VintageKustom.com: Repairing Kustom Amps » K200B-2 tremolo is weak and pops when switched

K200B-2 tremolo is weak and pops when switched [message #26811]

Fri, 20 July 2018 13:44

Saransk
Messages: 20
Registered: February 2017
Location: Northern Virginia

Junior Member

Have to turn up the Intensity to 9 or 10 (Doesn't go to 11) to hear it
Looking at the circuit it looks a lot like the "Harmonic Tremolo" in some "Brownface" Fenders - 6G13a for example
Q314 looks like a "Split Load" Phase Inverter.

The oscillator seems to work and all the electrolytic caps have been replaced.
Here's where I am
1 - Q314 is weak/bad - it drives the effect.
2 - Q313 is weak/bad - it appears to be the oscillator output.
3 - CR302/CR303 diodes (look like overdrive clippers) are bad - shunting signal
4 - CR300/CR301 diodes - they connect (mix) the effect with the main signal.

I hate troubleshooting by replacement but without a scope or a function diagram "low" effect is hard to diagnose.

As for the "pop" when switching off, I assume either/both Q315/Q316 aren't working. They are suppose to cut out to prevent transiants across R343, and if they don't ground the signal you get a turn-off transiant.

Any other ideas or am I on the correct path here?
Thanks in advance
Michael

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