Wells-Gardner 25K7193 monitor - Shaky/unstable

jfvary

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Hi all,

Please help me diagnose this problem. I have just purchased this MKII cabinet with a Wells-Gardner 25K7193. The picture looks good but is unstable and shaky. See this video. It difficult to see in the video but in person is is pretty obvious.

https://youtu.be/xv0W0wyO2BM

What do you guys think would be the problem? Cap, fly back, b+ voltage?

Thanks,

 
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had one of these, in an MK2 in fact.

half the solder joints were cracking at the flyback. the caps were original, it had almost every cap failure symptom you could think of (dark to bright, jailbars, overall shit image)

from about the middle of the chassis, starting at R101, going all the way to the voltage regulator, are a bunch of resistors that carry power from the other side (where R103, the standing resistor, is) ... it's totally not uncommon for these to have gotten hot enough over the years that they not only will crack the solder joints, but will also break the solder pads off. if you come across any where solder won't stick, the pad's gone. you'll have to sand or scrape open that trace and lay a jumper to the resistor leg. now would be a good time to cap the monitor, and the legs you cut off will make perfect jumpers.

basically, this is the "good reflow" method Buffett talks about a lot. in addition to all those power supply resistors, all ceramic resistors, and the flyback, you will also need to reflow the yoke plug and signal header. all of this coupled with new capacitors will give you a great monitor for many years. hopefully.
 
i agree with mecha caps and a good reflow to start. if you need parts i have them all including the best quality nichicon 105c caps in my kits.
 
A 'noisy' power supply can do tweaky things to your video. Can you rule that out by swapping power supplies or put the monitor in a different cab?
 
A 'noisy' power supply can do tweaky things to your video. Can you rule that out by swapping power supplies or put the monitor in a different cab?

this is valid too. K7000s just need a little more attention that many monitor makes in this regard.

what I've suggested is pretty simple. when that doesn't fix it is when you discover how ignorant K7000s can become. :p R101 and R103 are usually the biggest culprits, probably R89. I need to stock more replacements of these. C38 is another item that needs replacement a lot, that's the width cap.

if your HOT, flyback and C36(/C69) are all good then you just leave them alone. that includes white knob flybacks, the only instance you should ever replace a flyback on the K7000 is if it's noticeably cracked.

if you need power supply advice though, you can start at the PSU guide in my signature. I need to redo that thing soon, it's been too long now.
 
Thanks guys, I will take good notes of this, perform the check and report back. On thing I forgot to mention is that the monitor takes a while to start; it stays black for 10-15 sec before displaying any picture. Maybe there is a cue here...

I also have good news : the chassis in my Dynamo HS5 also host a 25K7193! This monitor is actually in great condition except there is a little "blooming" effect when there is a white flash on screen (for example when the Rareware logo flashes in the intro or when the lightning strikes in spinal stage). I'll have to investigate what is the cause of this.

Anyhow, this means I have a backup plan if I screw up and/or can choose the one with best picture quality for my KI cab! Anyway, I'll order two cap kits for both monitors and one flyback just in case.

I will create a resto/mod thread so you guys can follow.

Thanks again :-D
J-F
 
cap it and replace the flyback.

also on MKII specifically for some reason the complete image has a little wiggle to it.
i don't know if it is by design or a hardware issue of some type.

i have several MKII pcb's on my shelf and all of do that on any monitor i put them on. also the monitor in my dedicated MKII cab is fully rebuilt and has the same wiggle.
it is so subtle of a wiggle that most people never catch it.

you can watch the attract screen when the "press start" screen is playing, and you can see it wiggle.

using the same rig with any other PCB the image does not wiggle like that.

if you have another JAMMA PCB, try that in your MKII cab to see if the problem still happens before you do any work to the chassis.


Peace
Buffett
 
cap it and replace the flyback.

if you have another JAMMA PCB, try that in your MKII cab to see if the problem still happens before you do any work to the chassis.


Peace
Buffett

Ah, great info there. I'll try this before spending to much time to investigate.

Btw, I've watch your videos on youtube, they are great! Thanks!
 
don't be silly. Hantarex Polo has the best picture quality for Killer Instinct. ;)

the Midway T-unit just kinda sucks. I've never noticed MK2 having a wave in it by itself.

it's not like it does it in MAME.
 
don't be silly. Hantarex Polo has the best picture quality for Killer Instinct. ;)

the Midway T-unit just kinda sucks. I've never noticed MK2 having a wave in it by itself.

it's not like it does it in MAME.

that's because your the POLO master.:D
you eat and sleep POLO all the time.;)

need your POLO repaired send it to mecha.

every MKII i have ever seen not just in my collection has this issue.

MAME is different it runs on a totally different engine and the way the video is displayed it has a completely different engine driving it.

you can not replicate many of the quirks that OEM hardware has in MAME for most any game.

Peace
Buffett
 
Thanks guys! I've ordered a cap kit and will process with cap replcement shortly.

I've also found a diagnosis flowchart (googled "wg k7000 flowchart") and found out the B+ voltage may be the problem. Great info there...

I'll report back when the caps will be replaced
 
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