Vintage Synth Repair

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