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From: jws@cica4.mlb.semi.harris.com (James W. Swonger)
Newsgroups: sci.electronics
Subject: Re: Suggestions for an intermittent hum problem.
Keywords: 60 cycle noise audio
Message-ID: <1991Jan28.153323.21731@mlb.semi.harris.com>
Date: 28 Jan 91 15:33:23 GMT
References: <1991Jan28.144723.16008@cbnewsh.att.com>
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 A SAM's may be available for your unit. Try the TV Repair/Electronic supply
places in your area.

 A hum that changes volume with the volume knob would indicate an open/
intermittent contact etc. upstream of the main amp.

 A hum that is constant is more indicative of power supply problems. 
There may be a poor connection at one of the recitifiers or caps.
Some amps and rcvrs have separate supplies for each channel to give
better isolation. See if you can cause the problem by wiggling the filter
caps and rectifiers.