older car and home radios that tended to be the same area as the RF section. Therefore, with the correct capacitor in series with the coil, it may be possible to get an oscillator coil from a modern (1950s) AA5 radio to work in this set. Most tuning caps have a capacity from 10pF (full open) to 365 pF (full mesh). For your set, the oscillator is tuned to a frequency 260 KHz higher than the frequency of the station tuned. The heterodyning of these 2 signals gives you a signal of 260 KHz, amplified by the IF stage. Don't ask me the value of capacitor needed to make this coil oscillate at 260KHz. There are HAMs and EEs on this site or you may be able to figure the calculation based on the value of the tuning cap, the inductance of the oscillator coil, the value of the cap in series with the oscillator coil, etc.

Good luck with the radio, please post a pic of it and of the Cord; it in itself is a technological marvel.

RE: Auburn/Cord A1414 bad local osc coil... - 37-Cord - 12-22-2025

I'm very familiar with vacuum tube electronics, as I've been repairing and restoring guitar amplifiers and tube hifi equipment for a few decades now. I'm old enough to have worked in a TV shop when there were still TV's getting repaired with tubes in them.

I did find the schematics and component layouts in Rider that I mentioned, with the REO and Wiley's chassis from the same year being quite similar. I've got one more bakelite capacitor in the A-1414 than those have, and the low frequency padder is moved to a different spot to accommodate the extra. I haven't traced it out, but at first glance I think it goes to the tone switch.

At the moment, I'm stuck on the oscillator transformer, which was definitely open on the "plate/grid" terminal that connects through the 250pf capacitor. The other two legs of the transformer are reading erratically around 750k-1M, which ain't good either. I was able to reconnect that one leg, since the outer coil end lead was easy to pull up from the wax and connect. But the other end of the outer coil (tickler?) connects to the inner coil somewhere under the wax I haven't gotten to yet.

I do have a spool of 38 AWG magnet wire that should work fine for re-winding. The original wire seems about the same except it has cotton insulation.

I'll poke around the transformer coil a bit under the microscope and see if I can get the wires reconnected. Otherwise, I'll document the direction and number of turns of the outer coil, peel it off, and see if the inner coil can be salvaged in place.

I'd guess there's maybe 20-ish winds of the outer coil, which with a little patience, could be hand wound. I'll need to build winding tool of some sort if the inner coil has to be re-wind. Eyeballing it, and watching a youtube of someone else re-winding a similar coil from an AC powered radio, I'd guess it is about 100 turns, neatly wound.

On the re-capping suggestion, I'll consider it, but knowing the oscillator transformer is totally kaput, not much point in proceeding with that until that's fixed.

RE: Auburn/Cord A1414 bad local osc coil... - RodB - 12-22-2025

Just a little heat from a heat gun will melt the wax. Be sure to collect it so you can cover up your mistakes on the rewind. :-0 Hah

RE: Auburn/Cord A1414 bad local osc coil... - MrFixr55 - 12-23-2025

Hi 37 Cord,

The Philco library has documents on rewinding oscillator coils, but they are for rather large forms (3/4-7/8 in.). Early Philco coils were notorious for failure due to a reaction between breaking down insulators causing an acid reaction that ate through the wiring. The newer wax impregnated ones usually do not have this issue, but I do have an open IF transformer on a 1940 Mantola portable that I will eventually get to. The open is at the bottom of the coil, of course.

When I rewound the Philco coils, I would tape a piece of thick paper as a "dam" for lack of a better word. I would push the coil against this dam while winding and would get a neat coil that way. Thin Litz wire is not readily available but if this coil is indeed the tickler, the spacing provided by the cotton covering is likely not important.

Unfortunately, Philco, like many manufacturers, did not list the inductance, turns ratio, or other specs for the coil and certainly did not list parts from aftermarket suppliers, such as Meissner, Thordarson, etc.
Sams Photofact (Howard Sams, Inc.) did list replacement part numbers from suppliers to the radio repair trade, but I don't know if they documented this radio (they did have a car radio series).

Worst case scenario, I hope that an oscillator coil from a more modern radio may be made to work.

Your experience and talent are very much appreciated here! Do find the time to explore our Phorum as there are forums in our site for Audio, especially tube HiFi amps. Our late founder, Ron Ramirez was a fan of the Fisher sets from the late 1950s. One of our members, TV Man is in the process of building some Chinese kit "monoblocks that he is modifying the design of for better performance. Also check out "Old Ron's Bar and Grill" get a virtual burger and brew and shoot the breeze about the weather, what you fixed recently, etc.

My brother is a bassist who has an Ampeg B15 that I have repaired. I have a Premier (supposedly an 88 but it does not match the schematic). I found it at the curb about 50 years ago. It appears to be built with loctal tubes including 4 7B5s which are the equivalents to 6K6, and what appears to be government surplus capacitors from ARC5 aircraft receivers and even a few "dog bone" resistors. The styling of the amp appears to be more 1940s than when it may have actually been made. The amp case is a clamshell where the speaker is separated from the amp when in use. The speaker is a Jensen, but with an electromagnet, powered by its own supply instead of being used as a choke in the amp's power supply. It appears to be a professional unit, but not from the "Rock" era, maybe from the "Big Band" era. I will get around to it eventually. If you ever heard of or saw one of these, I would love to get any info that you have.

RE: Auburn/Cord A1414 bad local osc coil... - 37-Cord - 12-23-2025

Thanks!

I have done a lot of audio restorations. Long ago, the side gig was buying up estate sale tube hifi, fixing it up and selling it. I've had lots of coveted tube hifi equipment for a little while anyway.

Most of my tinkering the last 20 years or so is guitar amps, repairs, restorations and some home-brews.

