G07 blew the little fuse, why?

keithsarcade

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Well my RoadBlasters just went thru another monitor, this time a rebuilt G07. No power, but it is getting 118v at the connector. Found the little fuse (near the big gray cap) is blown, so hopefully a simple replacement will get this one going again. My questions are what fuse do I need, and what might have caused this one to blow? Could there be an issue with my PS, or is it just coincidence? I previously had a rebuilt K7900 in here and eventually the tube died, although the chassis never did. The G07 in it now was showing the same symptoms as the K7900 did (taking awhile to warm up to a sharp picture), and now no power since yesterday after it was left on for a few hours. Whaddya think?
 

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Usually when F901 blows it is usually a shorted HOT or bad flyback. Would start there. Test the HOT, then carefully check the fly for cracks.
 
How exactly would one "test" the hot?

I did see what looks like a hairline crack on the flyback, looks like someone tried to patch it.
 

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Meter should be on diode check and then check outside leg to middle leg and you should get a .5volt reading or so. since your flyback looks blown i would replace the horz. output even though it may check good.
 
How exactly would one "test" the hot?

I did see what looks like a hairline crack on the flyback, looks like someone tried to patch it.

Yep, the fly is toast. I'd say that is the issue. But you should probably replace the HOT while your at it.

To test if the HOT is shorted, test the continuity from the metal case of the HOT to the frame. If shorted, you will get continuity. If ok, you willl not get continuity.
 
Heres a better shot of the fly. I'm not so sure this is acually a crack. Looks more like a seam. What do you think?

Second photo is near the center of the chassis, looks like it got hot. Cant tell if its fresh or not, but the legs on the cement resistor look corroded, guess this also needs to be replaced?
 

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There are no seems. The fly is definitely toast. It even looks like it took a shite.

Cement resistor is probably ok. Start with the fly and a new HOT along with a fuse.
 
What you're seeing is a crack with the epoxy potting material oozing out after it overheated.

You see cracks and ooze somewhere in the case when they die.

If you want to have some fun, I'll tell you what to do.
Take an alligator clip jumper lead and jump over the blown fuse. Plug that sucker in and it will usually POUR smoke out of the flyback.

Have your camera ready though. We want to see.

Kerry




Heres a better shot of the fly. I'm not so sure this is acually a crack. Looks more like a seam. What do you think?

Second photo is near the center of the chassis, looks like it got hot. Cant tell if its fresh or not, but the legs on the cement resistor look corroded, guess this also needs to be replaced?
 
If you want to have some fun, I'll tell you what to do.
Take an alligator clip jumper lead and jump over the blown fuse. Plug that sucker in and it will usually POUR smoke out of the flyback.

Haha. Already pulled the chassis though, and too lazy to put it back in before the repair.

New flyback and hot it is then. Anyone got these laying around before I order from Mr. Bob Roberts?
 
Well my RoadBlasters just went thru another monitor, this time a rebuilt G07. No power, but it is getting 118v at the connector. Found the little fuse (near the big gray cap) is blown, so hopefully a simple replacement will get this one going again. My questions are what fuse do I need, and what might have caused this one to blow? Could there be an issue with my PS, or is it just coincidence? I previously had a rebuilt K7900 in here and eventually the tube died, although the chassis never did. The G07 in it now was showing the same symptoms as the K7900 did (taking awhile to warm up to a sharp picture), and now no power since yesterday after it was left on for a few hours. Whaddya think?

Did you replace the flyback when you rebuilt the chassis? It has been discussed here many times that if you rebuild the GO7 Chassis, you should replace the flyback if it is original. The additional stress of the new caps and or HOT (if you replaced that) will accelerate failure of the flyback.

-VJ
 
Don't forget to discharge the filter cap. If that little fuse is blown, it has no way to discharge itself and it can sting ya!
 
Naw... but I DID get a nice zap from a neckboard of a K4900 yesterday as I was trying to adjust some pots while it was in the Pac cab. Not sure what the voltage was, but it felt like 110v or thereabouts...
 
Naw... but I DID get a nice zap from a neckboard of a K4900 yesterday as I was trying to adjust some pots while it was in the Pac cab. Not sure what the voltage was, but it felt like 110v or thereabouts...

FrizzleFried, the human voltmeter! :D
 
I bought the monitor this way, so couldnt tell ya. The flyback dosent look that old though, is there a way to tell if its the original?
 
yes and just short an old screwdriver across the terminals

It was said that while that dischargees it, it will lessen the lifespan/performance of the CAP. Use a high watt resistor to drain it slower or use a light bulb as was demonstrated in the other thread.
 
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