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Philco 40-165 Motorboating?
10/17/2007 1:05:09 PMAndy
Hi,
Been a long time since i was here last! I am getting a very strong motorboating with no response to volume control,or station selector,but a strong response to the tone control. Motorboating becomes more rapid if i touch top of 1232/7Z7 tube. Tubes are new replacements.I have replaces all caps,and out of spec resistors. I am looking for a mis-wiring,but it looks right.I'm still working on it. Your input would be helpfull! I'm glad to see Norm is still here!!!
10/17/2007 2:01:34 PMNorm Leal
Hi Andy

Good to see you are back. Motorboating is a low frequency oscillation. Having no response to the volume control shows the problem is in audio & power supply sections. When replacing caps were electrolytic filters replaced? Three sections in cap #53.

http://www.nostalgiaair.org/PagesByModel/334/M0013334.pdf

Notice two sections have negative connected to center tap of the power transformer high voltage winding. The other section negative is grounded to chassis.

Norm

:Hi,
: Been a long time since i was here last! I am getting a very strong motorboating with no response to volume control,or station selector,but a strong response to the tone control. Motorboating becomes more rapid if i touch top of 1232/7Z7 tube. Tubes are new replacements.I have replaces all caps,and out of spec resistors. I am looking for a mis-wiring,but it looks right.I'm still working on it. Your input would be helpfull! I'm glad to see Norm is still here!!!



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