The PHILCO Phorum

Hello Philco collector friends !!
I am new here at the Philco Phorum, and I have a peculiar probelm with a Philco 39 - 55 radio set! The radio did not play originally and needed a lot of new parts like capacitors and resistors that that were either leaky or migrated way out of 20 percent tolarance (resistors). The set did not have an original output transformer when I acquired the set, I temporarily installed a transformer that matched the impedance values of the 42 output tubes to get the set going,
I was succesfull at this part, now here comes the problem, I have just installed an original type output transformer with the feedback tap (I think) connected to the bottom of the volume control.
The set plays BUT when i turn the tone control to max treble I get a high pitch feedback, then as I go toward BASS the feedback disappears and set sounds normal, then when the control is at max BASS a low frequency feed back occurs!!
My question is does someone have the color code of the transformer wires on both primary and secondary sides? What wire exactly, is the negative feedback wire on the secondary? I assume it is the wire that has a green tracer on it? and what two wires go to the speaker? is it the white colored one and the solid green one? If i ground out the bottom connection of the volume control the set works O.K. but at a little louder setting of the volume control ! the remote control section was reworked also and seems to work O.K. including the stepper relays and contact wiper assemblies after a little cleaning and light relubing. I think my problem is somewhere in the wiring of the original type output transformer somewhere along the line !! Thanks for any help in advance -------------- John A Bellas

Hi John and Welcome!
I like to take the simple approach. Would use an ohm meter to find the ct on the secondary. Double check that it's going back to the volume control. Be sure that you have a good ground connection at the speaker. The two ends of the secondary aren't critical, if they are reversed it can cause the oscillation problem you are having.
Good luck w/it
Terry

Hi John

There is no color code for the original output transformer in the schematic. You'll just have to experiment with the output wires; as you are getting regenerative feedback now, try reversing the outer leads of the output transformer secondary. But first, as Terry said, use an ohmmeter to find the center tap of the secondary. That is the lead that feeds back to the bottom of the volume control, and the wiper arm of the tone control.

Hello Fella's--
Thanks for the reply on the problem with the 39- 55. I tried reversing the outer leads on the output transformer and while this helped reduce the fedback problem i wound up with slightly distorted low/bass sounds and slight distortion when the
control is advanced to max treble, I am wondering now if have the correct type output transformer? ---- For now I am leaving the feedback loop to the volume control disconnected, I am currently checking out the remote control box to see if
it might need any new components, I checked out the receiver remote control section by setting up my frequency generator to get a pulsed output, and when i strike the right frequency setting I can activate the relays and select volume up/down
and preset radio stations. I will get back to the feedback problem in about a week, I will post my findings then, Until then --- I Wish everyone Happy Holidays, and or Merry Christmas and Happy new Years !!!! ----- John A Bellas