46-1201 model 128 restore and question - Printable Version
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+- The PHILCO Phorum (https://philcoradio.com/phorum)
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+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: 46-1201 model 128 restore and question (/showthread.php?tid=7862)
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RE: 46-1201 model 128 restore and question - Mondial - 11-17-2013
If resistor 27 is completely open, that will certainly cause a problem, but then you would have no voltage at all on the plate (pin 2). You can try replacing it and see what happens.
I would also try to trace out the wiring to pin 7 and see why there is voltage present there. Pins 4 and 7 should be connected together inside the 7C6 tube, so there should be no voltage between them.
RE: 46-1201 model 128 restore and question - tig1 - 11-17-2013
Sooooo, apparently i've made a faux pas. The last 3 tubes i mixed up. Sorry about that. The readings seem much better now. Here's the new readings.
RE: 46-1201 model 128 restore and question - Mondial - 11-17-2013
That's much better. Now it looks like resistor 27 is really the problem. You only have a half a volt on the plate pin 2 where there should be 55 V.
An open resistor 27 would be the cause since it should supply plate voltage to pin 2.
RE: 46-1201 model 128 restore and question - jerryhawthorne - 11-17-2013
+1 for Mondail, smarter than me. The new measurements really focus on that tube and #27 resistor. Now the voltage is going low, prior readings were going high.
Jerry
RE: 46-1201 model 128 restore and question - tig1 - 11-23-2013
Yup, replaced #27 resistor and lots of volume! had to remove the cone to get all the grit and metal particles out of the center but sounds great now except for some buzzing and humming depending on the station tuned in. Could this just be an alignment issue? I still have some resistors i want to replace because they're over 10% off.