G07 Issues

Peale

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I have two G07 monitors, here's what I did:

Monitor 1 was totally dead. F901 blown. Replaced flyback, Horizontal Output Transistor, F901 and recapped. Came up with a perfect picture. Let it bench for a while.

Monitor 2: did not fire it up as the tube was damaged. Replaced tube with one from a donor TV. Figured to use the newly rebuilt G07 to converge the tube. It was working well, and the convergence was even pretty good - but then I thought I'd get crafty and try and converge it some more. Stupid mistake! I made it even worse. Suddenly the whole thing shut off. On investigating, F901 is blown again! The Horizontal Output Transistor appears to be okay (black lead to frame, red to case) and I'm getting very high resistance (like 10K or something, it's in the shop and I can't check it from here).

So why did it blow?
 
Did you use a G07 yoke on the new tube? Did you bolt the chassis into place for the tuning, or did you just set it in there without the bolts as you were just doing a "quick check"? Everything powered via the isolation transformer? use the new tubes degauss wiring or the old tube's degauss wiring?
 
1) G07 yoke used - check.

2) Chassis not bolted into place, but it didn't go anywhere either.

3) Always with an iso on any monitor I test, even if it doesn't need it.

4) degauss not plugged in at all, and the G07 one was moved to the new tube. It goes behind the shield.
 
While I'm at it, at one point I had my convergence close to perfect, but the bottom was a wee bit squished. How can I adjust that out?

And is it my imagination, or is there no brightness/contrast on one of these? This is my first G07.
 
If you've got the yoke perfectly even (and not slightly tilted causing the squish), you may get a result by changing a cap size. I believe C517 and C518 are normally a 100uF and a 220uF, right? If you change them both to 220uF, it helps square the picture more, although usually you see the "squishing" along a horizontal side and not a vertical side.


And the only brightness control is on the front right (bottom pot) attached to the flyback. Otherwise just adjust the 5 color pots on the neckboard...
 
I used a fuse holder attached to pair of alligator clips to see what would happen once I replaced the fuse. All I had on hand was a 3/8A fuse, so I went with it. It fired right up. I don't know what happened, but I'm glad the horizontal output transistor didn't blow.
 
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