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Old 11-21-2010, 09:26 AM
DaveWM DaveWM is offline
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Join Date: Feb 2009
Location: Orlando FL
Posts: 5,607
decided to check the cat current at reduced line voltages.

I put the set on a variac and dropped it to 105vac, cathode current on the HOT went to 180ma from 220ma with no change in HV (shunt prob just not working as hard) and no change in vert/horz size (compensation parts like VDR's and other bias componets prob accounting for that).

bottom line is I think this set was engineered to work at lower line voltages, with higher voltages just generating more heat. I suppose this is a trade off on designs that did not include power supply voltage regulation.

You can bet I will be using a variac to run this set. I kicked around an idea adding some resistance to the screen resistor on the HOT, set it up to operate at 120v and still get the lower HOT current. Not sure if I want to go adding circuitry. It would be nice if I could engineer in a jumper that would switch in a voltage drop, I will have to look over the chassis for this. I would prefer to make min changes in the orig design. A bucking transformer would be good but these old sets pull a lot of power, not sure how to size that.
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