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Originally Posted by earlyfilm
I agree with Old Coot88, if the TV had been working normally after the rebuild before this problem developed, then it most probably is the Horizontal Output tube.
There is a lesser chance that it is the Horiz Osc / Horiz AFC tube.
Another test would be to observe in dim light and see if the Horizontal Output tube's plates are slightly glowing when the tube warms up. If so, it is either a failing tube, or something in the circuit is throwing the voltages off.
In these early sets a misadjusted horizontal setup or failing component can cause the horizontal output tube to pull too much current.
In this case, if replacing the tube does not cure glowing plates, I'd go after the problem with a VOM rather than the 'scope that you mentioned.
If the problem started with the rebuild, in addition to the above, also include the C8 (Sams) cap or C91 (Factory) cap in series with the horizontal side of the yoke. C8 in Sams is shown as either a .5MFD 100V paper(?) or a .5 ohm at 15,750 electrolytic, while C91 in factory is only listed as a .5 ohm @ 15,750 cycles 100 volt electrolytic. This Cap can change the loading on the flyback and possibly cause ringing.
That big boy should be an electrolytic. A paper cap might work OK, but a ceramic probably will not.
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The set did nothing aside from heat the ambient air with its electrolytics when brought up on the variac, so I have no idea if this problem existed prior or was something I built in. The plates of the HO tube look perfectly normal; no blue glow or abnormal heating.
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And speaking of "cap" or "trap", who is the character that replaced Admiral Ackbar in your avatar?
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That is "Pilot" from Farscape on the CTC-7. I miss Ackbar but it was time to change thing up a bit.
Quote:
Originally Posted by Down Under
Assuming that it's not a tube, why not try a can of freeze it spray, alternating with a hair dryer? I've found lots of faults that way over the years. Assuming yours is a heat related fault, of course.
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YES. I'm going to try this. A great suggestion.
Quote:
Originally Posted by Penthode
In standard flyback circuit operation, the left hand deflection is through the damper tube. The right hand scan is through the horizontal output tube. There appears to be a high frequency oscillation occurring when the horizontal output tube conducts.
What does the waveform on the control grid of the horizontal output tube look like?
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Ah okay, I did think that it was the opposite of this. If this is the case, there are plenty of more components to suspect.
First I'm going to try the old freeze spray trick, then get some VOM readings and as a last resort haul in the scope.