No Sound in my High Speed. Stopped working during game play. Before that it was missing some sounds but replacing op amp solved the problem. Currently no sounds in speakers, but logic seems to be working ok. If -12v is not connected I can hear very low sounds

Have already change U1, U2, U3, U4 and U5 and cabinet pot (new 10K soldered directly in mpu pins for testing purpose).

Thank you wayout440

Have disconnected -12v because by some reason VR1 turns red hot when -12v is connected. Also, pot was connected on MPU J16 because I was testing without aux sound board connected (Leon test eprom). Again with -12v connected both op amps 1458 have -12 at pin 4 and +5v at pin 8 (not 12 has you mention). Sound completely muted and VR1 almost on fire. Data lines are Ok at DAC mc1458 but +ref is 0v????. Don't know how to test DAC output...

What should be the voltage at -Ref and +Ref of DAC Mc1408?? I'm getting close to 0v on both (pin 14 and pin15 of U2)...Vcc is ok at 5v...

Thanks wayout440!!

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Anyone with a high speed or grand Lizard that could double check voltage at -Ref and +Ref of DAC Mc1408 (pin 14 and pin15 of U2)?

thanks

VR1 is getting hot when connected on bench using a ATX power supply!!!?? When using power from machine PS no heat in VR1...anyway I'll have to pass the bench test and move back all boards to the backbox...

Changed a few components and zr1 is holding now. logic is working also but the problem persists. Removed TDA2002 and connected audio signal to external amplifier and everything works OK so th problem is now confined to the TDA circuit. All components are Ok.

What could be the cause of no amplification?

Ok...made a replica of the sound amplification circuit in my breadboard and the amp is working ok. Started moving components from my mpu to the breadboard until it stopped when used capacitor C5. It looks the cap was the culprit and now the amp is also working. In the meantime, back to an old issue. Missing some sound effects...

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OK now! Something killed sound Eprom U22. The chip was blank with no code.

ZR1 getting hot was related to my ATX power supply. When bench testing with Leon (R.I.P.) test eprom it is required a jumper between 5v and ZR1...ONLY if you don't have 12v connected.

Everything working now.