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Irem M92 - Hook - no sound

Yippikaye

Yippikaye

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Hello Guys and Gals,
I got a working Irem M92 Hook game but with no sound.
So I first started by removing and changing all the brown capacitors.
I still have no sound.
My skills an tools are limited but I would like to learn.
I swapped Mother Boards and I got sound.
Rom Board is original.
I already checked the previous thread on a similar issue on AP ( https://www.arcade-projects.com/threads/irem-m92-no-sound.5634/ ) and some of @caius repairs ( https://www.jammarcade.net/?s=M92&searchsubmit= ) but I don't know where to start.

Feel free to ask me any question/picture and thanks in advance for the help.

Yippi
 
Yes, there is some corrosion, but I did a continuity check and it's OK, I cleaned with 95° alcohol
No lifted pads,
 
Sounds like it is no good. Send it to me and I will dispose of it for you :D
 
A few possibilities:

1) Run you finger along the traces underneath the amplifier with the board powered on. If you hear crackling from the speakers then the amp is probably okay. If you don’t hear anything try replacing the amp.

2) Dump the sound CPU ROMs with an EPROM programmer and confirm that that match the checksums in MAME.
The Sound ROMs are labeled “sh0a” and “sl0a” and I believe they’re at IC 14 and 17 on the board, although MAME labels them 27 and 28.
If either chip doesn’t match MAME then you can program a fresh 27C512 EPROM to replace it.

3) Make sure the two jumpers next to the Sound CPU aren’t missing and are not set to “N”.
Assuming your board isn’t a conversion from another M92 game, the CPU will be expecting encrypted code. Converted boards change the Sound CPU jumpers to “N” so they can run decrypted sound CPU code.
 
1) AMP ok, I can hear crackling
2 My Rom Board works fine with another mother board,
Do I have to dump the Roms anyway ?
3) Can you point me to Sound CPU number ? I don't want to make a mistake :)

Thanks
 
Hmmm .... if you get sound when installing the ROM board on another M92 mother board then the problem is something else besides the possibilities I listed.

Check the jumper settings between the two mother boards and make sure they match up.
 
Anybody can help me with the resistors values ? I can't identify them on my board :(
I'll change them and see if the problem is still here
 
I dont think its your resistors. Try checking the opamps and work backwards on the sound circuit until you get sound. If you dont get analog sound at all then its further up the chain.

Do you have an audio probe?
 
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