yeah, I sort of half did that and then switched to the transistors thinking they might be the problem. I switched the two largest (in terms of uF) capacitors. I'd assume that that would influence the timing of the percussion (i.e. voltage in the circuit). Would it also influence the gain?
Its also got a strange set-up. In addition to the NE-2s with the photoresistors, It has an NE-2 across the main ground for the board and the main input. Before I switched transistors and half the capacitors, the bulb would flash in sync with the percussion, kind of like a tremelo. Not sure if it is supposed to do that. Now the bulb stays lit or stays off. So strange.
I'll let you know what happens once all the caps are replaced.
Anyone know how this unit is actually supposed to function?
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On Tue, Aug 11, 2009 at 8:11 AM, Scott
<painintheamp@...> wrote:
--- In
vintagesynthrepair@yahoogroups.com, "toxlose" wrote:
>
> Having trouble fixing the percussion circuit (PA-24) in a Farfisa Compact deluxe.
>
> As far as I can tell the circuit is somewhat intact. Tab on activates a neon bulb and LDR that sends the signal to PA-24 and then out to the preamp.
>
> Just changed all 4 transistors in the PA-24 board but the percussion still doesn't work right and as before, the output volume for both the treble and bass percussion is far lower than when the tabs are in the off position.
>
> Anybody have a similar problem before?
> -Rick
>
A unit of that age?...I would change out whatever electrolytics are around it