Final Fight K7000 Monitor Problem

syplex

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K7000 Monitor Blowing Fuses (19K7901)

I picked up a Final Fight jamma cab which was working but had an intermittently working monitor. Sometimes it played blind, sometimes it came up with video. It had neck glow and I could turn up the brightness and see white on the screen. I also picked up a SF2 cab that had a completely black monitor that also played blind.

My friend and I replaced the flyback transformers and capped the monitor boards for both cabs last night. When I hooked it up it looked the same. Then after turning it on and of a few times the main fuse blew. I installed a new fuse and it blew that one, then I removed power to everything except the monitor and it powers up fine.

The monitor is a Wells Gardner 19K7901.

I installed a K7000 series cap kit and flyback I bought from twistedquarter.com.

The fuse on the video board is not blown. I have double checked cap polarities and looked for burn marks but didn't see any. What should I check next?

Another question, there is a green ground line running up to the coin door that has two more grounding forks connected to it that aren't connected to anything. I thought one should be connected to the video chassis since its not grounded anywhere else so I've had it connected there since I started on the cab. Where should those two extra points be screwed down? Control panel and video chassis?
 
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does the monitor come back on if you tap the monitor frame with like a screwdriver? the one thing you want to look for is neck glow, the orange glow that's in the CRT tube neck.

I had a problem like this in my Street Fighter cab where the monitor would periodically just fade to black and if you tapped the monitor frame, it would turn back on, and then it would go off again.

the problem in my case was the R213 (I think) resistor on the neckboard that goes to a circuit going to the neck socket (the white plastic part with 8 or 10 pins, depending) which is what's called the "heat circuit", this is what feeds the tube 'juice'. :) without it of course, you'll have no raster.

how did I fix it? I reflowed EVERY solder joint on the neckboard. mine's actually got a partial crack in it, which made it 10x harder to do, but I was able to get it. look for a lone resistor running along the side of the neckboard and follow the traces on it to see if they lead to the neck socket.

like I said, reflow everything.

otherwise... I don't know.

mine's a K7171. your mileage may vary.
 
I tested the bridge rectifier and it looks good, and the diodes D19-22 all read around 0.5 - 0.53.

But the HOT looks like it is shorted out. If I measure resistance from center lead to either of the other legs its zero. Where can I get a replacement? What would cause the HOT to go bad? Could playing with the pots like having H Hold too high/low cause it to go bad? What is a good safe level for these pots if troubleshooting, or does it matter? Can I disconnect the tube and power up the board to see if its blowing fuses (and if so what do I do with the flyback?
 
if the flyback took a shit, that'll blow the HOT too. I think the VR gets taken out on these as well, but if you say it meters fine, then maybe you're just out a HOT.

read the numbers on it and run a cross reference on http://www.nteinc.com/ with the numbers you see. this will give you an NTE replacement part #. then you can order from wherever you can find electronic components. I personally use Mouser (http://www.mouser.com/)

then you just do whatever needs to be done.. I'm sure you know how. :)

also I'm assuming this monitor requires an isolation transformer... or does it?
 
Yeah monitor requires an iso transformer, and there is one. This is an unmodified FF cab that was taken out of production many years ago then put in some guy's garage where I bought it from.

I just ordered a new HOT. Did I test the voltage regulator (STR3123) correctly?

Should the k7000 chassis be earth grounded, or grounded at all for that matter? Because it isn't currently.

Also the flyback transformer is brand new. It wasn't blowing fuses before I replaced the caps and flyback... why would it start now? I didn't test any parts before this so I don't know if the HOT was dead all along or not unfortunately. Is there a good troubleshooting guide for these?
 
yeah, all that's a bit out of my range. give it time though, I'm sure someone else will post here eventually.
 
I tested the bridge rectifier and it looks good, and the diodes D19-22 all read around 0.5 - 0.53.

But the HOT looks like it is shorted out. If I measure resistance from center lead to either of the other legs its zero. Where can I get a replacement? What would cause the HOT to go bad? Could playing with the pots like having H Hold too high/low cause it to go bad? What is a good safe level for these pots if troubleshooting, or does it matter? Can I disconnect the tube and power up the board to see if its blowing fuses (and if so what do I do with the flyback?


hots definately gone. best place to get is www.therealbobroberts.net hes the man..

playing with pots probhably didnt kill it, unless you messed with the hv shutdown pot.

it couldnt hurt to make sure none of the adjustment pots and cracked/broken ehile you are checking over everything.

if the hot is that smoked, most likely the vreg is also shot. CHeck c36 as those tend to shortout..

do not run thew thing without everything connected or you will just smoke more components.

I have one now thats going to get send to mod because i cant figure it out lol.. but check the most common stuff and usually you get lucky just replacing those things.
 
As for testing the voltage regulator - check for a short between pins 1 & 4. (two outermost pins)
H.O.T. should be checked with diode test not resistance.

