Konami Simpsons - "The Simp"

[callanbrown]

This game was on location, and after about 6 months I was in and noticed some flickering graphics.

It seems that some portions of the sprite layer is not working. During the intro the "sons" is missing from The Simpsons but at the last few frames before it changes to the next screen, you can see the "sons" race across the screen. One of the eyes from each character is missing, and the diamond during the intro is barely there.

It passes all RAM tests on powerup and ROM tests in the test menu so I'm almost sure this is going to be a failing custom. I have already resoldered all customs so I don't think it's a solder issue. Board is super clean too.

I've attached a picture and here's a short video:

View: https://youtu.be/gbKqHD5_SGY

 

[callanbrown]

Tried replacing the 053251 custom since there was some evidence this had to do with layer priority, but no go. I did find that by shorting some address pins on the SRAM at 1J just below the sprite customs I could conjure the missing bits back to the screen (although causing other errors in the process). Piggybacking the RAM doesn't help and it passes the RAM test anyway so I think I'm going to just poke around the related chips. Would love it if it didn't involve replacing the customs!

 

[callanbrown]

Hmm, well while testing I found that if I bumped the voltage up to about 5.15 at the JAMMA edge everything comes back fine. Probably not a great sign for the future, but for now this board is 100% working!

 

[XtraSmiley]

As other's have recombined, op MAME up and mess around with different chips to see if you can replicate the problem, saving you time with real chips.

EDIT: You just posted before me, so now that it's a voltage issue, double check your PSU and also clean your JAMMA edge! Look for corrosion or trace damage from the edge.

 

[callanbrown]

As other's have recombined, op MAME up and mess around with different chips to see if you can replicate the problem, saving you time with real chips.

EDIT: You just posted before me, so now that it's a voltage issue, double check your PSU and also clean your JAMMA edge! Look for corrosion or trace damage from the edge.

Thanks, can you explain what you mean by "mess around with different chips" in MAME? I've heard of people injecting bad ROMs to see effects or poking around in memory, but if I'm expecting the customs to be bad, how can I affect that in MAME to test?

 

[XtraSmiley]

I don't think you can mess with the customs, I've seen people take about RAM chips mostly. I'm not expert though!

Also, 5.15v isn't a big issue, many PCBs run high or low, it's not that high.

 

[callanbrown]

I don't think you can mess with the customs, I've seen people take about RAM chips mostly. I'm not expert though!

Also, 5.15v isn't a big issue, many PCBs run high or low, it's not that high.

Yeah, for sure. It was just dumb of me because I saw it glitching in the arcade, brought it home and saw the exact same glitching and went right to chips. In fact the board I switched in at the arcade had been repaired semi-recently (

View: https://youtube.com/live/neQ6uf4uzY4
around 44 minutes in if you want to see that exciting repair).

 

[xga]

Hmm, well while testing I found that if I bumped the voltage up to about 5.15 at the JAMMA edge everything comes back fine. Probably not a great sign for the future, but for now this board is 100% working!

So if you have 5.15v at the JAMMA edge, what are you measuring on say a TTL IC somewhere on the board? My guess, is somewhere right around 5.00v with voltage drop.

 

[callanbrown]

Pretty much, 5.02V in the far corner. LS series chips are specced down to 4.75V VCC with a high logic level above 2V so one would actually expect the board to continue working at 4.8, 4.9 no problem. My other Simpsons board for example runs perfectly with 4.8 on the far chips.

This was a new problem for this board so something is definitely marginal and it will probably go at some point.