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Post subject: 85 red knob problems. HALP!!!
Posted: Sat Oct 29, 2011 11:36 am
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Joined: Sun May 15, 2011 2:40 am
Posts: 128
Location: so cal, from victoria, tx
I have a "eighty-five" red/knob 112 combo. About 7 years ago i stopped playing it because of the problem im about to describe.

The tone will randomly become garbled and muddy... Just unclear and nasty. Hit it pretty hard and it works fine for a while. Then it does it again. The treble and mid pots are pretty scratchy but unrelated as far as i can tell. It does it in both channels.

Any ideas? I ook pics of areas i thought looked a little bit weird.

Image

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Post subject: Re: 85 red knob problems. HALP!!!
Posted: Sat Oct 29, 2011 1:21 pm
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Joined: Wed Mar 31, 2010 12:48 am
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Location: Tombstone Territory
The odds are favorable that you've localized the problem.

HTH

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: 85 red knob problems. HALP!!!
Posted: Sat Oct 29, 2011 3:45 pm
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Location: Indiana
Could be. The heat marks on the board aren't a problem, but a couple of the solder joints look questionable. Hmmm, looks familiar. :wink:

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Post subject: Re: 85 red knob problems. HALP!!!
Posted: Sat Oct 29, 2011 4:10 pm
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+1

But those CR9 and CR10 diodes look like they've seen some heat in the intervening years which isn't unusual for an amp this old.

Arjay

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Post subject: Re: 85 red knob problems. HALP!!!
Posted: Sun Oct 30, 2011 2:31 am
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+1 Shimmilou and Retroverbial..

A replacement of cr 9 and cr 10 and the resistor too R3X,

Solder those a least 1/4 inches space from the circuit. A few solder need repair too.


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