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FM motorboating on Philco 48-482
Micro9
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#1

11-01-2009, 10:34 PM
Need help on a Philco 48-482.BC and SW work great after recap but FM is very weak and motorboats when volum is rasied.FM was bad before I recapped it.All resistors are with in tolerance around the FM1000 and 7B6 tube.....Any ideas????
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Micro9
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#2

11-02-2009, 11:53 PM
FIXED.....One of the "NEW" E-caps I put in went belly-up....Checked it before I put it in..It checked good...went belly-up after the power hit it.....
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exray
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#3

11-03-2009, 09:00 AM
How did you pin it down? Did it swell up or pop?

-Bill
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Micro9
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#4

11-03-2009, 02:34 PM
No I used my ESR meter and started from scratch again....Per the Schematic (I) part of the old Cap went to filter the FM.I cut the orginal cap out of the ckt before I put in a new cap in its place.....The cap looked just Like new but was shorted....
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codefox1
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#5

11-03-2009, 06:29 PM
Interesting. I have seen problems with motorboating caused by an open filter capacitor quite a few times, but a shorted one would either burn up the dividing resistor or cause the stages fed by it to cease functioning. Glad you got the set working again, but I'm afraid I missed something.
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Micro9
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#6

11-03-2009, 09:13 PM
There was a 3300 ohm R404 that was also burnt. It wasn't open but was @3.5 meg and I replaced that also....
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