Quoted from Andy_B:After re-fitting the CPU board I have no sounds at all.
Can you test for negative 12 volts at U-2 pin 3. You may have a cracked header pin on 1J-17 or 3J-6.
(Topic ID: 254969)
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Sounds are stored ans processed in the yellow box area. When the game calls for a sound, it is selected from the green box area. Voice clips are at the top yellow arrow and digital processed sounds are on the lower yellow arrow. The voices are amplified thru 2 op amps, sound are amplified thru Q-1. Both sets of sounds come together at the very left and go thru another op amp as combined sounds and leave the board to go to the background sound board and volume pot. Then the sounds come back in from the volume pot red arrows and to the main amplifier and leave to go to the speakers.
hss (resized).PNGSince you have no sounds at all now you need to go to components that affect both speech and sounds and background sounds. This is why I had you check the -12 volts as this powers the amplifiers. Other things to look at would be the volume pot, C-2, C-3, U-1 on the CPU board. Also check for the -12 volts on the background sound board on on side of C-6.
Quoted from Andy_B:Is an oscilloscope required for full analysis of the sound circuitry?
It is very helpful. Since you pulled the CPU board, you removed 1J-17 connector. The Sound board is also tied to 1J-17. You may have pulled a wire from the sound board power connector causing all the sounds to stop.
There is a cable that connects the background sound board to the CPU board, disconnect it from the CPU board. Then disconnect the other cable from the background sound board that goes to the volume pot and connect it to the CPU board where you just disconnected the other cable. Play a game to see if game sounds work. There won't any background sounds tho. But this will tell you which board is acting up.
Quoted from Andy_B:Is there a quick and easy way to test the amllifier chips?
You are going to need a Oscope for this type of testing.
Quoted from Andy_B:Will this be suitable?
I really can't say as I have never used a PC type Oscope. I just have a 25 year old 2 channel Tektronix.
pasted_image (resized).png 1 week later
Quoted from Andy_B:Unless I have wired it wrong
You have it correct for cpu sounds only.
Quoted from Andy_B:I will have some time over the next few days to shotgun some of the cheaper chips and hopefully get a result.
Start with caps first. C-2, C-3, C-5, C-8, C-9, C-10, C-11, C-12, C-13 and C-15.
If that doesn't fix your issue then replace U-4 and U-5.
If you still are not working then replace U-1.
3 months later
Quoted from Andy_B:In MUSIC TEST the background music is present but faint. In SOUND TEST all the sounds are present and at the correct volume.
Could this be the op amp(U-9)or Q-1 on the sound board?
2 months later
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