How to be a dumbass in one easy step...

modessitt

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Today I was fighting a G07 chassis in a converted Gorf cocktail, when I suddenly had a stroke of "remembering" and fixed.

So - I make the last repair, and stick it in to make sure it's working now. I have a mirror on the floor so I can see the screen as the top of the cocktail is open. I hook everything up, power up, and have a perfect pic!

Well, I'd been fighting it for a good while and was very excited that what I tried (based on something I detailed here a little while back and i'm fixing to bump again) worked, and I lifted the cocktail top upright to show someone. This is when I find out that in my haste to test it, I forgot to put the retaining screws back in, and the powered chassis slid out of it's placeholders and shorted against the frame with a loud POP!

:mad:

Of course, after replacing the blown fuse and suspect HOT, I can't get it to power up. B+ is at 160vdc. I've been over the chassis and can't find any bad parts. I grabbed another working chassis and used it to compare readings on all the various transistors, VR, HOT, IC, etc, and am getting identical readings.

So, what am I missing? I need this to work tomorrow...
 
What part shorted? Maybe there is a bad trace....

Did you try the good chasis in there?

-Mike
 
The good chassis is fine in there.

And if I knew what got shorted, I'd already have it fixed. I was just hoping for ideas right now, as I'm not finding it. There is a burn mark on the frame where it appears the filter cap shorted to the frame....
 
Both the big and little fuse good ? (well, the big one obviously should be in your case)
What about the fusable resistor FR901 ?
Measure the voltage going into and out of the voltage regulator ?
 
Both the big and little fuse good ? (well, the big one obviously should be in your case)
What about the fusable resistor FR901 ?
Measure the voltage going into and out of the voltage regulator ?

Both fuses and FR901 are good.

I'm going to change the VR next. Even though it measures out the exact same way as the one on the working chassis, I have about 160 on both sides of the big resistor...
 
How much high voltage is being generated? What does the high voltage probe read?

Anything? Too low? Too high?
 
Okay, as an update...

Monitor is in HV shutdown. I pulled X701 and did NOT get the monitor to come up. That led me in the direction that eventually had me replace IC501. Once I did that, the monitor will work with X701 pulled.

BUT - it will not work with X701 installed. Still in HV shutdown.

I have since replaced every single part that starts with a 9 with parts from a known working chassis, and it won't work. I have replaced rectifier diodes, VR, filter cap, disc caps, resistors, fuses, pots, jumpers - nothing.

When measuring the three legs of the VR (B1, B2, B3), this is what I have:

B1 - 163vdc (this is supposed to be my B+)
B2 - 155vdc
B3 - 172vdc

I also replaced C511, T501, X501, X701, the HOT, and a few other parts, trying to make a difference, and I'm not finding it.

I have done continuity checks around the flyback, and in the power section, but am finding no problems.

All this because the bottom of the chassis grounded out because I forgot I didn't have the chassis bolted in place. :rolleyes:

What the hell is wrong with this thing? The flyback is the newer style, and doesn't appear to be the problem, as the voltage isn't even getting there...
 
Uh, shyah?

It measured fine and I replaced it anyway. (I did say I replaced every 900 part, right?)
 
I'm actually testing in without even the tube connected. I've tried it installed, and now have it on my desk with only power connected while I measure voltages at various points. When you power up, you can hear the buzz at the cub for just a second before it cuts out. If I pull X701, it'll buzz continuously, but the B+ doesn't go down. I'm going to try another VR, as I had replaced it before replacing IC501, and I want to be sure...
 
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