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Old 05-19-2011, 12:26 PM
old_coot88 old_coot88 is online now
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Join Date: Sep 2009
Posts: 2,646
To the OP:

At this point, and if you still have access to the variac, you might consider trying this:

Disconnect both primary leads of the vert.out transformer and drive it directly with the variac. Granted it's a sine wave instead of sawtooth, but will tell you a lot. You should get very robust deflection, probably at around half to full line voltage. This will tell you the tranny and yoke coils are good, thereby proving the fault lies somewhere "upstream" of the tranny.

If the problem remains, it's gotta be either in the tranny or the yoke (like a shorted turn that won't show up on a resistance check). Now disconnect the yoke winding and drive it directly with the variac (starting from a low setting). If deflection comes up, the yoke is good and by process of elimination, the fault would be in the tranny.

Of course if the fault is "upstream" all bets are off. The first place i would look is the plate load resistor of the vert.oscillator, if you haven't already checked it. I can't see it since i don't have the schematic of your set, so this may not be applicable. But in many sets that resistor is a very common failure and worth bookmarking*. Its value goes 'waaay high due to being hammered by a high level pulse. Bill(oc)

*Germaine to all makes and ages of '50s-'60s tube sets.

Last edited by old_coot88; 06-09-2011 at 11:36 AM.
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