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MK2 - UB11 and UB13 failed, game stops

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mawrick

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Any tips on what might cause a mk2 board to stop on error with UB11 and UB13 failed, if this is memory related are these kinds of rams still obtainable new ?.

Also will it normaly stop the rest of diagnostic if this first ram test fails ?
 
mawrick said:
Any tips on what might cause a mk2 board to stop on error with UB11 and UB13 failed, if this is memory related are these kinds of rams still obtainable new ?.

Also will it normaly stop the rest of diagnostic if this first ram test fails ?
Click to expand...
by design, yes, they stop on the first error they detect. I don't know what a UB11 or UB13 are off hand, but a lot of the major not-74xx-TTL parts on these games are seemingly unobtanium.

like this is the only store I was able to find with what may be what is needed: https://www.pinballspareparts.com.au/electronics/memory/5340-13321-00.html

in other words you'll probably have to scalp ram off dead boards.
 
Does the MK2 boards boot without battery ?, and will it also boot without the soundboard/anything hooked up to it - only hooked up to a HAS Supergun ?.

I bought this board with the error mentioned, but after cleaning it and trying to boot it up nothing seem to happen, only 1 led lights up (I'v seen a couple of times the second led lights up for a brief moment).


Any tips on where to start troubleshooting would be appreciated :) (there is 5.1v at the jamma connector)
 
I see the 12v is just above 14V - could this potentially cause it to fail ? (and is there any dangers to it being that high) - not sure if it's due to the load being to low or what, but doesn't seem to regulate properly - it's a meanwell RT-125A psu, thought it have regulated to 12v earlier on, but been a while since I had it running
 
12V rail is usually only used for the last stage of audio amplification and most boards will boot if missing (a few exceptions are those late 70s/early 80s boards needing 12V for the CPU/RAM, so as -5V as well).
While 14V is a bit high it should be fine and won't stop the board from booting.
 
mawrick said:
I see the 12v is just above 14V - could this potentially cause it to fail ? (and is there any dangers to it being that high) - not sure if it's due to the load being to low or what, but doesn't seem to regulate properly - it's a meanwell RT-125A psu, thought it have regulated to 12v earlier on, but been a while since I had it running
Click to expand...
+12V has a wider operating tolerance. 10-14V is totally acceptable. +5V however is very narrow operating tolerance, 4.75-5.25V. don't try adjusting +5V to make -5V exactly -5.00V or +12V 12.00V, these are unregulated/unadjustable voltages and they're fine.

I don't think I've ever promoted this at AP, but I made this power supply guide years ago: https://www.arcaderepair.net/mechas-essential-power-supply-guide-remastered/

I was researching places to buy those video rams, I found like an obscure pinball supplier selling them. there's a possibility the UE13 Custom Chip has some popped legs from past board flexing causing the errors maybe.
 
@mecha, I would add a part for those early boards (late 70s/early 80s): they use CPUs and RAMs that absolutely need +5V, +12V and -5V for logic operation.
If any of those voltages is missing the chips die within minutes. Space Invaders is a good example, it's not rare I have to replace all 16 RAM chips.
 
Been probing a bit around and at the moment it seem like there is very high resistance between Max 691 (Vout pin) to UJ11 Vcc pin, the Vcc pin on UJ11 doesn't look to have a 5v level more of a 2v which also jumps around irratically......

Would it be safe to "jump" from Vout (Max 691) --> Vcc (UJ11), or something else that would be recommended.


btw, is the pcb more than 2 layers ? (realy couldnt see exact where this line goes....:) )
 
Ape Cosplay said:
For a quick test you can do it.
That said, are you sure the watchdog isn't barking?
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Not sure - how should the "watchdog" lines normally behave ? - what kind of activity is expected ?
(WDI of the 691 seem to sit at a constant "high" and the WDO seem to be sitting at constant low)

but should there be high resistance between those points mentioned ? (thought it went pretty much straight to Uj11 ?)
 
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also is it safe to pop in a CR2032 battery for testing ? (the BR that's in there is dead and I don't have a direct replacement either BR or CR versions)
 
tried probing vcc again and suddenly it show about 4V on uj11, not really sure that happened....:) (not much working though :) ) (it actually seem to be "jumping" a bit between roughly 3.5V and 3.75V periodically
 
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The board will not boot as long as WDO is low.
You have a short somewhere, first thing I'd check is for bent pins on the solder side, Midway liked to leave them sticking out by a lot, creating shorts.
 
mawrick said:
Any tips on what might cause a mk2 board to stop on error with UB11 and UB13 failed, if this is memory related are these kinds of rams still obtainable new ?.

Also will it normaly stop the rest of diagnostic if this first ram test fails ?
Click to expand...


Do UB11 and UB13 have a shared bus? If so it may not be those that have failed but something that it communicating with them

I've repaired several MK2 boards where there are bad traces from the VRAM to the CPU - check for corrosion and track damage before moving onto replacing
 
mawrick said:
Been probing a bit around and at the moment it seem like there is very high resistance between Max 691 (Vout pin) to UJ11 Vcc pin, the Vcc pin on UJ11 doesn't look to have a 5v level more of a 2v which also jumps around irratically......

Would it be safe to "jump" from Vout (Max 691) --> Vcc (UJ11), or something else that would be recommended.


btw, is the pcb more than 2 layers ? (realy couldnt see exact where this line goes....:) )
Click to expand...

It may have high resistance because it goes through a resistor or another IC on the way to that chip by design - is there a reason you are looking for the issue at UJ11 when the issue is related to UB11/UB13?

You are risking more damage by jumpering voltage to areas when you are not sure if this is related to the issue, the Vcc line may be low because it is being pulled low intentionally until a later stage of the boot process

There are also full schematics in the manual for MK2 as well which will make it much easier to troubleshoot :)

https://www.arcade-museum.com/manuals-videogames/M/MortalKombat2.pdf
 
xodaraP said:
It may have high resistance because it goes through a resistor or another IC on the way to that chip by design - is there a reason you are looking for the issue at UJ11 when the issue is related to UB11/UB13?

You are risking more damage by jumpering voltage to areas when you are not sure if this is related to the issue, the Vcc line may be low because it is being pulled low intentionally until a later stage of the boot process

There are also full schematics in the manual for MK2 as well which will make it much easier to troubleshoot :)

https://www.arcade-museum.com/manuals-videogames/M/MortalKombat2.pdf
Click to expand...

When I bought it the seller had it booting with the failure of UB11 and UB13, but after I got it, got it cleaned and tried to boot it it doesn't seem to boot at all, only black screen, no experience with these boards so no real reason for where I'm focusing :) - from what I read online the UJ11 is kinda a "common" failure if I'm not mistaken so was having a look in that area initially.

As it seem to be in watchdog mode I guess it also might be related to the 2 "program roms" ? (UJ12 and UG12) - I would think if those are "bad" it won't be able to boot at all - if I'm not mistaken...:)
 
Not really sure how/why but after I tried to do some probing on the main cpu (without screen turned on), I noticed there was suddenly a steady light on "activity LED" DS3. Turned on the monitor and seem to be back where it was as described when I bought it - so no longer a totally "dead" board. Feel free to chime in if there is any tips on further troubleshooting.

Is it normal that the card will "reset" itself like this one does when these errors are detected, or should it still go further before resetting back to the initial screen ?.







 
btw, is there any way to get it do do the additional checks on roms, kinda "continue" the testing ?
 
Try to set dip switches to disable the power-on test, and enable diag mode.

DIP 1 UJ1 - sw7 on - skip powerup test
DIP 2 UJ2 - sw8 on - diag mode

You should be able to enter diag mode i think.
 
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