Sega System 32 Motherboard: No sound

Fox1

Bub & Bob's Bubble Buddy,
So I'm trying to figure out why there is no sound coming from the motherboard. When I do a RAM test, it comes back with IC16 is bad and all the rest are fine. The IC16 is located right by the audio area/Z80, so I thought that could possible be the trouble. However, I replaced it and the problem remains...it still comes up bad as well. I used a known good replacement.

 

aha2940

AH, A, COLUMBIAN!,
Hi

If the IC reported as bad was replaced and the problem remains, then I would check the traces going to/from that IC and the rest of the sound system. I am not familiar with this board in particular, but that's what I would do.

Regards.
 

Fox1

Bub & Bob's Bubble Buddy,
I forgot to mention that the traces looked good too..not even a single suspect one.
 

Xian Xi

JammaNationX,
Also check if there is at least a hum, if no hum the the output caps could be bad, bad amp, bad potentiometer etc.
 

Xian Xi

JammaNationX,
http://www.datasheetarchive.com/dlmain/Datasheets-16/DSA-317071.pdf

That's the chip. When I turn the audio on, I hear a crackling sound and that's about it.

If it's saying the SRAM is bad and you replaced it and nothing changed then you need to check the control lines on the SRAM.

20 - CS1 (Chip Select)
22 - OE (Output Enable)
27 - WE (Write Enable)

They are all active low so if any are high then they aren't active but if any are just dead then you have a problem somewhere else. You can then trace to see what they connect to, most likely a TTL chip.
 

Fox1

Bub & Bob's Bubble Buddy,
Question, even if the reset on the z80 registers as high, could the z80 still be the problem?
 

miisalo

Astra Superstar
I have the same problem, socketed the IC16, replaced with a chip that _should_ work (I have same as original chip coming soon). I was suspecting the Z80 too. This is the clock signal for Z80

17115317528_835f74f599_c.jpg

The other 8Mhz signals coming from the buffer/driver chip look fine, so either something weird is happening in the Z80 or one of the outputs of that clock driver is done.

Reset stays high.

I remember seeing something weird in the address lines, going to scope them now.
 

Xian Xi

JammaNationX,
Does the Z80 at least register low during power up for a split second? If it doesn't the you need to check the reset circuit.
 
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