WG K7000 series dead. WWYD?

shardian

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I just got 2 games that both have 19" WG K7900 monitors. One needs a cap kit, and the other seems 100% dead. IE, no monitor glow, or snap/sizzle when powered.

For the dead one, what does it mean if absolutely nothing happens when turned on? HOT is dead? Flyback is dead? Board dead?

Nothing looks obviously burned. I am considering getting a Bob Roberts deluxe rebuild kit. I really am not familiar with the functionality of the HOT. Am I wasting my money on this, or is there a good possibility it will work after the rebuild?
 
Check the fuse by the flyback if it's blown then at least you know where to start. The deluxe rebuild kit will take care of most issues if not all.
 
#1 check fuse AND fuse holder. They get weak and someetimes the tang will fall off.

If the fuse is blown:
check the hot. Its the large transistor. Ohm between pins #2 and 3. If you read anywhere near 0 ohms, its shorted out.....
Most likely due to bad fly..
also check the large diodes(rectifying diodes). Sometimes those short out.

If the diodes check ok, replace the fly, hot, voltage regulator, fuse and recheck.(sometimes you dont need a vreg but for a newb just replace it and do yourself the favor or not having more guesswork)

Now..

if the fuse is not blown: first off make sure shes gettin 110vac. check that fuse holder. check the hot.
check it over well for bad solder joints. These get krappy solder connections all the time around the r98-r101/flyback/yoke area of the board. Actually desolder r101 and reflow regardless. SOmetimes that trace tarnishes black and you wont see untill you desolder it. Repair as needed.
Recheck- still no joy? Replace the 2 caps right next to the hv shutdown pot. I have actually seen just those caps get krappy and cause shotdown. Obisusly if that fixes it, you need to pull it and do all the caps too!



lets go form there. Thats how i usually attack the k7000's. Im not saying its the "right way" but thats the method ive come up with and 98% of the time i get them going again
 
Also, if you look closely at the K7000 flyback controls, you'll sometimes see tiny cracks around them. They can cause a short inside the flyback.

Obviously check the fuse. New caps are a given. If your HOT is bad, check the four-legged safety critical cap behind it.

Also, check the AC coming into the power connector. the VR is rated for 130v, so if you're iso is pumping out 135v....
 
Also, if you look closely at the K7000 flyback controls, you'll sometimes see tiny cracks around them. They can cause a short inside the flyback.

Obviously check the fuse. New caps are a given. If your HOT is bad, check the four-legged safety critical cap behind it.

Also, check the AC coming into the power connector. the VR is rated for 130v, so if you're iso is pumping out 135v....

THANKS MOD...man, almost forgot, them flybacks on these suck and develop cracks over time.
If your fly has white adjustment knobs, REPLACE IT NOW.. those tend to puke more then thier counterpart with the black adjustment knobs for some reason...
 
man im slipping today..

add to this:

if fuse is blown: ohm between each end of c36. Sometimes those short out, take out the hot, vreg, and, anf fuse..

the allso willl sometimes go if the fly goes


These are kind of presnickity but with a little patience they can usually be resurrected easily. Alot of people complain about the k7000 but around where i lived in chicago,l thats all i messed with.. so to me at least, they seem easier to fix than the competitors monitors...
 
If your HOT is bad, check the four-legged safety critical cap behind it.

man im slipping today..

add to this:

if fuse is blown: ohm between each end of c36. Sometimes those short out, take out the hot, vreg, and, anf fuse..

they also willl sometimes go if the fly goes

Same advice, just with a part designator...
 
I poked around on this monitor last night, but forgot to bring this thread and a manual home with me.

Anyways, the fuse and holder tested good. I tested what I assume is the HOT (It looks weird compared to the standard looking one on a G07) and got around 25 ohms. This of course assumes I tested it right. I then took it out and gave it a good bath. It looks brand new again. :D I looked it over real good, and didn't see any burned areas. The flyback does indeed have white controls.
 
pull the hot, and ohm it again.. if pins 2+3 still read 25 ohms, that hot is shorted.

You need to replace that flyback regardlessly... those white knob ones fall apart!

Id ohm out that c36 cap and see what it reads too...

in any case, sounds like your gonna need a hot, fly, mabye c36 and mabye a voltage regulator... if caps look old nows the time to do those too...
 
I just got 2 games that both have 19" WG K7900 monitors. One needs a cap kit, and the other seems 100% dead. IE, no monitor glow, or snap/sizzle when powered.

Am I wasting my money on this, or is there a good possibility it will work after the rebuild?

Before I would drop any money on parts, find out if the second tube is working.

I would take the chassis that semi-works and plug it into the tube that looks dead. If the tube is cracked or otherwise blown it will still not come up with the other chassis. If it comes up, but looks like the same as it did with the working tube, then you'll know that both tubes are "good".

If it doesn't glow, then either find somebody with a rejuvinator and test it just to make sure or put it up on Ebay as "untested" :rolleyes: and save your parts money.

If the tube is good, then put money into the chassis to try and fix it (or send it out). I have done it the hard way (spent the money on rebuilding the chassis) only to find the tube had a hairline crack and the vacuum got let out.

ken
 
I went through all the recommendations last night, and believe I have found the problem.

First off, I was testing the wrong part - I was testing the regulator instead of the HOT. HOT tests fine. That'll teach me to not work with a manual. ;)

I inspected all solder joints and didn't see anything really out of the ordinary. Then I started looking at every component for damage. Cap C20 next to the HV shutdown pot was black and bulging out the side. Houston, I think we found the problem!

I'm gonna see if I can pick that specific cap up at rat shack to see if the monitor will work with it replaced. I'd rather see what I'm up against than blindly start replacing parts - that is expensive! All of the major parts have obviously been changed before by looking at the solder joints. The flyback has white knobs, but there isn't a single stress crack on them.
 
Best thing rat shack had was a 10uF 35V capacitor. IIRC, the voltage has to be exact. Would this be correct on capacitors?

The 10uf has to be exact. The voltage rating can be equal to or greater than the original value, just not less than....
 
if its that ez that would be sweet!
hey if thats the one right at the shutwown out, replace the twin right nex tto it as well
 
Well I replaced the cap, and guess what? It wasn't that easy. :rolleyes:

This time I could have swore I at least heard it degauss. No neck glow at all though. Next time I'll have to put it in another cab for testing, because the Outrun cab does not allow access to the tube or chassis.
 
My current plan of attack is to test the tube this weekend, then put in an order to Bob Roberts for everything I need.

That'll be the only cap I buy from Rat shack - $1.25 a pop is a little too much.
 
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