|
I've been chasing this thing in circles for weeks now. Time to call in the calvary! Maybe some of you, who unlike me know what you're doing, can point me in the right direction? Part of the Photofact schematic is posted. To recap:
I had 26kv & a nice raster. As I was adjusting the HV I suddenly watched it fall while the HO tube cathode current jumped & the picture started to fade. I shut it down.
Where I'm at currently: HV is around 12kv with a dim raster, pulled in on the left about 1/4 of the screen. It takes perhaps 45 seconds for the HV to come up. Cathode current is on the high side. The horizontal limiter coil is getting very hot, and in short order; I put a meter on both sides of it and each is seeing over 200ma. After running a few minutes the core of the flyback is hot. There are no outward signs of distress to the flyback (no dripping wax, no cracks, no arcing). All resistance readings on the fly are correct.
The set has been recapped including the doorknobs. I didn't change C164-167 but did a quick & dirty sub with the closest thing I had on hand & nothing changed. I tried a temporary swap to a later RCA 21" yoke with no change. All tubes in the circuit have been swapped more than once with NOS. Disconnecting the HV regulator had no effect. I tried adding R268 & C239 which Philco added to later runs-no change. External sources for horiz drive made no change. Chassis voltages, last I checked, were good.
Anything I'm missing? I know the problem is right in front of me; I just can't see it.
__________________
Bryan
|