Head-Scratching G07-CBO

Peale

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G07-CBO. Reading a B+ of ZERO. No heater.

Full cap replacement and flyback.

Was received with bad horizontal output transistor and voltage regulator. Replaced.

R903 was found to have one leg broken off at the board. Repaired - no change.

I've gone over the circuit eleventy times, I'm obviously missing something. If I read voltage at F901 I get ~140VDC. So it's coming in and being rectified, but then it ends somewhere.
 
The usual location - end of the big white resistor (which number escapes me @ the moment). Both ends read a big fat zero. And it meters as okay.
 
Well, I'm guessing you checked the value of that R903 to make sure it is still 4.7 ohms, right?

The next step is to check the voltages on B1/B2/B3 (connected to the voltage regulator). If you have 140v on FR901 (both sides) and R903 is good, you should have:

B1 - 120 vdc
B2 - 120.6 vdc
B3 - 145 vdc

Also, check X901...
 
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I was /sure/ that I'd tested R903, but I had not. Completely open. I got so excited having found it disconnected that I failed to follow thru and test it.

Took one off a donor chassis for now. Fired it up, and it immediately blew F901. Normally I'd blame either the VR or horizontal output transistor, but they're brand new (unless they blew while R903 was out of commission). Testing now..
 
Well, I'm guessing you checked the value of that R903 to make sure it is still 4.7 ohms, right?

The next step is to check the voltages on B1/B2/B3 (connected to the voltage regulator). If you have 140v on FR901 (both sides) and R903 is good, you should have:

B1 - 120 vdc
B2 - 120.6 vdc
B3 - 145 vdc

Also, check X901...

on miy monitor R903 give me over 6.5 ohms is it good or not
anr r 904 2.4 k???
 
on miy monitor R903 give me over 6.5 ohms is it good or not
anr r 904 2.4 k???

I'm going to suggest you check the schematic for your monitor. Should be on ArcArc.

The fuse blew on mine because the ceramic insulators for the voltage regulator were not present. It came to me like that. When I replaced it I blindly just swapped it out and didn't give the missing pieces any thought. I raped some from an old TV, swapped them in and fired it up. Fired right up.
 
I'm going to suggest you check the schematic for your monitor. Should be on ArcArc.

The fuse blew on mine because the ceramic insulators for the voltage regulator were not present. It came to me like that. When I replaced it I blindly just swapped it out and didn't give the missing pieces any thought. I raped some from an old TV, swapped them in and fired it up. Fired right up.

ok is it a free sample of schematic of the chassis??
 
g07fbo902.jpg
 
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