philco model 77 - Printable Version

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+--- Thread: philco model 77 (/showthread.php?tid=969)

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philco model 77 - philco phan - 02-13-2008

hi fellers,i'm having a brain fade tonight,where do i measure b+ in this chassis? and can the last interstage trans be r/c bypassed? pri and sec. are both open,thanks.

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- planigan - 02-14-2008

philco phan, I believe between the center tap HV secondary and point J on the schematic will give you full B+ available. Center tap to plates for B+ at tubes. B supply not grounded to chassis in this set. PL

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- Ron Ramirez - 02-14-2008

The main B+ would be measured between point D and one of the following points: the center tap of the high voltage winding of the power transformer; pin 2 of resistor (26); or pin 2 of the multi-section filter condenser can. Point J carries a lower B+ voltage that has been dropped by the speaker field coil.

If both primary and secondary of interstage transformer (22) are open, then no, one cannot generally convert it to R/C coupling since the secondary is feeding two tubes connected in push-pull. You'll have to replace this transformer with another one.

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- philco phan - 02-15-2008

thanks guys,b+ is good,i'll just r/c bypass to one of the 45's to confirm radio is operational until i can find a suitable tranny,phil

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