I've not gone down the antique radio path. I understand how it works, just not as familiar with it.

I've seen a youtube of someone re-winding what I think is a table-radio oscillator coil. It looks very similar to what I have in hand here.

Good point on the litz wire. I only found one conductor in the end of the coil wire, along with cotton. Didn't occur to me that it might be litz, since I only found the one conductor.

The outer coil is easy to see. The inner coil, which is reading crazy high resistance (around a megohm), is more buried in wax, and I can't make out what it is made of or how many wraps there are.

I've always been told this wax is beeswax, I don't know if it is or isn't. I did look around and found USP (pharmacy grade) beeswax prill (little balls), yellow or white.


It would be great to figure out the values of the coil before I take it further apart. From signal injection, I can tell the I.F. is 260kc, and the RF amp is functional and tuning properly. I can probably work backwards from there, perhaps measuring the tuning capacitor and trimmers (padders) and doing some calculations.

The particular oscillator transformer I have is a 3/4" diameter phenolic air-core. Looks like there might be a thin outer sleeve that the outer (tickler?) coil is wound on.

I'll try to get some photos of it and maybe from the microscope too.

RE: Auburn/Cord A1414 bad local osc coil... - MrFixr55 - 12-24-2025

Hi 37 Cord,

That would help.

Yeah, I doubt that any part of the oscillator coil should be in the megohm range. most windings in oscillator coils read under 25 ohms or sometimes less than 5 ohms. I am hoping that the break i at the "top" of the winding, right under the tickler.

The wax can be melted off the coil by heat gun (be careful) or in an oven set no higher than about 200 degrees (be careful that the Wife is not home, of course).

if the break is found and is not under the tickler, it can be spliced. In fact, there are supposedly instances that this occurred in production during the early 1930s. When the spool ran out in the middle of winding, they merely spliced the beginning of the next spool to the unfinished coil and finished the winding. However, each winding was a single layer back then, as the coils were rather large.

Attached is a You Tube video of troubleshooting an oscillator coil on a Philco 37-600 radio:
https://www.youtube.com/watch?v=cFka3_i_Dss&t=7s

Does your coil look similar or does the tuned potion of the coil look more like a tire?

RE: Auburn/Cord A1414 bad local osc coil... - 37-Cord - 12-24-2025

A lot closer to this video:

https://www.youtube.com/watch?v=hzkMEfP2yLE

I've also seen that winder he's using on Amazon for under $40, so thinking about it.


Picture of the underside, oscillator coil pointed to by the yellow arrow. This is how the chassis was when I first opened it. 

   

RE: Auburn/Cord A1414 bad local osc coil... - 37-Cord - 12-26-2025

Happily, I was able to repair the coil last night. Found a second break in the primary coil.

Then I began probing the secondary coil by moving some of the wax out of the way and scraping the enamel (or varnish, whatever they used) from the wire and testing for continuity. Found the winding right above the end of the secondary coil was open, but the winding right above was still good. Decided to just bridge the windings with a dab of solder and that got a decent 14 ohm resistance.

I think I only lost maybe a half-a-turn in the secondary coil, but was really happy the defect was above the primary coil layer. 

Applied an 800khz signal to the primary and put the scope on the secondary and it was working nicely and stepping up the input about 2.5-3x.

Once tested, I redistributed some of the excess wax to where I did the repairs, and gently heated with a small heat gun to soften and just melt the wax. Sealed my work up and immobilized it.  

It is in the radio now, the radio is tuning stations with only 3-foot long wire clipped onto the antenna input.

Still need to go through the rest of the radio, but it is working pretty well now. 

   

   

   

   

RE: Auburn/Cord A1414 bad local osc coil... - Arran - 12-28-2025

Hopefully the repair holds, I don't think leaving out a few inches of wire will make that much difference, if the dial tracks properly it obviously was within the tolerance of the padders and trimmers.
Regards
Arran

RE: Auburn/Cord A1414 bad local osc coil... - MrFixr55 - 12-28-2025

Congrats!! Post a pic of the completed radio and a few pix of the Cord, especially the interior and the engine! very unique car. Of the entire Auburn Cord Duesenberg company, I think that only Lycoming still exists, now owned by a different company. At one time, ACD also owned Checker. The company had a "Checkered" past (pardon the pun) as E.L Cord, Auburn Cord Duesenberg and Checker ran afoul of the Securities Exchange Commission over stock deals and antitrust issues. Production of Cords ceased in 1937. Cord was a pioneer of front wheel drive with the L-29 in 1929. The Cord 810 and 812 used a 289 CID Lycoming V8 (supercharged in the 812). The "coffin-nosed" body was designed by Gordon Buehrig who was also responsible for the Auburn 851 "Boattail" Speedster and the Duesenberg Model J, and later on, the 1955 and 1956 Lincoln Mark II.

RE: Auburn/Cord A1414 bad local osc coil... - 37-Cord - 01-05-2026

With all the rain we've had lately, I haven't had a chance to take more pix of the car. It is really clean, and the Lycoming V8 purrs like a kitty-kat.

Father in law got the radio back in the car and I trying to figure out how to get the on/off switch and the volume controls to line up. 

Working great, all I needed to do after the repair was tweek the local oscillator trimmer caps a little since mucking with the transformer disturbed the resonance a little bit. 

   

RE: Auburn/Cord A1414 bad local osc coil... - morzh - 01-05-2026

One needs a Cord to plug in a radio.

RE: Auburn/Cord A1414 bad local osc coil... - MrFixr55 - 01-14-2026

Never saw one of these from a side view, the "beauty shot was almost always from the font. The "coffin nose" and hidden headlights in the fenders are totally iconic!