Mortal Kombat II reset BING / BEEP out of nowhere?

Mike Valmike

Well-known member

Donor 2012, 2014
Joined
Aug 19, 2012
Messages
1,577
Reaction score
26
Location
Arizona
I recently rebuilt a dedicated MKII (pics coming when I treat the sides in an attempt to get the sideart to survive its entombment under black paint) and for the most part it is working well. I am still getting some monitor flagging at the tippy top no matter what I do to the frequency POT and horizontal hold, but I'll figure that out eventually and the players in my arcade don't care because the distortion is only visible up above the life bars where nobody looks. However, they DO care that every once in a while the system emits its huge BING / BEEP as though it had just been rebooted. Some of them are reluctant to play, thinking it will reset mid-game. So far this has not occurred when it was coined up, only in attract mode. And the motherboard didn't actually reset. That's the weird part. The attract mode continued unchanged. But that BING is hard to miss, and it happened again an arbitrary number of hours later. Anyone ever heard of this? Perhaps I've hooked something up wrong? Is it going to reset if there's a game going on, you think?
 
Ahhh the Midway BING!!! At least when you start up the game you can prepare for it. I can only imagine how much it would suck to not know If and when that noise is going to happen. As for your issue I've heard that mk2 boards can be real finnicky about the voltage so I would check your power supply.
 
yup definitely check your voltages (+5v and -5v), as for your fold over at the top try adjusting your vertical size pot now that you've messed with the 50/60
 
more like a BONG! sound. lol. that sounds to me like power is getting interrupted to the sound board somehow. the +5 (driving the sound hardware), not the +12 (for the actual amp).

as for "finnicky" voltages, I would be more inclined to say your +5 is set too low. it's enough for the main board, but once it crosses the wiring harness to the sound board, it might be a bit diluted by time it reaches there.

it's relatively easy to check the voltage going to the sound board however, by way of the P1 header on it that the wiring harness plugs into. make note of the numbers on the header, one side will say 1 and the other 9. pin 8 is +5, pin 9 is ground, stick your red meter probe in the +5 side and black probe in the ground, with meter set to 20 VDC range. if it's noticeably low, don't go turning the adjustment knob on the power supply just yet.

like most of these boards now after nearly 20 years of use, the JAMMA edge connectors can get dirty, and the more dirt and gunk that forms on the contacts, the harder it is for the power to efficiently get through. remove the main board and get out one of those pink erasers and vigorously rub at the contacts of the JAMMA edge going up and down on each contact and then going side to side across the whole thing. wipe _all_ the eraser fragments off the board. if you wanna get real intensive with cleaning, 91% isopropyl alcohol and a paper towel has worked fairly effective for me. give it a few to dry (it evaporates fast) then reinstall the board and reconnect the sound board wiring harness, ribbon cable and kick harness and try metering the sound board again.

if all goes to plan, you should see an increase in the voltage. once you're all done testing, leave the probes plugged in and gradually step up the +5 via the power supply's adjustment knob until you get 5.10V at the sound board header. this will allot you plenty of voltage, and it will be within means of safe operation. your power supply will operate more efficiently (the dirty edge connector will result in an increase in current, which can over time damage the connects where power is supplied to the game board) and it should eliminate your BING or BONG problem entirely.

if this somehow doesn't get it, next bet would probably be to reflow the header pins on both the main and sound boards.

EDIT: for reference: http://arcarc.xmission.com/PDF_Arca...rtal_Kombat_2_Kit_(16-44029-101 Oct 1993).pdf slide over to section 3-2 for the wiring info.
 
Last edited:
Update: Voltage at the source is 5.30v, voltage coming off the sound board pinout on the main board is 5.30v, voltage at the sound board is 5.27v. That's not too much loss, is it? Conversely, am I running too "hot" and in danger of frying my hardware?

Thanks much for all this guidance gentlemen, your advice on how to approach it has been spot on


EDIT: Also, fixed the monitor, there was a thread for that under monitors too. Turns out the pinout I was given was wrong, and I had the sync wire plugged into an unused pin. One of the guys who replied had the correct pinout. I put the sync in the correct place and the image is ABSOLUTELY GORGEOUS could hardly be more perfect.
 
Last edited:
try and shoot between 5.10 and 5.20

glad you got the monitor sorted out, good to know about the sync wire causing that issue.
 
definitely turn the voltage down. I don't think 5.30 is high enough to damage anything though... at least I don't think.
 
Back
Top Bottom