Mortal Kombat, displays white line only

bigbadmiker

Member
Joined
Jan 1, 2010
Messages
421
Reaction score
0
Location
Washington
Hi, I'm new to the arcade stuff, so please forgive my ignorance. I just bought a Mortal Kombat dedicated cab from an auction. It was working fine the first day, but the next day I turned it on only discover a white horizontal line a couple inches from the bottom of the screen. It makes a high pitched sound when turned on, which I believe is the monitor making the noise. I hope this isn't a monitor problem. Could this be a power supply issue? I'm not seeing any lights on the MK circuit board, nor do I hear any game sounds. I also have a MK2 cab that I bought that works fine. Any advice and/or help is appreciated. Thanks and Happy New Year!
 
Hi,

Welcome to KLOV and the addiction of collecting games! :)

From what you describe I would say yes you probably have a power supply failure. If you can't get any game sounds when you try to coin it up and the led lights on the pcb are not lit then that definitely sounds like the power supply. Luckily they are easy to replace and inexpensive. The power supply probably has an led light on it also. Does it come on?
 
when transporting games, especially ones that have changed hands probably more than a few times, you have to check over the various connections inside the machine. I'm feeling kinda wordy right now: :)

JAMMA harness: this is the black connector that plugs into your game board. every input (such as your coin switches, your joysticks, and in the case of MK, the top 3 buttons, etc.), every output (such as the video signal that goes to your monitor, the sounds that play through the speakers, and on a very minimalistic level, the coin counters), and all the power wiring that comes off the power supply (for MK, this is +5V, +12V, -5V and of course the ground wires)

JAMMA harnesses usually go on pretty tight, but for the hell of it make sure that's on pretty good.

power supply: the power supply is powered by the 110-120V AC (your mileage may vary) feed that comes out of your wall outlet, and turns that into the various voltages I outlined above. MK uses a switching power supply (as opposed to what you'd find in a Pac-Man, Galaga, etc. -- those use linear power supplies, meaning they just have giant power supply boards set up to provide voltages). switching power supplies have a +5V adjustment knob on them, this is done because different games have different power needs. games with larger sets of interlocking boards for instance will need the power supply's +5V to be set a little higher to ensure that the game's getting a little bit over 5.05V to the circuitry -- if this is too low, then the game will malfunction. this is exhibited by a number of different factors, such as the game freezing up mid-play, or the graphics scrambling, or potentially in your case, not powering up at all. UNDERvoltage can be just as bad as OVERvoltage if you continue running the game under those conditions.

getting back on topic with MK though, MK has 2 boards: the main board, and a sound board. the sound board piggybacks its power off the main board, so generally I like getting about 5.10V at the JAMMA edge. if you know a thing or two about a digital voltmeter, it'd probably be in your best interest to check the +5 terminal to see what kind of +5 voltage you're getting at the power supply itself.

a thing to note about switching power supplies: only the +5V is regulated (via that adjustment pot) -- all the other voltages are "created" based on what you have +5 set at. it's not uncommon for the +12V for instance to run about 13.60V. :) also, under no circumstance in a working power supply will you ever have any other voltage besides +5 and have no +5.

that's enough about those.

the monitor: dedicated MK cabs shipped with isolation transformers, considering your monitor's turning on and all you're seeing is a white line, and the monitor didn't go KABOOM, I'm going to assume that you're getting 110-120VAC to it from the proper wiring to the iso. the other thing to check for is the video signal, which the actual connector's appearance varies from monitor to monitor, but what gets carried through this is the RGB signal (red, green, and blue are separated), a video ground, and then a video sync (MK uses what's called "composite sync", meaning the horizontal and vertical sync signals for the monitor are combined into one -- older games had them separate.) if under any circumstance your monitor (as in, the actual CRT tube) sounds like it comes on, and the glass neckboard is glowing an orange-like color (which now that I think about it, I don't think you can even see this in a MK/Midway cab!), and you can hear the game playing sounds, but you have a blank black screen, then it's most likely that your monitor is not receiving a video signal.

