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Originally Posted by Unimatic1140
OK guys I suspect the brightness control is the culprit. So I disconnected R35 and it read nearly a perfect 100K ohms. Then I measured from the input to the brightness control to the output of the wiper and it ranges from 25 ohms to 108K ohms from stop to stop. BUT when I measure from the input of the control to the chassis ground it shows only 135 ohms. Am I correct in assuming 135 ohms to ground is a problem?.
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Yes indeed. At the impedances involved, that would functionally be a dead short.
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If so is it safe for me to experiment by hooking up different resister ranging from 100 ohms to 50k between the output of R35 and the input of Pin 2 just to be sure this really is the problem, bypassing the brightness control?.
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What i would do first is this- disconnect the CRT grid (pin2) wire from the brt.control, and connect a 47K resistor to ground (in place of the brt.control element). Then connect R35 and the CRT grid wire to the junction. Then fire the set up. You probably won't get a raster at first. So replace the 47K with a 56K. If still no raster, keep bumping up the value till you get a raster. Optimize the ion trap adjustment and select the final resistor value for the brightness level you want. This'll serve temporarily till you figger out what's shorting out the control.
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Also the brightness control is a part of a combination, brightness/contrast control is this going to be next to impossible to find?
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Very probably it's fixable. But you may have to physically remove the control and disassemble it to find the short.