K7000 horizontal/vertical/pincushion? issue (sometimes)?

brandogg

Active member
Joined
Dec 16, 2023
Messages
186
Reaction score
53
I have a K7000 (probably a K7191, that's what most of my chassis seem to be, oddly enough) that every now and then will flicker and the image will squish after little horizontally, and stretch a little vertically (it also looks like it squeezes in like a pincushion effect). This usually lasts for maybe a second then goes back to normal, might happen every once in a while when I'm playing MKII. Earlier today it did the same thing but this time it did not correct itself, and then after a minute or two, I lost all picture. Rebooted, still no picture. I had to do some stuff so didn't mess with it, but maybe 30 min later or so I turned it on because I wanted to check for neck glow/raster, and it fired right up as if nothing was ever wrong. Any suggestions on what to look for, in addition to looking for cold solder joints? I did a full cap kit about a year ago and I *think* I did the flyback, but I may not have (haven't pulled the monitor to check yet). Attached a pic I snapled when the issue happened earlier, before the picture went away (just imagine a monitor that's not turned on for that case ;)), and then another when it was working as usually a bit after. Thanks!

Also one more note: the image did seem a bit darker when it did the squeeze/stretch thing, I think that comes off in the pic decently well, as if maybe the G2 was turned down - sorta makes me think flyback, but I'm not sure.
 

Attachments

  • 20250309_163032.jpg
    20250309_163032.jpg
    478.6 KB · Views: 16
  • 20250309_174155.jpg
    20250309_174155.jpg
    647.8 KB · Views: 16
Focus on the normal things, inspect solder joints for sure. Possible issues with vertical size pot or wires to remote board. Flyback issues are possible as the +24vdc for vertical drive comes from there. We really need to see the top/bottom side pics to be of help. There's a couple of recent threads here about vertical drive (collapse) even though your issue isn't collapse the information is pertinent.
 
Thank you. I'll look for those posts. I should hopefully get a chance to pull the chassis this weekend. I'm pretty sure I have an extra flyback, also ordered a filter cap since I was placing an order from APAR already.
 
Update on this: I think it may actually be my PCB? I did a cap kit on the sound board (since all the 90s Midway sound boards should be recapped), and because I noticed the audio was sounding a little scratchy. This didn't seem to make a difference in the end, and I noticed there is no startup tone (honestly can't even remember if MK2 has one). The game was playing blind though, and the audio seemed too kinda jump in midway (no pun intended) through the intro after one of the reboots. I popped in a Street Fighter II PCB and it's running perfect...no weird monitor resizing issues. Should I maybe recap the MK2 PCB? The board looks pretty great overall, and it is currently "working" but seems to have the screen flicker off very briefly and is currently doing the "sound doesnt work for the first minute or so" thing...any thoughts?
 
The amp heatsink is very hot too...guessing maybe that's my audio issues and not related to the video issue.
 
does the game ever just go black or not boot? one of the more common faults on T-unit hardware I've found is the +5V inductor by the JAMMA edge's solder just kind of disintegrates.
 
No that hasn't happened...I can't get audio to play at all now, but the amp is still warning up. Rechecked all my work for the caps and everything looks good, made sure the holes are filled from bottom to top, just like from the factory (a couple of the caps traces are on top of the board, but most are on the bottom). JAMMA edge looks very clean, too. The main board definitely has bowed in a little bit over the years but doesn't look cracked anywhere. I did notice that the 5V was pretty high (like 5.6V), but it's been like thay since I've had it, for about 15 months. I lowered it to about 5.1, no difference...wonder if years of being high may have caused damage though.
 
I think this actually is just two separate issues. I booted up SFII just now and it has no image (screen may flash static for a bit now and then, and it does show raster if I turn up the flyback) so hoping it's just the amp (about to order one) and then some other issue with the chassis.
 
So turns out the sync cable had come lose from the pin in the JAMMA harness, so it was likely just losing sync or grounding itself. I fixed that issue, replaced the AC filter cap, and replaced the power cable to the cabinet (ground had broken off) and now the monitor is working great...so I think that issue is resolved. Audio came on for a while but now it's stopped again...new amp on the way, hopefully that does the trick.
 
Ok, have not had the weird image distortion issue anymore, and I solved my audio issue as well (new amp), but here at about 18 seconds you can see the very quick flicker (see video below, right before the transition from Liu Kang/Shang Tsung to Shao Kahn/Shang Tsung). This happens every now and then. This chassis (P538) has all new caps, including the AC filter cap, new flyback, cleaned and re-greased anode cap. I do have to say that aside from that flicker, the screen is pretty GD crispy and the colors are incredible...but, any ideas on what to look at? When I redid the filter cap and anode cap grease I did a pretty good look-over of the chassis, didn't find any cold solder joints or anything, and it's not something I can recreate on demand by smacking the cabinet or tapping the chassis anyway.

 
Back
Top Bottom