VintageKustom.com: Repairing Kustom Amps

Re: Misprint or error [message #17071 is a reply to message #16938]

Thu, 10 May 2012 06:43

stevem
Messages: 4735
Registered: June 2004
Location: NY

Senior Member

untill you get a reverb pan back in the unit I would make up a shorted RCA jack to go into where the output cable would plug in, with out this you have a open gain stage ( if the gain stage works, see below) and may be picking up noise.

If you plug the cable in this output jack and get a buzz when you touch the tip, then thats good news and means that the recovery side of the reverb board is working and in all liklyhood when you pop in a new reverb pan with a ground to the chassis you will be good to go.

The blue wires in the amp are the signal wires, if you unhook them from the output driver board you can test out the noise level of just this board itself, when all is well these boards are pretty dam noiseless!

I cut the wires at a place where I can just red butt splice them back togethere.
As a matter of course I would replace the first two or three transistors after the input jacks on all four channels, as most times this is the root of alot of hiss and crackle, it takes way less than 3/4s of a volt RMS of signal input to drive these amps to full output, and if a former owner drove any of the channels witha stomp box its all too easy to harm the input gain stage transisor!

If your O-scope still works you can trace back up stream form each channels blue output wire and find any other noisy transistors, or with a volt meter leaky coupling caps.

Once you get it back in good shape I mod I have done with mine for guitar or bass use is you change the tone caps in 3 of the 4 channels for a different frequency range, then with a out board a/b/c/d foot switch that I made, I can switch to different channels for tone and volume changes.

[Updated on: Thu, 10 May 2012 06:50]

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