#286
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In this TV, the Admiral 14R12 there are a total of 10 mica caps used. 1 is a high voltage (1500V) in the yoke which was not replaced, 3 in the RF/IF section, and the rest from the IF section on.
So out of 9 micas, there appears to be no problem replacing those 6 in the sweep circuits etc. That leaves 3 120pf micas (C17, C18, and C24) that seem to be subject of whether to change them or not. These cost me $2.39 each because I ordered 1% caps. A total of $7.17 for the 3. I do think the parts list listed at least 1 of them 3% hence why I got all three at 1% from Just Radios. I know overkill. I replaced 9 electrolytics, 29 paper caps, 8 disc caps, and 9 micas. A total of 55 caps. To me changing 52 caps and then changing 3 more to have them all changed just makes better sense to me. Especially when we are warned not to even move the micas because it can cause the lead/case seal to fail and that will lead to problems down the road. This can happen when changing the resistors, etc. So I just change them to eliminate any problems, if any, by keeping 65 year old micas. As several other posters have said, they do find micas in the RF/IF section failed. I know there are those who really enjoy trouble shooting and good for you. I enjoy just as much a finished product that was made as good/better? as new when I'm finished and I don't have to wonder if an old component that I could have changed and didn't is going to fail latter on. If I had a good source for the very low value ceramics, I'd probably look close into changing them as well. Like I said " Everybody sees this hobby through their own set of eyes and gets out of it what they want to. Neither is right or wrong. But different approaches." |
#287
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Where did you hear that? I've always heard and understand the merit of not changing the lead dress in TV and FM because at those frequencies the small change in capacitance is similar in electrical effect to turning a slug in that circuit a few times.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#288
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Quote:
I've also been made aware of lead dress. EDIT- I went to the ARF Elecrtical/Mechanical forum and did a search using "mica leads". I came across at least 6 different posts about the problem with micas and their leads being twisted or moved. Last edited by Crist Rigott; 11-17-2016 at 11:25 PM. |
#289
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Like I said " Everybody sees this hobby through their own set of eyes and gets out of it what they want to. Neither is right or wrong. But different approaches."
Well said! |
#290
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I agree Crist, I have read many times before not to twist or move the leads of these bakelite micas too much as you can break the seal. How much merit that statement has, I don't know. For all I know, the seal was never really there from the go. As for lead dress, it should be kept as similar to the factory as you can. If you go through all this trouble, the set in my opinion should be re-aligned anyway, so minor changes in the lead dress will be a non issue.
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Audiokarma |
#291
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Crist,
You did a fantastic job on your Admiral 14R12. What did you use to clean / polish the plastic screen? Ed |
#292
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Quote:
3M Headlight Polishing Kit. |
#293
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OK, I got the pencil box door. The escutcheon that it came with while being the correct part number the rev code is different and when compared to the one on the TV, there are slight differences mostly in the printing size and slightly different locations. My guess only a trained eye would catch the differences.
With that said, does anybody know how to remove the pencil box door clips and the door so I can use them on the correct escutcheon? Of course I'm being careful here not wanting to break anything. Thanks. |
#294
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Quote:
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#295
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Kevin,
Worked perfect. I can breathe now! Thanks. |
Audiokarma |
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