so.... I doubt the power supply would die mid-trip, my best guess is you should check the JAMMA harness that it's seated in good and tight. if that wasn't the problem, then next plan of attack should be the power supply -- perhaps a connection came loose (I'm going to assume this uses a screw terminal power supply, if it isn't, let us know!). actually, easiest approach would be to see if the power supply does in fact have an LED on it to see that it's even getting juice.

and welcome to this sadistic hobby! :)
 
Thanks for the information, guys. This forum rocks. Okay, so I checked the JAMMA connector, removed and reseated it, no change. So that's not it. I have a spare Happ power supply, so I think I'll try swapping that out next. One thing that I think is strange about the setup. The power cord goes to a box, wires then go to the power supply. Is the first box an isolation transformer (I think that's what it's called)? I've seen machines that just use a, ATX type power supply and a PC power cord plugs directly into it. I'm a PC tech, but this is so much more complicated than throwing a computer together. I'll let you know what happens with the power supply swap. Thanks!
 
is it like a big metal box with a brownish-orange shaped apparatus sticking out the top? :)
 
Yep. Then it's wired to a screw terminal Powermaster 1200 power supply. I don't see that it has leds on it. It's not as cool as the Happ power supply. I'm going to swap it out today, but have to spend some time with the wife first (so she doesn't kill me). I'll post this evening with results. Thanks, mecha187.
 
Post a picture of the image on the monitor. It sounds more like a monitor problem than a board one.
 
Post a picture of the image on the monitor. It sounds more like a monitor problem than a board one.

you would think, at first glance it sounds like vertical collapse. but he's saying there's no lit LEDs on the board, and no sounds (though MK1 DOES use a volume pot instead, perhaps it's turned all the way down?)

vertical collapse wouldn't appear 2 inches from the bottom would it?
 
f-ing righteous!

I'm impressed, you installed the new one right. :p (j/k)

I too, am a computer repair convert. I do this as my full-time job for my family's arcade... learned quite a few cool new tricks from the KLOVers here. good people, as per the closure of another forum I frequented, this one's my primary.

glad I could help out. I see an MK2 in the background... did you/are you going to complete the collection? I own all 4 game boards, trying to get my 33" showcase going.. then I'll be running probably UMK3 in it.
 
MK2 is one of my all time favorites. I played MK3 a few times, but I've never played MK4. I'll have to look into that, haha. I definately like your collection...KI cabs...awesome! My first arcade machine was a Street Fighter Alpha 3. I had it for a few years, but never had to do any repairs on it. I just sold it this past year, but I've always been a big Street Fighter fan. I wish we had arcades out here in California. They've all but disappeared, except for Dave and Busters and GameWorks. Thanks for the help...I'll be back!
 
yeah, my family bought a couple games off a guy that does tech work for us (the stuff I can't handle!) and the Tekken 3 was in a painted over KI cab, and the Street Fighter Alpha 2 was in a Pit Fighter cab. as much as I enjoyed both games, and was elated with having an arcade machine to play fighting games on again instead of MAME, it dawned on me one day that I could buy different JAMMA games for them.

I started with MK2, got reamed on it, paid $170, but I made some other cheap scores to offset it. then I got greedy one day, bought a KI board off ebay that was a 50/50 might work/might not. it didn't. and I'm quite certain the seller knew it too. I wound up restoring the Tekken 3 back to KI last year, I actually put blue T-mold on it last night to replace the worn/mangled original stuff. it actually has a purple appearance, but it said blue on the invoice I got from Happ, so whatever. I modeled this around KI2's primary color being "red", figure KI1 is blue...

I do most of my transactions on KLOV now, unless the boards/parts are explicitly labeled as being WORKING condition on ebay. I got a really good seller I've bought a lot of stuff from on there, he usually carries a lot of obscure shit too.

if you got any questions about some dos and don'ts, don't hesitate to ask. for what it's worth, this hobby's cost me $5000 now. :)

I ran out of room in my sig for my collection, so click my VAPS link if you wanna see the whole thing.
 
My collection...so far. I'll probably have to sell some of them...taking up too much garage space.


MK, MK2, SVC Chaos: Snk vs Capcom, Police Trainer, Lethal Enforcers (has issues), and a MAME cab I built this past year. Actually, all of these are from this past year.
 
Back
Top Bottom