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Irem m92 no sound

You can get logic probes with an audio beeper as well, it won't tell you if the audio is corrupted, but it'll tell you it's present at least.

In saying that those little LM386 based probes look super cheap to make and more useful
 
It appears I have no data coming into ym2151 correct? problem is farther back still? This is quick compare between working avengers board ym2151 and the m92 in question. I know they are not identical circuit before hand but looking at the data input 0-7 appears to be nothing on m92 compare to avengers.

First avengers:

m92
 
Pin21 (serial data output) of the YM2151 is tied to pin4 of the YM3014 (serial data input), in previous post you posted a screenshot that shows that valid data is present on pin 4 of the YM3014.Now you post a screenshot where there is no data from pin21 of the YM2151 (hence the same on pin 4 of the YM3014 since they are tied together).You are doing a little bit of confusion since you dont fully know what you are doing :) .But, don't worry, this is normal when you have limited experience with arcade boards.
 
What could originate that sometimes you have valid data and sometimes not?
 
Yes sorry. If you look at the video of m92 (I test 8 different points in each video) you will see that there is some type of information on the very last pin I test (pin21) but I do not believe it is correct. It doesn't vary as it does on the working board. It has been there the whole time though.

It looks like ym2151 is still sending data out but isn't getting proper signal in (since all the data lines are static) so therefore isn't sending anything good out?
 
I think you should go ahead with what @caius suggested get a simple audio probe and see if what is coming is actually good.
 
brad808 said:
It looks like ym2151 is still sending data out but isn't getting proper signal in (since all the data lines are static) so therefore isn't sending anything good out?
Click to expand...
Probably, because the sound system is halted and not running properly.
 
caius said:
brad808 said:
It looks like ym2151 is still sending data out but isn't getting proper signal in (since all the data lines are static) so therefore isn't sending anything good out?
Click to expand...
Probably, because the sound system is halted and not running properly.
Click to expand...
that appears to be the case. The sound CPU is where I should start my check? Is there some pinout for sound cpu? All I see was clock pins on mame source but the clock seems to output fine.l
 
I forgot.Have you any chance to swap the Major Title 2 ROM board with a good known M92 CPU board?This will help you to narrow the fault in a specific board and from there start your real troubleshooting.If you don't have any other M92 boardset, ask someone for a loan.
 
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I have not been able to test rom board on another main board. I don't have one so it isn't a very good option for me.
 
caius said:
I forgot.Have you any chance to swap the Major Title 2 ROM board with a good known M92 CPU board?This will help you to narrow the fault in a specific board and from there start your real troubleshooting.If you don't have any other M92 boardset, ask someone for a loan.
Click to expand...
This.
It's so much easier when you have an other board to compare signals, swap boards.
Unfortunately that's rarely the case.
 
I appreciate the offer but I'm in Canada. I tried to buy one this morning actually to compare against but it sold before I got to it so unfortunately for now I'm stuck with one.

I'm still trying to work out in my head the signal flow. I'm assuming as caius says the sound system is not running. The ym2151 doesn't appear to be getting data in from wherever it would normally come from. I will need to track those pins back to see where they originate.
 
brad808 said:
I appreciate the offer but I'm in Canada. I tried to buy one this morning actually to compare against but it sold before I got to it so unfortunately for now I'm stuck with one.

I'm still trying to work out in my head the signal flow. I'm assuming as caius says the sound system is not running. The ym2151 doesn't appear to be getting data in from wherever it would normally come from. I will need to track those pins back to see where they originate.
Click to expand...
Honestly I would start at the source:
- Is the sound CPU (V35) running? Reset, halt, clock signals, etc.
- Sound ROMs checked good against MAME romset?
- Healthy signals on sound RAM (one of the most probable culprit)
- TTL in between main CPU and sound CPU (used by sound ports to send commands to sound CPU)
- Etc.

Repairing board is a long process most of the time.
 
Thanks. I'm in no rush and hopefully learn more to fix other boards I have and just general broaden knowledge on it.


1) I have not been able to identify any pins on the sound cpu except the ones listed in mame source. NANAO 08J27261A1
Pin78 - 14.33mhz frequency
Pin79 - 14.33mhz frequency
Both those test good from what I see.

2) I've checked the sound ROM dumps against mame and get mt2 slo - 00c281a5
mt2 sho - 00c56e24 checksums which are clear against mame

3) I'm unsure where the sound RAM is. I'm thinking IC15 and IC16 SRAM cxk5864bsp-10l? Would seem obvious concidering location but I don't want to assume too much. I Will look up data sheet for these to see if I can identify which pins are which.

4) I'm also unsure where I would identify TTL Between sound cpu and main cpu. Is there any standard pinout for these (reset, haults, etc)?
 
Just to update this I am back at it. I have 2 full boardset now to help. I now confirm issue is on rom board by swapping sets. I have also double checked sound cpu by swapping and sound rom by swapping, all are good. I can certainly see differences on board at sound roms and sound rams with oscilliscope when comparing but unsure what I'm looking at still as I don't fully understand the logic yet.

wgWjiAZ.jpg
 
Yesterday I repaired an Hook ROM oard with missing sound.At the end it was due a broken trace somewhere in the sound CPU address circuit that caused crash of the whole system.So my advice is to look for missing signals.Are both ROM board from Major Title 2?Check also the PAL @IC7 as it's the address decoder for the sound CPU.
 
If you arent fully certain, try to piggyback the same TTL and Ram chips and see if there are any changes. The good point about this is that you can limit down what may be the issue if you have the parts available. If you do piggyback a chip and notice a difference, remove the chip, put in a socket and make note of it.

You will figure it out eventually :thumbup:
 
caius said:
Are both ROM board from Major Title 2?Check also the PAL @IC7 as it's the address decoder for the sound CPU.
Click to expand...
Yes both are major title 2. I also swapped ic7 pal and it is ok in working board.
 
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