[NostalgiaRadioTime]

Lucky me, I need to rewind not only the Oscillator coil on my 1935 model 89, code 123, but also the RF coil. I've read through all of the coil rewinding information I could find here, but I'm wondering if anyone who has done this before saved their notes and could be kind enough to share? Mostly I'm trying to find which ends of the coil wires go to which terminals on each? It appears as if on the OSC coil that the infamous "tickler" winding is on the inner coil? Having never done this before, I need all the help I can get. Using logic, I would guess that, given a coil with a primary and secondary winding, there should be 4 wires / 4 connections, two wires from each coil (the start of the windings and the end of the windings) But it appears there are more connection points than that. I found a post from Ron that said there are 12 turns of 38 ga wire for the primary winding on the RF coil, which is GREAT information. Can anyone enlighten me as to the number of windings for the secondary? Ditto for the OSC coil. I'm sorry if this makes me sound like a total dummy. I tried to hide the fact as long as I could Thanks

[skyscraper]

Don't panic!

I have a bit of info. Notes are looking at the bottom of the coils, counting the lug pins clockwise. This is for the early code 123 version, using the 36 tube as oscillator.

For the oscillator coil, the tickler is the small coil on the outside, over a band of probably disintegrated plastic. Heat it with a heat gun, unwind it, and clean the plastic off. Bake it for an hour at 200˚ to get moisture out. It is 27 turns, clockwise from the bottom, of 34, 36 or 38 gauge wire. Lug 1 goes to the top of the coil, lug 2 to the bottom.

The rf coil primary was also bad on mine, it is almost exactly the same as the osc tickler in terms of procedure and appearance. Make sure you cook it! It is 13 turns of 34 awg, clockwise from the bottom, lug pin 1 is the top, 3 is the bottom.

Wind the coils right out of the oven. Use a piece of thin plastic to insulate the new and old coils. I used a strip of ziploc bag. Use hot glue to secure the ends of the wire while winding. Once it's wound, check resistance and spray it liberally with clear lacquer.

I just finished my 89, beware the oscillator circuit is ridiculously finicky (if you have the 36). Some other info can be found on my thread 'Model 89 Cathedral'. It was my second radio, and pulls in stations all the way to Canada at 680 miles away.

Good luck,
Will

[skyscraper]

I also have a before and after picture if you want to see what it looks like.

Another thing, the rf coil has five lugs, the secondary is tapped. The oscillator coil has six (a wire coming from the top) for the primary, secondary and tickler.

[NostalgiaRadioTime]

Wow! Thank you so much Will. That's going to be a big help. Yes mine has the 36 tube. After a total recap & resistor replacement, all I got was static, squeal, and motorboating. That's when I discovered that even though all the tubes were lit, I was getting nothing through the 36 and the 44 next to it. And no response from the antenna jack either. I will look further into these coils after work and I'm sure I'll have more questions. By all means if you have before and after pics of the coils please post them for all to see. Thanks again!!

[skyscraper]

Here's pics. The before is the oscillator coil, the after is RF ready to go back in. They look essentially the same.


[Image: https://lh6.googleusercontent.com/-Jm12L...C_7975.JPG]

[Image: https://lh5.googleusercontent.com/-OXK_6...C_7982.JPG]


At the moment, my oscillator circuit requires a jumper lead connected to the top of the primary in order to oscillate. Not connected to anything, I don't have any idea what it's doing electrically. A user here said to replace the tube. You might want to get a spare 36 or two.

[Raleigh]

Nice looking rewind job. BTW, the lead attached to the primary might be what they used to call a "gimmick." It's a piece of insulated wire, usually not connected to anything at one end but sometimes routed near another conductor, just to add a tiny amount of capacitance to a circuit.

They're often found on coils & transformers of various types as a short piece of magnet wire routed across the coil at 90 degrees to the rest of the windings, connected at one end only.

Gimmicks are sometimes seen on tuning capacitors as a piece of regular insulated hook-up wire, sometimes running from the oscillator section to the antenna section, but only connected at one end or the other.

Occasionally, you see a few turns of wire wrapped around a cylindrical paper capacitor.

A gimmick is sometimes represented in the schematic as a stray line with a curlicue in it, connected at one end of a coil, which tells you only that it is there, not how it is supposed to be run. Sometimes gimmicks are not seen in the schematic at all, but they need to be there all the same.

[skyscraper]

The lead isn't anything that was there originally.

