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Hi All,
Got a chance to poke around a bit on the set. The vert/horz centering adjustments do indeed work, I was spinning the shaft of the magnet, not the magnet itself! Duh. I have the picture nicely centered now. The vertical linearity definetely doesn't work. Just to confirm, the vert. lin. is the inner of the top (brightness) pot. The pot only has one wire coming to it, to the center contact. The center contact has about .2 ohms resistance to chassis ground. One side of the pot adjusts fairly smoothly from 3 to 1200 ohms or so and then goes infinite in the last bit of the turn. The other side goes from about 1.8 ohms to to 300 or so, then jumps up into the kOhms and gets worse from there. Measuring the resistance at pin nine of V9 I get 296 ohms and it doesn't vary when the pot is turned. So a bad pot. What I don't understand is why it only has one wire connected to it. The schematic clearly shows one side goes to R58 and the wiper to ground. If I understood how it is connected I could sub in a 1k pot to test while I look for a pot. I didn't have the time to disconnect everything to the set so I could look underneath and follow the one wire that is connected to the pot.
Didn't dig into the hum issue but did notice that it does vary with the volume and is there with no signal applied. The electrolytics have been replaced, of course. Later I will ground the control grid of the 12CA5 and see if it persists. If I can get the vert. lin. and hum issues resolved I'm going to call this set done.
Thanks!
Jonathan
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