Monitor shut off and burning smell. WG25k7193

[dougman]

My WellsGardner25k7193 monitor was on, and then all of a sudden, i heard a weird electrical noise and the monitor went blank and then i smelled something burning.

The tube no longer glows in the back, and the fuses seem fine.
Is there an easy fix for this?  I just bought this machine less than a month ago used.

I don't know where to start.

[Ken Layton]

The flyback just died.

[dougman]

the flyback?
a $70 replacement part...
Easy fix? direct replacement? Can it bring up more problems if I do it myself? 
Anyone in Vancouver BC want to come and fix it for me? I don't want to pay hundreds of dollars to get it fixed.
Are there service manuals somewhere for these monitors?

Is there a good arcade monitor primer I can read somewhere?  I am good with general electronics but I haven't dabbled into monitors. 

[Ken Layton]

Visit this site to learn more about your monitor:
www.jstookey.com/arcade/WG_25k7191/

The original flyback on this series (k7000 series, of which yours is part of) is a high failure item. It is frequently on sale at places like www.penn-ray.com for $15. The usual price of this flyback is around $30.

John's Jukes (www.flippers.com) is located in Vancouver BC. They repair video games, monitors, jukeboxes, and pinball machines. They know their stuff and prices are reasonable. I suggest you take the whole monitor to them for repair.

[Hiub1]

Ken, you just answered a question of mine about a WG25k7195 being part of the  K7000 family. Would that flyback be the same model? The problem I am having is that the monitor will turn on for a fraction of a second, and then turn off. I wasn't able to find a lot of information on this monitor or a similar problem. Sound familiar to you?

Thanks in advanced, Fred.

[SirPeale]

The problem I am having is that the monitor will turn on for a fraction of a second, and then turn off.

B+ voltage too high?  Measure and adjust if necessary.

[Ken Layton]

If after doing a capkit the monitor still shuts down then the voltage regulator should be replaced.

Yes the flybacks for the k7000 and k719x are exactly the same. Bob Roberts, Zanen Electronics, and Penn-Ray all sell it. Penn-Ray (www.penn-ray.com) usually has it on sale.

[Hiub1]

Thanks for the help guys, I have a cap kit on the way, and I will measure and adjust B+ voltage to see if that fixes anything.

Once again, you guys are great!

[dougman]

Dammit,
I replaced the flyback, HOT, and fuse, and when i turn it on, burnt smell again, and i watched the back, and it looks like the HOT (2SD1398) is sparking.

What could the problem be?

[grantspain]

a hot sparking is wierd,has it exploded in the middle,have you changed it before,is it a plastic package or does it have a metal back,did you put plenty of heat conductive grease on the back before fitting it,if its a metal back is there an insulation sheet behind it,is ther anything else sparking to the frame?

[dougman]

the original hot didnt look burnt up.
it is a metal backed transistor and it had an insulation sheet behind it.
it was kinda making fizzy sounds and glowing/sparking orange around the edges.

should i try another HOT?
:/

maybe i should get a chassis replacement and save myself the grief.

[grantspain]

i think your hot is shot and the insulation sheet is damaged-try replacing them first(make sure you use heat conductive grease)-its cheaper than replacing the chassis and your gaining valuable knowledge(thats priceless)

[Ken Layton]

The horizontal output transistor must have a fresh mica insulator between it and the metal frame. That insulator must also be coated on both sides with silicone heat sink grease (light film of it). Reusing the old insulator is not a good idea as the old one may have a pinhole in it.

When you replaced  the horizontal output transistor, did you remember to trim the excess leads so they don't short circuit to the metal chassis?

Other possible causes of your problems could be shorted capacitor C36 (the safety one mentioned on Bob Roberts' site) and damper diode D18 (next to the yoke connector pins on the main monitor board)..

[dougman]

replaced the HOT again, and the mica, and fuse.  Now i turn it on, and nothing happens.
no glow. At least there is no burning smell. heh

I think I will just replace the chassis. I am getting really frustrated. 
I think I will order the 825H from Alva amusments... And if this doesnt work, I am going to be really sad. 

edit, looks like im burning up fuses. and now a burning smell......
I hope the tube is ok. There is no way to burn out the tube like that right?

[SirPeale]

If you're blowing fuses, check out the four diodes in the power supply section of the board.  One or more is likely bad.

[cool_guy]

I have fixed MANY K7000 series chassis's. First off 99 out of a hundred times, the flyback will throw cool/scary lightning when it fails. There is ALWAYS a visible burn mark on the flyback somewhere. If the monitor doesn't have a ground hooked up usually that "lightning" will find ground via the video signal and annihilate your game board. 50 percent of the time the chassis is perfectly fine with a mere flyback replacement. Sometimes It wipes out the voltage regulator as well STR30130 (25") and STR3130 (19" I think. all 25" k7000's flybacks are interchangeable except the really old ones that are made by Zenith. The Zenith model is a very easy to identify because the flyback has "ribs" around it and is usually green or tan.
C57 is always a good cap to replace if you have it and are soldering. 160volt 47mfd I think. When flyback work is being done its good cheap insurance to replace the three caps in the direct vicinity of the flyback. If all else fails check the funky four legged bi-polar cap between the flyback and heatsink. When this cap is bad the H.O.T traces will appear shorted even with the H.O.T removed.
The k7000 is a rugged chassis and usually fairly easy to repair. Have fun, good luck, and don't get dead.

[cool_guy]

definately no way to burn up the tube. I agree fully about the possibility of a bad diode causing a blown fuse. @ this point I would say obtain Randy Fromm's flow chart for this chassis as none of us are able to physically look at your chassis. How are you testing this chassis?? Is it Isolated?? This Chassis must be isolated. I blew up a couple by accident in the early days of my learning curve by not isolating. What if any measurements were you able to obtain?? If there is a burning smell than something HAS to be shorted. leave no stone un-turned. The chassis does not have tons of parts. It should't take but 15 or 20 minutes to check every diode and transistor. I forgot to mention in my last reply, that funny four legged cap is not on all chassis. at some point W.G changed to two seperate caps side by side and I have never seen those short. If you have it, you will see it, if not, lucky you. I will be doing much k7000 work in the next week or so as I have about 6 that have rolled over and no more spares. If I find anything similar I will post again.

[dougman]

Ok, I guess I will check over all the parts again.  I don't have much equipment to test everything, since all I have is a multimeter. :/

Here is a pic of the board from the original incident. I actually didn't see anything look burned. The original Flyback looks fine and dandy too.

[grantspain]

a mulimeter is all you need,don't give up,does the fuse blow directly on power up?if it did not do it before you changed the hot then check for solder blobs or track problems,or maybe you crushed a wire refitting the chassis,try disconnecting your degauss coil first,and like peale said check out any diodes on the primary power circuit

[SirPeale]

I can't tell from the pic, but is that a bridge in the upper left hand corner?

[cool_guy]

the bridge is in the upper right hand corner next to that giant black cap. The upper left corner is where B+ measurements are done. One side of the giant ceramic resistor is B+ and the other side is called "raw" B+. Raw B+ is always higher as it has not passed through the resistor yet. Test by metering DC voltage, one lead on the heatsink and the other on the resistor.

[SirPeale]

So it's not a bridge rectifier (one piece unit) it's four diodes acting as one.  Gotcha.

See, this is why the boss pays you the big bucks.