Mortal Kombat 2 - Repair And General Knowledge

[TheDeath]

Hey guys
A friend of mine sent me a non-working Mortal Kombat 2 PCB and i'm trying to repair it at the moment. I'm used to repair Konami/Data East boards but i've never worked on this hardware before so it's kind of a guess here.

Board boots up, i hear the typical williams tone but the screen keeps black and nothing change. LED on DS2 lights up, DS3 does nothing at all.

This board had minor works on it, it was kind of "hacked" 4MB version and there was some stacking on few 27c040. Jumpers were also set wrong to what the 4Mb or 8Mb version suggest to.

First thing i did was prepare the board for the 8MB set, set the jumpers and remove all of the 27c040 (they were also not covered on the window...)
PAL's were looking fishy, i replaced the A-16217 with a GAL22V10 and A-17748 with GAL16V8.

Then i changed the main eeprom cpu (UJ12 and UG12) for the same version. I wanted to burn the 27c801 set but i was out of stock, i ordered them.

From what i've read about this hardware, common failures are DRAMS and V-Blank circuit. Like many of these boards, mine came with 256 DRAMS with, cherry on top, FUJITSU brand... so i have ordered a new set since i do not have anything that could test these (even the mighty wonder NEOLOCH).

The V-BLANK circuit is generated by UD6 and UA4 and this could cause a lost of sync to the monitor. My boards was not display anything so i might thought that was the problem but i've piggyback them and tested, they were fine.

I was wondering if my missing sprite/backgrd eeproms and fujitsu drams are preventing this to even get to the boot screen.

Has any of you worked on this and might have some tips ?

 

[Geddon]

There is no knowledge that is not power.

 

[Hammy]

If UJ11 is toast the board won't boot.
You can cut uj11 out and the game will still run (it's the cmos chip). this is always my first shot.

As you correctly identified the ram at UJ4-7 are possible.

UG13, UH13, UJ13, UB18 & UB19 are common to go and cause corrupted cpu data lines.
Maybe check out the pal at UF17 also.

If your board gives the start up 'bong' with the sound board connected then it's time to check the sync / blanking signals.
Without the 'bong' it's a cpu issue.

Also check for dead short between +5v and ground..
if you do it's gonna be one of the surface mount rams.

 

[jassin000]

if you do it's gonna be one of the surface mount rams.

That ^ was what my board needed.
All the *creeking*cracking* sounds these boards make, I suspect lots of cold/busted solder joints.

 

[Hammy]

if you do it's gonna be one of the surface mount rams.

That ^ was what my board needed.All the *creeking*cracking* sounds these boards make, I suspect lots of cold/busted solder joints.

Yeah the V-ram on this is shit, but it won't cause the board not to boot unless it's dragging down the supply rails (seen this before)

The intermittent connections is what kills the chips, not only is the soldering shockingly bad on the midway stuff, the sockets and traces are not the best.

 

[ReplicaX]

if you do it's gonna be one of the surface mount rams.

That ^ was what my board needed.All the *creeking*cracking* sounds these boards make, I suspect lots of cold/busted solder joints.

Yeah the V-ram on this is shit, but it won't cause the board not to boot unless it's dragging down the supply rails (seen this before)
The intermittent connections is what kills the chips, not only is the soldering shockingly bad on the midway stuff, the sockets and traces are not the best.

Hammy hit the nail on the head. The most common repairs are generally poor connections due to crap soldering. Especially around chips, Eproms, and RAM. RAM sadly is usually the 1st to suffer and what I have mostly replaced on these boards, besides bad SRAM and crystals on the sound boards.

As far as the windows uncovered on the EPROMs, its common. The adhesive on whatever stickers they used literally turns to dust and they fall off.

 

[TheDeath]

Hey Guys, thank you very much for these usefull tips!
Suggesting what Hammy was saying, i removed the sram first and for a while DS3 was lighting very fast and i was able to see a tiny line that was scrolling horizontally, but nothing else changed (it actually went back the same after i tryed to reboot).

Since, still, i'm waiting for the dram and eeprom delivery, i pulled out allo of the Ls245 and 374 suggested. Unfortunatly i do not have a comparator that can handle 20pin stuff so i had to check them with my tla8866 programmer, they all tested good.

I have downloaded the schematics and i also checked if UD5 was good (i already checked UD6 and UA4, all good) since i saw this was handling the sync at the end of the circuit, it was also good.

I hope when i will get the drams to see at least the boot, meanwhile i will socket back these for possible future swaps if they are common to fail.

I also realized just now, there's a jumper that has not being mentioned during the 4mb/8mb mod, it's J18, above the UG12 eeprom. Since i have set the board for the 8MB version, what is the correct position for this one?

 

[Hammy]

 

[xodaraP]

I had the same issue on 2 of these. The PLCC socket the GPU sits in is a likely culprit. HSYNC and VSYNC are both generated there and combined by an AND logic. Start there.

The GPU on one of the ones I fixed had also died due to corrosion. The other one had a bad trace to one of the 245s I fixed up.

