VintageKustom.com: Repairing Kustom Amps » K200-B5 reverb questions

Re: K200-B5 reverb questions [message #26243 is a reply to message #26242]

Fri, 28 July 2017 01:11

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

Looks like every resistor on the board has been replaced with the exception of the 1% metal film ones. As to the values, I wouldn't know where to start to check if they are all correct or not. I would have to assume that the values are the same as was supplied on the board, but they may or may not have been updated to the newer values.

The two RCA cables are ordinary ones with shields connected at both ends. The one jack on the board has the ground lifted.

There are three signal paths through this board. The first is the straight signal that is mixed through R820-823 and is controlled by Q807. The other two are the reverb straight signal and the reverb delayed signal.

The reverb straight signal is sent through Q805 and the reverb delayed signal is sent through Q800-803. Both of the reverb signals are controlled by Q806.

So depending upon the footswitch either the straight signal is grounded and the two reverb signals are allowed to reach the output stage Q804. Or the two reverb signals are grounded and the straight signal is allowed to reach Q804.

If the amp works with the footswitch turned off (ungrounded) then you know that the problem is on that board. You said that if you remove Q806 the noise happens the same as when the footswitch is turned on (grounded), which would make sense in that the reverb signals would be ungrounded without Q806 out of circuit.

Try grounding the input of the return circuit and see if that stops the howling.

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