This is a continuation of my sound issue in a previous post.

My sound card stopped working, but I was able to get most of the sounds back, but not all of them. The test sound works solidly now, but no sounds on the solenoid diagnostic test. When I ground the pins at 10J3, Pin 2 doesn't create a sound but 3,4,5 and 7 do ... just like in viperrwk's youtube video.

When I ground the tab on the matching TIP120 on the driver board, no sound. But I replaced it and the 2N4401 because they looked rough. Tab has +5v.

During game, I get intermittent sounds, like one pop bumper that triggers sounds but not all three. When I hit a drop target with the red arrow lit, I get a sound, but nothing when arrow not lit and no rollovers/spinner sounds. And the background sound has come on about twice during testing. But not regularly.

At a loss where to go now.

Background: The game got flaky and the MPU locked up, so I replaced sockets on the MPU and replaced and 40 pin on both sides. (A bunch of other stuff, too.) While I was at it, it bought a new three ROM set to replace the 5 set. That got the game working but the sound was out. When I got the game several years ago, I did a cap replacement (and it worked great for two years).

Here's what I've done, or learned:
1. The socket for the PIA was newer so I left it, but replaced the ROM and processor sockets. (I've checked continuity on all sockets and it seems they're all ok.)
2. Tried different 6821 PIA and 6802 processor chips.
2. Socketed and replaced the 4050 buffers.
3. Socketed and replaced the 4068 IC
4. PIA pins 1-9 to DAC get good logic probe signals during sound test.
5. All 10J3 header pins have +5V
6. Replaced the bridge rectifier but probably didn't need to. But I am getting good voltages in places where I know to test. See question later.
7. Re-soldered 10J3 pins on the sound board and the 2J9 on the driver board.
8. Replaced some of the disk caps C8, C9 and C11 because it looked like the legs had cracked away from the coating.
9. +12V and +5V on top and bottom pins of the voltage regulator IC11.

I'm wondering if ...

1. Should I have voltages at all of the big caps? I get +12v at +C29, +5V at+C27, +5v at C10, +11v at C14, and nothing at C30 and 55 mV at C13. Are C30 and C13 suspect?
2. My sound ROM is the culprit.
3. Is the DAC bad? How to test?

Thanks for reading. Help is very much appreciated. Pete

Thanks for your detailed guidance, barakandl. Pinwiki confirms that the sound commands from the driver board come into Pins 2,3,4,5,7 at J3 (the only wires at the header.).

Here's what I've observed:

1. IC8 Checks out with P11 and P12 going low.
2. PIA P11 also goes low.
3. IC4 does not behave as expected. All sound INPUT pins to IC4 go High to Low when the J3 pins are grounded. Now, P13 is neither High nor Low without grounding J3 pins, and goes High for 3,4,5,7 BUT NOT J3 P2 (my missing sound). (The only pin that starts low is P8).

So I'm guessing this indicates a fault with the 4068 IC4 since I'm getting input activity on P2 but no output activity. The 4068 is new from Mouser. I need to see if I bought 2, which I normally do. If there's more I need to check, I'd appreciate the direction.

thanks again.

Pete

barakandl Big, big thanks. I went ahead and bought some more 4068's from Jameco, because the one I had didn't have logic activity on IC4 pin 13 when grounding 10J3 pin 2. Now the sound is completely back. I appreciate your clear info and time spent helping guys like me.