And clarify exactly which fuse is blowing now ...... if it's the fuse I think you are describing then it "may" not be the monitor chassis at all. (if it's BEFORE the ISO transformer)
Fuse ----> ISO ----> Monitor
 
playing with pots probhably didnt kill it, unless you messed with the hv shutdown pot.

it couldnt hurt to make sure none of the adjustment pots and cracked/broken ehile you are checking over everything.

if the hot is that smoked, most likely the vreg is also shot. CHeck c36 as those tend to shortout..

Didnt touch the hv shutdown pot. Checked out all the pots tho they look good. I will check C36 next.

As for testing the voltage regulator - check for a short between pins 1 & 4. (two outermost pins)
H.O.T. should be checked with diode test not resistance.

And clarify exactly which fuse is blowing now ...... if it's the fuse I think you are describing then it "may" not be the monitor chassis at all. (if it's BEFORE the ISO transformer)
Fuse ----> ISO ----> Monitor

Diode tested the HOT and its shorted. The vreg is not shorted.

Yeah the fuse thats blowing is a fast acting 3 amp fuse thats in line with the power coming in from the wall before the iso. What might it be if its not the chassis?
 
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Yeah the fuse thats blowing is a fast acting 3 amp fuse thats in line with the power coming in from the wall before the iso. What might it be if its not the chassis?

Can you grab a pic of the setup in your cab ?
(easier for me to point out stuff in a picture)

Could be the ISO itself, could be a bad varistor on the EMI filter.
Point being that an "ISO" does just that, it "isolates" the monitor from direct AC.
So think of the iso as a dividing line..... fuses after the iso - monitor, fuses before the iso - AC power coming in.

Unplug the monitor from the ISO, does it still blow that fuse ?
Of course we could check components for shorts without wasting a bunch of fuses, but would need to see exactly what you had set up in there.
 
If the monitor is causing the cabinet fuse to blow, then capacitor C36 (the Critical Safety Capacitor) on the monitor main board underneath the flyback aluminum frame is shorted.

Also, a shorted marquee fluorescent ballast will blow the cabinet fuse.
 
Can you grab a pic of the setup in your cab ?
(easier for me to point out stuff in a picture)
Will do when I get home.

Could be the ISO itself, could be a bad varistor on the EMI filter.
Point being that an "ISO" does just that, it "isolates" the monitor from direct AC.
So think of the iso as a dividing line..... fuses after the iso - monitor, fuses before the iso - AC power coming in.

Unplug the monitor from the ISO, does it still blow that fuse ?
Of course we could check components for shorts without wasting a bunch of fuses, but would need to see exactly what you had set up in there.

When I unplug the monitor from the ISO (and leave everything else plugged in) it does NOT blow the fuse.

If the monitor is causing the cabinet fuse to blow, then capacitor C36 (the Critical Safety Capacitor) on the monitor main board underneath the flyback aluminum frame is shorted.

Also, a shorted marquee fluorescent ballast will blow the cabinet fuse.
The fluorescent light flickers quite a few times before turning on so maybe the ballast is on the way out. I will also check C36 when I get home.

Thanks guys.
 
Ok removed C36, it tested good and measures 6180 pF.

Voltage from the wall reads 120VAC and on the other side of the ISO (no load) reads 126VAC.

My current plan is to replace the HOT later this week when it arrives and see if that was the problem. Nothing else appears bad.

Should I replace C36 or the voltage regulator as a preventative measure?
 
Here's some pics of the cab. The second pic shows the fuse that's blowing. The green wire running up the left of the coin door is the ground wire I was asking about where it should be attached. The last two were disconnected and right now the 2nd one from the end is hanging on a control panel mounting screw.
 

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Ok removed C36, it tested good and measures 6180 pF.

Voltage from the wall reads 120VAC and on the other side of the ISO (no load) reads 126VAC.

My current plan is to replace the HOT later this week when it arrives and see if that was the problem. Nothing else appears bad.

Should I replace C36 or the voltage regulator as a preventative measure?

I don't know for sure, but I think under certain instances that you do replace them all.

the fuse that blows is the "line fuse", I'm not entirely sure why the monitor would make that fuse blow, and why the fuse on the monitor chassis wouldn't blow instead.

I'm sure the 120/126 is negligible, but maybe ISOs should be 1:1 with no margin of error like that. could be something stupid like the ISO not doing its job. did you try metering at the monitor power plug?
 
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C38 and D13 are good.

The replacement part I bought for the HOT is NTE2302. Will this work?

Any other parts I should check after I replace the HOT? Should I ground the monitor chassis or does it not matter?
 
NTE2302 should be fine.

You need to connect the black wire from the tube to the neckboard....
 
You're talking about the one thats wrapped around the tube (looks like for static discharge) right? I did connect that when I was having the fuse blowing problem.

Should the green ground wire in the pics be connected to the monitor chassis?
 
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