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Author Topic: replacing capacitors drake tr3  (Read 1586 times)
KC9VZB
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Posts: 48




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« on: January 06, 2013, 06:12:52 AM »

the saga continues.Thanks for all your help.I got radio plugged into var-yack and voltages are close to speks.Question is can I replace .47 paper caps with .47 dipped mylar ?There was both in set originally. It had more signs of life before I changed them out.but it had higher voltage too.

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KE3WD
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Posts: 5689




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« Reply #1 on: January 06, 2013, 06:52:52 AM »

Yes, just make certain that the voltage rating of the new cap is equal to or better than the one you are replacing.


73
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AC5UP
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Posts: 3864




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« Reply #2 on: January 06, 2013, 08:17:10 AM »

Many tubular condensers have a black line at one end denoting the outside foil. Usually that end of the condenser will be closer to ground as a way of adding some shielding to the AC circuit path. If your dipped mylars are marked as such, try to retain the outside foil position. If not, it's not a major issue.

In the case of point-to-point wiring new parts should be 'dressed' like the old parts as condensers in particular can be intentionally moved away from filament lines & such to minimize inadvertent signal coupling.
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N4NYY
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« Reply #3 on: January 06, 2013, 08:48:55 AM »

Mylar (Polyester) or Polypropylene are the most common replacements for those caps, and are superior in performance. 
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K1DA
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Posts: 500




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« Reply #4 on: January 13, 2013, 06:26:46 AM »

Not sure what "signs of life" means.  Is the calibrator functioning?  You should see at least S 9 to 10 over on the lower bands with it on.  Sometimes a receiver which is working properly generates less nise than one with some failing parts.  Are all the voltages from the AC3 or AC4 correct within 10 % or so?
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