So I’m recently started up my SBM and noticed there was no sound. I poured over the wiring schematic for the sound board and checked the test points on the card. TP 1 should have 11.9 VDC and I am reading 0.55 mVDC. I notice the voltage drop across CR1 is 13 VDC is is the same voltage I was reading at J1 pin 10. I believe this is the driving voltage for U9 which is the driving voltage for the speaker. I am thinking this is why i not getting any sound, however I wanted to get a second opinon that I am on the right track. I want to get this fixed so it can be used in the local pinball show next month. Thanks.

Well upon visual inspection of CR1, nothing appeared abnormal, however when I attempted to desolder it from the board it completely crumbled. So CR1 is definently getting replaced now. I also found that the C15 capacitor that was intalled was rated for a higher voltage that the orginal schematics called for so I’ll replace that as well.

I replaced CR1 and cleaned up the horrible solder job someone had previously done when they replaced C15 and the sound has returned. Yay!