Golden Axe with faulty sprites repair log

[pacoarcade]

Got this golden axe with wrong sprites. My first thought was faulty custom chip or faulty rams so I ran the tests but it showed GOOD. Since this is not conclusive I used a working B board with this A board and I was happy to check that it worked flawlessly, whoohoo!

Then I extracted B1...B3 and B4...B7 roms (27C020) and compared MD5 checksum against the mame set. B2 and B7 were bad, so I burned new eproms:

• mpr-12380.ic10 for B2
• mpr-12383.ic14 for B7

It fully fixed the problem. Repair done!

 

[Darksoft]

That was really good luck. Have fun!

 

[Apocalypse]

Sega custom chips, especially THT are probably the most reliable to me.
Mask ROMs however are generally terrible.

 

[pacoarcade]

To complete the repair I replaced the other mask roms since they had some rust in their legs. I used 27C020 for B1...B3, B5...B7, 27C301 (non JEDEC) for A11 and no jumper change. I suppose brand new AT27C020 OTP eproms are an option as well as a modern replacement for old ceramic 27C020. Is there any modern replacement for 27C301?

I wonder if a mask rom failure may cause other faults in the board, do they tend to short? or they just simply start putting out wrong data? I have the same doubt about the Fujitsu TTL chips. I got some faulty Fujitsu EPROMS that triggered the overcurrent protection in my programmer.

I also did a full recap using Panasonic NHG and Rubycon PX from Farnell and the good ole Kester 44 solder wire. It's tempting to use long life low ESR caps such as Panasonic FC, but I prefer to stick to the same kind of capacitors since I have experienced problems replacing GP caps with low ESR ones (Panasonic FR in particupar) in the Sega Mega Drive. Now I'm stocking Rubycon YXM, automotive caps rated for ~12.000h at full ripple 105ºC and not low ESR.

All the Sankyo 470uF of the base board were way out of spec along with some others of different brands. There was two or three Rubycon CE caps that were ok, but I replaced them anyway.

I have found that Hakko N61-07 tip is really nice to remove capacitors on arcade boards. In order to remove the 0.1F supercap on these boards (for example if you need to clean) a 1mm tip is needed (N61-0.

 

[pacoarcade]

After some hours playing the game it developed another issue. Suddenly, the screen was 50% white:



After one minute it turned even worse:



I restarted the game and the sprites issue appeared again:





Swapping boards I came to the conclusion that the A board was the culprit. I extracted ram chips at F2, F3, F4, F5, H6, H7, some tested bad in my Minipro. Then I installed dual-wipe sockets and new ram... it worked better, but there were still some blinking issues.

Then I installed new ram modules of the same brand and same speed and now it works fine again!

 

[Apocalypse]

I extracted ram chips at F2, F3, F4, F5, H6, H7, some tested bad in my Minipro.

Why didn't you pull only the faulty ones?
How many were actually faulty?
It would be weird for all of them to fail at the same time, however when working in pair you can expect both to go bad at very close interval.

 

[pacoarcade]

Because they were all sony. Lately I've found they're probably the most failure prone ram chips in arcade boards, so I prefer to repair just once and be done with it. Two or three of them didn't pass the TL866A tests.

I've used MCM2018AN45 as a replacement, in my experience they are pretty reliable.

 

[Apocalypse]

Ah ah, the most failure prone RAM chips are the "shiny" ones (usually either Toshiba or Sony brand).
But the matt ones from Sony are pretty bad too (CXK***).
I've found Cypress or ISSI equivalents are very good.

 

[pacoarcade]

The only modern 6116 static ram I can find at reliable sources is 6116LA20TPG at Mouser. They're made by IDT.

 

[Apocalypse]

I've bought a lot of CY7C128 few years ago, datecode was definitely past 2010, probably not manufactured anymore but still were relatively recently and I'm pretty sure there are plenty of stocks.