I just finished another restoration on a Model 89 cathedral with the 36 autodyne. I know I have probably beat the oscillator tickler coil thing to death. But this time I got it to work first time. Maybe this posting will help someone in the future.
27 turns starting from pin 1 ending on pin 2, turning clockwise looking from the bottom of the coil form, using #38 wire. Pin 1 is the first one to the right of the mounting clip looking from the bottom. Worked perfectly and oscillates across the entire band.
In the past, I tried #34 and #36. I know people will say that the wire size is not critical for a ticker coil, but only, only after I went to #38 wire did I get it to work. With this number of turns, and the very thin #38 wire, the resistance measured about 5 ohms, which is very close to what it says on the schematic. I took this as a good sign.
When I brought it up, it squealed like the dickens. But the tube shields were missing. I found a tube shield for the the 75 tube, and that fixed that.
Mark K8KZ
(This post was last modified: 12-26-2015, 01:09 PM by markmokris.)
Mark,
What do you recommend I use as an insulator between the two coils? I'm talking about the tickler coil being wound on top of the other coil. From what I've read there's a lot of differences of opinion on what material should be used.
I'm just starting an 89. Do you have any advice on the antenna call?
(02-16-2016, 02:33 PM)Hugh C Wrote: What do you recommend I use as an insulator between the two coils?
For an insulator, I just used scotch frosted tape. I lay in on backwards with the sticky side out. This holds the wire in place as I wrap each turn. In order to hold the tape in place, I tape it down with some tiny pieces of additional tape around the perimeter.
Mark, do you cover or coat the tape and tickler coil with anything? I was concerned about the edges of the sticky tape attracting dirt or metal filings.
No I haven't been doing that. I understand your concern, but I haven't found it to be a problem. Ron has suggested spraying the finished coil with clear lacquer. That would negate the stickiness, but I have not resorted to that.
Mark K8KZ
(This post was last modified: 04-28-2017, 06:39 AM by markmokris.)
Ok so I gave your method a try and it came out pretty good. I used some polyimide tape that I found on Amazon that has really good dielectric and temperature specs. I used 27 turns of #38 like you suggested and I'll be testing it soon.
Always good to learn from others' experiences.
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