Home › Forums › Electronics Restoration › Thorcraft B71 resistor

Viewing 3 posts - 1 through 3 (of 3 total)
  • Author
    Posts
  • September 13, 2017 at 8:24 pm #9526
    Rod
    Forum Participant

    Hello forum

    Unfortunately, I bought this radio without doing much research on it. Good thing it was cheap. A standard 2 prong AC cord was on it so I thought it was a 115v AC unit. Well….so did the previous owner as it was plugged into wall outlet at some point. Turns out it’s a 32vdc unit. Thorcraft did not publish schematics apparently so it’s a guess as to value of the burnt power resistor in the photo linked below. Or perhaps someone owns this radio and can assist. One end of the resistor is fed the +32vdc from the switch and the other heads to an electrolytic cap lug of 20mfd. That in turn has leads that go to pin 4 of both 25L6’s and a 6SA7. It also leads to pin 6 of both 6SK7’s Any info on what value would be much appreciated. Thanks!

    Resistor image here

    Attachments:

    1. IMG_4124.jpg

    September 20, 2017 at 3:21 pm #9556
    phil
    Forum Participant

    not sure about the value. can you read any of the markings? is it open? I believe that was a local manufacturer to BC, so that might make it a bit special . I once had a table set and gave it to a fellow member who was in touch with one of the daughters or granddaughters who want it for a keepsake. most of the others I have seen locally were pretty plain looking consoles

    maybe someone else could guide you through trying to look at tube voltages ( you could compare to the RCA manual for the nearby tube pinouts) Perhaps that could give you some idea of the voltages expected for the tubes it has. Maybe you could use subsitution of other resistors until you arrived at something that gave you a realistic voltage drop. Unfortunately Im not technically savvy enough to help with this as much as I;d like to be able to, but others with more electronics might be able to help more.

    Phil

    September 20, 2017 at 6:43 pm #9566
    Rod
    Forum Participant

    Thanks for the reply. After much research/trial and error, I was able to get the set singing again with a 27 ohm resistor. I had to replace a number of other out of spec resistors, tubes and all the caps of course. Alignment was waaay off as well. Not a real power house of a radio but at least it’s up and running. There is nothing available, that I could dig up, for service data on this unit unfortunately.

    Rod

  • Author
    Posts
Viewing 3 posts - 1 through 3 (of 3 total)
  • You must be logged in to reply to this topic.