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Fox1
05-08-2014, 09:44 PM
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.

http://i1294.photobucket.com/albums/b606/hyperneogeo/th_hqSyh9E_zps90f95e46.jpg (http://s1294.photobucket.com/user/hyperneogeo/media/hqSyh9E_zps90f95e46.jpg.html)

aha2940
05-08-2014, 09:59 PM
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
05-08-2014, 10:01 PM
I forgot to mention that the traces looked good too..not even a single suspect one.

Xian Xi
05-08-2014, 10:30 PM
What kind of chip is IC16 exactly? It's likely the Z80 is failing.

Xian Xi
05-08-2014, 10:32 PM
Also check if there is at least a hum, if no hum the the output caps could be bad, bad amp, bad potentiometer etc.

Fox1
05-08-2014, 10:53 PM
What kind of chip is IC16 exactly? It's likely the Z80 is failing.

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.

Xian Xi
05-10-2014, 04:08 PM
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
05-12-2014, 03:07 AM
Yeah, all 3 of them are active high.

Tyranix95
05-12-2014, 03:35 AM
Looks like a DEAD ADDER PCB. :eek_2:

Fox1
05-12-2014, 03:47 AM
It's not adder lol.

Xian Xi
05-12-2014, 05:53 AM
Yeah, all 3 of them are active high.

Check what they are connected to.

Fox1
05-12-2014, 06:49 AM
Check what they are connected to.

20 goes no where, 22 goes to Sega Custom 315-5385, 27 goes to Sega Custom 315-5385 as well

channelmaniac
05-13-2014, 11:56 PM
Replace the Z80 CPU.

Fox1
05-14-2014, 01:54 AM
Alrighty, I'll give that a shot. Thanks

Fox1
05-14-2014, 06:01 AM
Question, even if the reset on the z80 registers as high, could the z80 still be the problem?

channelmaniac
05-14-2014, 09:29 PM
Reset will register low for a split second on power up then stay high.

Fox1
05-15-2014, 02:55 AM
Okay, I'll give it a shot tomorrow. Need to go buy a mount for it.

Fox1
05-15-2014, 12:44 PM
Changed it, no change :/

miisalo
04-29-2015, 05:47 AM
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

24917

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
04-29-2015, 05:55 AM
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.

miisalo
04-29-2015, 06:08 AM
It's low and jumps to high with tiny delay, so reset circuit should be fine. Scoped address lines and all but A0 jumps between low and high.

miisalo
04-29-2015, 03:35 PM
Installed socket and another Z80. Now I can sometimes hear few cracks when powering the board. Same damn problem that fox has...

mainman
04-30-2015, 12:20 AM
Damn it, Damn it. I fixed this problem before but can't remember what the cause or solution was.

miisalo
04-30-2015, 11:20 AM
Hopefully you remember in some point. I'm going to scope a bit to see if I find something weird. I do have 32 channel logic analyzer too.

Edit: that clock signal is shit but works, using another source pin, signal is better but same problem. Also noticed that without Z80, system does not boot at all.

miisalo
05-12-2015, 11:58 AM
I installed exactly same as original sram and while pressing some of the chips I got corrupted sound and IC16 actually passed the test few times. I have now reflowed three custom chips but still no sound and IC16 is bad again.

The board is quite badly bent so it's probably at least partly issue with solder joints...

Fox1
05-12-2015, 02:40 PM
It's honestly a motherboard that will drive you bonkers. I've had 2 problems with System 32 boards. One being that IC16 sound problem and another being a weird graphic glitch that pops up randomly. The first guess was obviously a loose solder joint, but neither Ken (at Irepairsega) or I could find it and it drove us bonkers. We also tried looking to see it was a bad ram that was randomly glitching to no avail.

miisalo
09-12-2015, 04:00 AM
Should Z80s A0 line connect to any of those 74244s like other address lines? I have soldered socket for the z80 and can't quite see the traces. I managed to get rid of most of the ringing in the clock line and found two legs I had to reflow in one of the sega chips but still dat ic 16 bad and no sound.

theGau
02-15-2017, 04:27 PM
I hate to revive a 17 month old thread but I am having a similar issue with a Rad Mobile, did anyone figure out why this system's sound dies out?