The Simpsons (Ongoing !) Repair *** NEARLY THERE ***

[TheDaddy]

So a slight update , I have pulled and tested 6G & 7G and both are ok. I have had a poke around and cant see anything obvious. I am unsure exactly how during a test the Audio reported to the main CPU that there is a issue. I need to look closer at the Schematics I suppose.

I do honestly hate Konami boards !! They are the wart on my arse they really are.

Dave.

 

[TheDaddy]

Does anyone have any ideas ?? I was on this for hours last night , and apart from , wrecking a trace I am getting no where. Just going round in circles and down the bloody rabbit hole. I spoke to Alice twice last night !!!



The audio is working , I have found 1 floating pin on a mask rom but apart from that nitto. I am unsure if its the Z80 or Main CPU that reports this fault, Without pulling every chip with an address line linked to the audio I am genuinely unsure where to go with this now. Obviously 6G and 7G and both absolutely fine , pulled and tested.

Thanks in advance,

Dave.

 

[yoganuggy]

Could be the same issue I had with a konami jackal. Bad YM3012 causing bad rom test

Sound on Jackal is generated by YM3012 and YM2151. Is that the same on simpsons?

On Jackal, the YM3012 and YM2151 talk to each other. YM3012 was bad and caused a funky clock on the scope that in turn caused bad roms on the rom test.

If you have a scope, measure the clock on the last pin on the YM2151. If the clock looks bad on scope, try take out the smaller YM3012 and then check the clock again on the YM2151. If the clock looks good replace the YM3012 and check again.

 

[TheDaddy]

Could be the same issue I had with a konami jackal. Bad YM3012 causing bad rom test

Sound on Jackal is generated by YM3012 and YM2151. Is that the same on simpsons?

On Jackal, the YM3012 and YM2151 talk to each other. YM3012 was bad and caused a funky clock on the scope that in turn caused bad roms on the rom test.

If you have a scope, measure the clock on the last pin on the YM2151. If the clock looks bad on scope, try take out the smaller YM3012 and then check the clock again on the YM2151. If the clock looks good replace the YM3012 and check again.

Ohhhhh very interesting , I did Piggy back the 3012 as I was aware it may cause the issue but was not 100%.

I will try testing and pulling them both tonight. I am assuming anything with a Dataline could be suspect ??

Thanks,

Dave.

 

[TheDaddy]

Both check out ok sadly 😥, i check the othe inputs / outputs abs seem fine as well.

Going have to start from the top and work down checking everything.

Tempted stick it on the 'Too hard' pile, draghing me down now.

Dave.

 

[Ace`]

Most likely bad Z80, YM2151, or 053260 custom. I had a Bucky 'o Hare that stumpted me for a while and it was the YM2151, it's just as likely to be the custom though. Golfing Greats is the best (cheapest) donor if it is the custom.

 

[TheDaddy]

Most likely bad Z80, YM2151, or 053260 custom. I had a Bucky 'o Hare that stumpted me for a while and it was the YM2151, it's just as likely to be the custom though. Golfing Greats is the best (cheapest) donor if it is the custom.

Thanks ace. I may pull the z80 and ym2151 and replace as hard to if they are good or bad rly.

This one is shafing me at the minute , i never get the easy ones. Just stuck a Gang Wars on the bench after a week of cleaning it. Not one fault but 3. Fixed palette ram , now audio and weird graphics issue to fix. No schematics either !

Dave.

 

[ktulu81]

any news on this? i've the same issue, try everything, i change the YM2151, check mask roms, audio eprom, check ram, clock, 74138, 7404, and change 053260 custom chip, and NOTHING! 🤬
🤬🤬

 

[Geekfix]

I had these errors for 6G & 7G absolutely no activity on Address/data from Z80, chopped it out, lifted pins and fitted a socket, ruining a good Z80 better than damaging the board. New Z80 fitted and alls well… Nearly, seems I’ve other issues now I’ve got past initial test

 

[TheDaddy]

Z80 was one on my list ....... It was a " Pull it and see " , But now you have said I reckon I need to. Not done anything on it for ages , I was having a dry spot and not been in there for many months sadly.

Dave.