38-4 Speaker Problem - Printable Version

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+--- Thread: 38-4 Speaker Problem (/showthread.php?tid=1771)

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38-4 Speaker Problem - garyh1 - 03-25-2009

I have just completed recapping a 38-4 console. The radio works well now with the exception of a loud popping sound from the speaker when reproducing any lower frequencies at anything more than low volume. Would this be a problem with the speaker or is there something else I shoud be looking for. Gary

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Re: 38-4 Speaker Problem - Chuck Schwark - 03-25-2009

Check ALL resistors for in-tolerance values. Change any that are outside +/-20%. Sounds like audio stage or stages have a grid bias problem maybe and the high amplitude audio is clipping and being distorted. A scope would show this instantly.

Be sure electrolytic cap 46 (when it was changed) is wired properly; POSITIVE lead is grounded (see schematic) in this NEGATIVE bias circuit. Also value checks on resistors 62, 63, 54, 55, 46, 57. These can all shift the 1st. audio and P-P output tube's grid bias.

Chuck

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