But if you’re not getting sync and you’ve checked the main boot ROMs, the GPU should be your next step.

 

[TheDeath]

Ha..
I went for the FPGA inspection, removed it (again), lifted some internal pins and socked it back but nothing was happening.
Then i was turning it on and off by touching it to see if i was able to feel some hot surface and this beast suddently boots, then it went black again.
I turned it on again without touching it, black screen. So i tought there was surely something not properly connected, i just went "wild" and start reflow any pin around the UF5 area and after a while i was finally able to let it boot properly.
I still missing eeproms but the worst is gone.
So it was basically shitty factory soldering job, even if they look good, they are not... I think the curplit was on the pull-up resistor array at RN12 (that is were the board finally keep booting at any power up after the reflow)

Fujitsu DRAMS are also ok 0_o that's a miracle!

 

[lukemorse1]

wow, those colors on the roms. I know the monitor is probably not degaussed but looks neat.

If only midway made error codes based on color combinations like if red and purple was ram failure and orange for cpu error whereas light yellow is a TTL issue

Glad to see it is showing some life again

 

[TheDeath]

wow, those colors on the roms. I know the monitor is probably not degaussed but looks neat.

If only midway made error codes based on color combinations like if red and purple was ram failure and orange for cpu error whereas light yellow is a TTL issue

Glad to see it is showing some life again

Hey Luke
Love your channel, i go back and forth from japan once in a year, i did also go to some of your hidden hard offs, that was fun

Yeah the monitor is not degaussed.. thats because my space isn't that much and so i have the solder pretty much underneath, going to interfere exacly on the right bottom.

 

[lukemorse1]

wow, those colors on the roms. I know the monitor is probably not degaussed but looks neat.

If only midway made error codes based on color combinations like if red and purple was ram failure and orange for cpu error whereas light yellow is a TTL issue

Glad to see it is showing some life again

Hey Luke Love your channel, i go back and forth from japan once in a year, i did also go to some of your hidden hard offs, that was fun

Yeah the monitor is not degaussed.. thats because my space isn't that much and so i have the solder pretty much underneath, going to interfere exacly on the right bottom.

Haha, thanks a lot man, that is some awesome stuff.
Yeah, good old Hard Off used to be really cheap and great deals everywhere. Now its kinda hit and miss.

Really good job on getting this far with the board as well. Looking good. Hope you get it all figured out soon

 

[ReplicaX]

If only midway made error codes based on color combinations like if red and purple was ram failure and orange for cpu error whereas light yellow is a TTL issue

Considering Midway actually had schematics in their manuals pretty consistent over the 80s and early 90s and a basic test screen. I will take those any day over fancy test functions. There are so many pcbs out there with literally nothing from other companies.

 

[TheDeath]

If only midway made error codes based on color combinations like if red and purple was ram failure and orange for cpu error whereas light yellow is a TTL issue

Considering Midway actually had schematics in their manuals pretty consistent over the 80s and early 90s and a basic test screen. I will take those any day over fancy test functions. There are so many pcbs out there with literally nothing from other companies.

They are also very detailed and clear to the eye! I repaired many Konami boards in these years and schematics are bullshit, unclear and sometimes also wrong (my topic on Mystic Warriors is the perfect example). I cannot believe that life-precise-people like japanese actually made those schematics...

wow, those colors on the roms. I know the monitor is probably not degaussed but looks neat.

If only midway made error codes based on color combinations like if red and purple was ram failure and orange for cpu error whereas light yellow is a TTL issue

Glad to see it is showing some life again

Hey Luke Love your channel, i go back and forth from japan once in a year, i did also go to some of your hidden hard offs, that was fun
Yeah the monitor is not degaussed.. thats because my space isn't that much and so i have the solder pretty much underneath, going to interfere exacly on the right bottom.

Haha, thanks a lot man, that is some awesome stuff.Yeah, good old Hard Off used to be really cheap and great deals everywhere. Now its kinda hit and miss.

Really good job on getting this far with the board as well. Looking good. Hope you get it all figured out soon

Yeah, they used to but nowdays even the "farest" one is allinied to what "akihabara" demands. Last few years they even got windowed shelfs for the expensive stuff!! I could not believe when i saw they got these!! I immidiatly thought "ok, the party is over even here..." they were also closing some of them... i had good times in Hachioji but now it's gone

 

[weirdal1968]

FWIW a friend's MK2 stopped working a few weeks ago. Would boot with one bong and a blank screen. One PCB LED was one steady and the other would flicker in a repetitive pattern. No sounds when coined up. 5V line was 5.1vdc at pcb.

Pulled boardset, cleaned all through hole socketed chip legs with no change in symptoms. Resoldered all through hole pins on the JAMMA connector side of the PCB. Didn't boot but I discovered a tiny solder bridge near the PLCC socket. Cleaned the board with alcohol, degreaser and water to remove all flux and waited 48 hours for it to dry.

Board now seems to work. Monitor went out so its playing blind but pretty sure the pcb is functional.