Thanks for the ideas. Here's what I found.
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Bridge the 100 mfd cathode bypass.
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Tried, no change.
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Rotate v lin while measuring cathode, pin 9. It should go to 0 at extreme end.
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If you mean going to zero volts, it never goes below about 20 volts. Resistance of the v lin pot varies from about 10 to 770 ohms. I wonder if this is a replacement? The manual calls for a 1500-ohm pot with a stop at 180 ohms. This looks like a (roughly) 750-ohm pot and someone added a 950-ohm/1W resistor in series to make a max of about 1700 ohms. So, with the resistor the pot is varying between about 960-1700 ohms. Shorting that resistor didn't change the height noticeably.
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Bridge electrolytic on the 275 volt source.
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Tried, no change. The 275V source measures 273V.
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Recheck cap values that were replaced. C 40 will have most effect on height.
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Rechecked, all caps look OK. I replaced C43 (.0015/1KV) by wiring two .0033/630V in series. In Sams, C44 is listed as .033, with .022 as an alternate value. I temporarily subbed a .022; no change.
I noticed one difference: R55 (between pin 8 and vert hold pot) should be 33K and I installed 39K for some reason. (Perhaps 39K is what I found there.) Not sure how important that is. I measure 8.6V on that pin; Sams calls for 7.5V and the Philco manual calls for 10V.
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Make sure pin 7 measures 68 k to ground.
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It measures 67.5 K.
Regards,
Phil Nelson