Taito sound PCB repair help required

[petercasino]

I'm trying to repair a Taito sound pcb for a Continental Circus. Originally I was getting very low volume (almost zero) so I replaced the audio amplifiers (MB3735) and most of the capacitors in the analogue section of the circuit board. The circuit diagram for this part of the board is:

I'm now getting sound at the correct volume (though slightly distorted) but the sound consistently goes off completely then back on as you play the game. I've taken a video of what happens here:

https://www.dropbox.com/s/pfw02vmstuyqxsj/IMG_0622.MOV?dl=0

I've also replaced the TL074's in the stage before the power amps but it hasn't made any difference:

I'm wondering whether the TC0060DCA's need replacing but they seem to be impossible to find. Anyone any ideas of what might be causing the problem - could it be a problem before the DCA's?

Any help would be much appreciated!

Mike

 

[philmurr]

Can you check where the sound actually stops, is it in the pre stage or the power amp stage?

Also what are the /mute signals doing?

 

[petercasino]

Would I use a logic probe to check the mute signals?

What would be the best way of checking the output of the pre stage - would that be to measure the voltage at SIG-F and SIG-R?

 

[petercasino]

I've checked the mute signals and they are stable at 3V both when the sound is working and when it's off.

I've checked the signal at SIG-F and it goes off at the same time that the sound stops working from the speakers.

Does that mean the problem is a digital issue?

 

[Jon-A-Tron]

I know this goes a long way back but did you ever get to fix this issue?
I'm working on Taito Top Speed sound issues at the moment and have been unable to find any PCB diagrams for it. I found this thread as I'm tracing back on the board all the sound lines and came to the TC0060DCA custom package. The pictures of the continental circus PCB diagrams look almost identical to what I have taken to draw over the past day or so, so it's very helpful to me.