After I restored it and nothing came out at all, I disconnected the antenna and hooked up a scope probe to pin 2 of the 36. The oscillator was working perfectly. I reconnected the antenna and the radio played fine. Disconnected that lead, and it stopped. Instead of the probe I just have an alligator test lead now, that works the same way.

It seems to me the capacitance would be miniscule, a fraction of a picofarad. I guess that's a statement of how poor the oscillator circuit is. Anyway, I just bought three 36 tubes on ebay, I hope that will fix it.

Greg, I'm sure you've seen it a dozen times, but replace the cathode bias resistor on the 36 tube with something less. I used 6k8 ohms.

[NostalgiaRadioTime]

Hi Will,

I can't thank you enough for your help. Just so we're on the same page, looking at the bottom of the coils, with the mounting bracket facing you, the lugs go clockwise starting at the bottom left, like this crude sketch I made of the RF?
   
That said, I get continuity between lugs 1 & 4, and lugs 2 & 5. Can you identify which 2 lugs are the primary connections and which two are the secondary based on that sketch?

Here's a similar sketch of the OSC coil.
   
Lug number 4 has the inner coil attached (soldered) to it. Is the numbering correct on this coil based on what you found, again looking at it from the bottom with the mounting bracket facing you? On this coil, I get continuity between lugs 3 & 5, and the center wire (dot on sketch) & lug 4. Based on this, can you identify which lugs the primary and secondary are connected to? And, also which lugs the tickler are connected to?

Knowing this would be EXTREMELY helpful to a coil winding novice like me. Thank you SO much!! And my apologies for my crude and sloppy sketches, but it was easier for me (and faster) than taking pictures and editing them, adding numbers to them, etc.

[skyscraper]

Alright, looks good.

For the RF, you shouldn't get continuity from 1 to 4 based on my coil.. I have the primary, which is the small coil that goes bad, marked 1.68 ohms on the schematic, between pins 1 and 3. Again, that's 13 turns clockwise, with the bottom of the coil (nearest the lugs) connected to 3, top to 1.
The secondary is something like 100 turns, connected between lug 5 and 2, with lug 4 going to a center tap to select the police band. I don't have more specific notes on it.
I would clean off the old coil (make your own notes, just to be sure. Drag a needle across the windings to count them). Once you do that check the measurements again, it's possible they are shorted, but not likely. Our two radios could also have different parts, I suppose. You aren't talking about the antenna coil, are you? That one also goes bad, from lightning.

For the oscillator coil, the culprit is the tickler winding, on the bottom of the outside coil. Over a piece of decaying celluloid. It is between lugs 1 and 2 on your diagram, 1 at the top, 2 at the bottom. 27 turns. FYI, it is erroneously marked 5.25 ohms on the schematic. Expect about 1 ohm from your new coil.
The primary is the small form inner coil, connected at the top to the loose wire, and the bottom to lug 4.
The secondary is the outer coil under the tickler, lug 5 is the top, 3 is the bottom. All are also wound clockwise looking at the bottom.

I was dreading the rewind, but it went really smoothly. The hardest part is getting them out around the capacitors. Let me know if you need any more info, everything is still on my 'work bench'

[NostalgiaRadioTime]

Excellent!! Thank you, thank you. I printed this out and will compare it to my coils after work tomorrow night. Heading to bed now... 5:30 am wake up and another work day comes WAY too soon

[stanleybadams]

Why would I have to bake the coil?? The problem is caused by the long term interaction of the nitrate cellulose with moisture in the air. If I strip off the old winding and the enamel covering on the secondary is good all I need to do is place a small insulator strip and wind over top of that. New plastic and new wire should cure that problem as the new materials no longer have that problem.

Just 2 cents

Thanks

Stan Adams

[Steve Davis]

Why would I have to bake the coil?? 

If you don't, the oscillator my not work. Sometimes there is enough moisture in the coil form to keep the oscillator from working.

Bake the form first, rewind the coil then, spray a couple of coats of clear lacquer or enamel to seal the moisture out.

Steve

[Radioroslyn]

Hi Greg
Just to be clear you don't want mess with the large windings on either coil just the small windings at the bottom. The large windings don't go bad very often. Mark a couple or months ago unwound both and it's kind of headache.
Just trying to save you some time!
Terry

[jerryhawthorne]

Great info for those of you that are visually good and with steady hands. Thanks for the information. I just send mine to Ron and work when they come back! Thanks Ron for the service, some of us just don't have the ability to work with fine wire.
Jerry

[Ron Ramirez]

...I don't rewind them anymore...