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#1
08-01-2006, 03:30 PM
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philco printed RC vertical network
Hi: Trying to restore vertical drive in a 1956 philco top line 21" console; away from set now and can't recall chassis #. But all fingers point to a ceramic encased module I am planning on fabricating on perfboard with discrete parts. Anybody have experience with these being the culprit in shutting down everything downstream of sync separator? Starting from totally dead, I replaced nearly every cap in it and was getting a wobbly, hum-laden picture. Then something collapsed under load and we are back at square two. Sound is present. Horizontal oscillator squeal is heard but no HV. 580 boost from flyback sub winding is running 30V. Does the VOT make that 580V or does it come from the HOT and go into the VOT? Having trouble making sense of the schematic. THank you. --Tom in AZ
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#2
08-01-2006, 10:10 PM
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I could be wrong, but I think usually the boost comes FROM the horizontal.
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#3
08-01-2006, 11:46 PM
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I can be more help with a chassis number. 330, 390, 440 etc for 1956.
I would suggest bridging filter caps first. If that doesn't prove helpful then go through these steps. Assuming you've tried obvious tubes, damper, horiz output, damper, 1B3. 1. Remove damper tube and 1B3 cap and make sure damper cathode and horizontal output plate go to 0 volts DC, or so. If so, put everything back. If not, look for shorted caps from boost to B+. 2. Short across the horiz osc coil, ground the sync input grid on the horiz oscillator and see if the oscillator runs on freq. Adjust the horiz frequency control for proper freq. Remove jumper across coil and tune coil for proper freq. If nothing works, get a chassis number and I can be more specific. Last edited by Don Lindsly; 08-01-2006 at 11:48 PM.
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#4
08-05-2006, 07:26 PM
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chassis is a tv392. using a sams 321 folder 11. With the yoke unplugged, the B+ on the vertical oscillator is almost normal. WIth yoke connected, voltage drops to a third of required. instead of -2V on grid of noise inverter, I have -27V but cannot determine how or why that could be. passive resistance values are all near normal.
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#5
08-06-2006, 12:16 PM
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RF, IF and audio are all OK. all tubes including CRT test good on dynamic tester. electrolytics all new; main power supply busses have plenty of juice. This is open plea for help either on here or off the forum to me direct. [email protected] Thank you. --Tom
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#6
08-06-2006, 06:02 PM
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Remove the 6S4 vertical output tube. If the high voltage returns, the vertical is loading the boost circuit. Look for shorted tubes, coupling caps, etc. If not, then;
with the yoke connected, measure the boost voltage at the damper cathode. Unplug the yoke and measure again. If it increases when the yoke is unplugged, it points to a defective yoke. Don Last edited by Don Lindsly; 08-06-2006 at 06:09 PM.
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