Kay 704 Vanguard tremolo issue

[glebert]

Got this pretty cool all solid state 60's Kay 704 with an out of control tremolo oscillator, up in the 100's of Hz or more. Just found the correct schematic (I think) and haven't probed yet. Since this is tag board construction tracing the circuit can get a bit confusing. Anyone have a good place on what components to check out first? I'm guessing the caps and resistors near the speed control pot, but are there a couple components that really set the oscillation speed range? If I had to guess I'd say R4 and C3, but that is a pure guess. The speed control pot does vary the oscillation over a broad range (just too high), so that seems to be functional.

TIA,
Greg

kay704_2nd.pdf

[x-pro]

Sorry, got confused with the components in the Q1 circuit.
The component position numbers are nicely labeled

Yes, you're right. The specified elements of the multivibrator can be related to the speed setting elements.

[g1]

C3 and the three caps named C9 would be the first on my list.

[glebert]

Oh yeah, didn't notice that they still named parts on this in reference to a parts list, not as specific components. Thanks for the guidance!

[glebert]

C3 and the three caps named C9 would be the first on my list.

This was it. Had to replace all four of those caps. Tremolo is working now, but a bit thumpy. This is a great sounding little amp, though.

[glebert]

This was it. Had to replace all four of those caps. Tremolo is working now, but a bit thumpy. This is a great sounding little amp, though.

Replacing the 1 and 2 uF caps where the tremolo feeds into the input transistor took care of the thumpy trem. These caps did not hold up well over the years.