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Doug, I have both the Sams and Tekfax (copy of the original GE factory schematic) at hand.
One note - there is a 50uF electrolytic (C179) in the 8AL9 circuit that causes poor contrast if it fails.
The only other tip is to replace C278 - they have a tendency to short, causing the focus circuit to arc. Its a 3900 pf HV Ceramic disc.
Also, the three drive controls are in parallel (9K ohms each, for a B+ load of 3K ohms) - if any of them were to open up, you'll get too much drive voltage to the cathodes. Real common problem, apparently - there is a Symcure in a 1974 Electronic Technician Dealer for the problem, as reported by GE. Replacement of the multi-pot assembly fixes it.
Key voltages:
GE defines on and off signal as antenna connected or disconnected.
8AL9:
Pin 2: 200V (on signal) 180V (off signal)
Pin 11: 3.8V(on signal)-5.4V(off signal)
Pin 4: 5.7V (on signal) - 6.6V (off signal) - this is tied to the brightness and brightness limiter controls.
Pin 10: 140V
6AC10:
Pins 2/5/10 - 165V
CRT:
G1: 90V (pins 3/7/12)
Screen controls are fed by boost voltages on one side and 280V source through R557 ( a 270K resistor) on the other side
Hope this helps,
__________________
Brian
USN RET 22YRS (Avionics/Cal)
CET-Consumer Repair and Avionics ('88)
"Capacitor Cosmetologist since '79"
When fuses go to work, they quit!
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