Possible Broken Flyback. Could someone take a look?

[seven5]

Hey guys, I've got a Zenith 25" with a WG K7193 chassis. I've had my cabinet for about a month now and was just putting the final touches on my mame setup when disaster struck.

I was out running errands and my wife called to tell me that my cabinet made a loud hissing sound for about 30 seconds. She ran into my office and said the monitor had 3 lines on it full of static, then went black. After that there was a smell.

I had had my monitor on for about 10 hours today, but nothing on the screen, Windows' screen saver (blank screen) had been active.

From what I can gather from some quick research it sounds like maybe the flyback blew. I've read that the k7000 has a bad history with them.

I've attached a photo of the flyback hoping one of you more knowledgeable guys could help determine if the crack in the casing is indeed a problem or something that DID just happen. I have no clue if it was already there or not, its the only thing i can find wrong (not that I exactly know what I'm looking for).

If this isn't it, anyone have any other ideas what might have happened?

Thanks so much for your help guys.

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[lilshawn]

see this area right here on the gray wire where it's black:


your flyback is arcing out to your G1 lead.

just pull the wire off the flyback to the side and it will be good for a bit... but you should consider replacing it.

EDIT: yes it is a common thing with these flybacks. i ran a monitor a few months with a huge hole in the side... i just moved the wire till the machine came into the shop for service.

[seven5]

I pulled the gray wire off and put it to the side and no luck. I've got a black monitor, and no neck glow.

[lilshawn]

the flyback may have popped...as well as the HOT and possibly the B+ regulator.

looks like you might have some parts to order.

check the HOT with a multimeter. set it to ohms measurement. place a lead on the the middle leg and place the other on either one of the outside legs... it should read open or very high resistance... if it reads as a short or low resistance, it's popped.

if the HOT is popped, replace the flyback and the HOT and see if it comes up, if it doesn't you have some B+ issues.

it may be easier to find a TV repair shop to fix it for you if you don't know much about soldering.

[seven5]

Thanks!

After a ton of research tonight I've come to that conclusion as well. I'm actually in the middle of putting my order in to Bob Roberts as we speak to get the Flyback repair kit which has the hot and a cap kit. I figured if i was going to order, I'd get my monitors first aid kit while I was at it. And since it'll be out of the cabinet, might as well do a cap kit.

Luckily i've got a k7000 and not a k7000a. I was a little worried at first!

Thanks for your help!

[boardjunkie]

Holy hell....thats a pretty good f-back meltdown. Whenever you see even a small crack in the casing of a f-back, its junk for sure. Don't even screw with it....just replace it. And you'll have to replace the horiz output transistor as well. The 7000s used IC b+ regs, so its possible that got taken out as well. They are nowhere near as robust as a discrete reg with a to-3 case pass x-istor.

[lilshawn]

if caught soon enough, it could have been saved... but letting it go for even 20 or 30 seconds is enough to cook everything nice and hot.

cracked flybacks are extremely common...especially the 7000 series. they run really hot, and thus, crack the plastic case. stuff starts warping, oxidizing... then failure.

[seven5]

Thanks guys, I got the kit from Bob Roberts today and plan on replacing soon.

Does anyone have any tips for me before I start?

Also, I know i need to use thermal paste for the HOT, but can I use ceramic-based thermal compound? I have some of that around the house already.

Thanks!

[grantspain]

use solder wick

[seven5]

I've got it ready!

[lilshawn]

Also, I know i need to use thermal paste for the HOT, but can I use ceramic-based thermal compound? I have some of that around the house already.

should be fine... be sure if there was a mica or silicone insulator on the original HOT to carefully clean and re-use it, otherwise the HOT will short out by being grounded to the heatsink

[seven5]

Ok, I got the new flyback put on and the new HOT installed and everything starts up again!

I tested the B+, the voltage regulator, and r301, amongst other things, and everything looked good. Hearing that static sound when I hit the power button was music to my ears.

The only problem now is that my picture is pretty blurry. I messed with pots all night and I could get real close to a good picture but now like it was before. I could get it sharp, but not bright. The second I turned up the brightness, the picture got blurry.

Here's whats interesting, the focus pot on the new flyback doesn't seem to affect anything. The picture doesn't change at all. And the screen pot seems to be VERY sensitive, more so than it was on the old flyback. I can get the picture really close to looking right except its pretty blurry, it feels like all it'd really need is a little tweak of the focus pot and it'd be fixed, but the focus pot doesn't seem to affect anything.

Has anyone seen anything like this before?

Thanks guys! Almost there!

[lilshawn]

you did remember to hook up the focus wire right?

[seven5]

I did. I had to snip it of course to swap out the flyback. Instead of using a butt connector, I just soldered the two wires together and wrapped them in electrical tape. I wiggled the connection and didn't notice any difference.

[lilshawn]

Hmm. Not sure... Maybe the flyback is a dud? Send off an e-mail to the store you purchased it from... Let them know the focus pot doesn't seem to work. Maybe they can offer a suggestion or maybe ship you another.

[seven5]

I got it from bob roberts. I'll do that today, I just wanted to hit up the forum before I bothered him.

Thanks!

[seven5]

Boo ya! I got it working. The problem was that I spliced the wires from the new flyback to the neckboard wires. It doesn't like that.

I figured out that the one wire comes out of the plastic piece by just flipping it up. Once I did that I plugged the wire from the new flyback into it. Then the wire that attached via a little plug I just pulled off and soldered the new on directly to the pin. It was spliced only about 4" up, but it wasn't good enough.

Once I did this my screen and focus pots were in full effect.

I'm having a bit of a problem with the width though. Its a little too wide. I tried adjusting my horizontal width coil but it doesn't seem to be doing anything. I spun it both ways. One way it practically starts unscrewing. The other way it just stops. Am I mistaken with how to adjust it? Could it be bad?

[lilshawn]

Boo ya! I got it working. The problem was that I spliced the wires from the new flyback to the neckboard wires. It doesn't like that.

I figured out that the one wire comes out of the plastic piece by just flipping it up. Once I did that I plugged the wire from the new flyback into it. Then the wire that attached via a little plug I just pulled off and soldered the new on directly to the pin. It was spliced only about 4" up, but it wasn't good enough.

yeh, high voltage is really temperamental when it comes to resistance. with such high voltage, you don't get much currant. it's currant that does the pushing. if there is resistance of extra wire...it may only be a few tenths of an ohm, but it looks like it was enough to throw off the focus.

I'm having a bit of a problem with the width though. Its a little too wide. I tried adjusting my horizontal width coil but it doesn't seem to be doing anything. I spun it both ways. One way it practically starts unscrewing. The other way it just stops. Am I mistaken with how to adjust it? Could it be bad?

have you replaced any of the caps on the board? it might be time for a capkit... if your horizontal still wont squeeze down with pot tweaking, there is some caps that cause it to stretch way out and the pot seems to do nothing..

[seven5]

I can take a look. I got a capkit when i ordered. But to be honest, a lot of the caps on this board look fresh. I think it's had one recently. But i'll investigate other caps that would do this.

Thanks!

[lilshawn]

I can take a look. I got a capkit when i ordered. But to be honest, a lot of the caps on this board look fresh. I think it's had one recently. But i'll investigate other caps that would do this.

Thanks!

caps aren't always obvious when they go bad. sometimes the top will bubble out and it's a dead giveaway, but others won't show at all. Mainly  the ones that don't show, the rubber seal at the bottom dries out and shrinks a bit, then the electrolyte evaporates out laving a nice looking cap, but non-functioning.