Posts: 8
Threads: 1
Joined: May 2017
City: Germanton, NC
Once again your expertise is invaluable.
The power transformer secondary resistance reads a little low. The schematic has half the secondary at 420 ohms and the other half at 400 ohms. I get about 300 ohms on one side and about 345 ohms on the other. The primary reads 18 ohms just as the schematic says it should and the filament windings read <.1 ohm. Should it be replaced or is it within tolerance?
Einstein once said, "I have no special talents, I am only passionately curious."
Jim
Posts: 7,285
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Wouldn't lose any sleep over it. Would measure the ac voltage @ the rectifier plates (without the rectifier in place) to see if it's close. Then leave it on for a little while to see if the transformer get hot.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 8
Threads: 1
Joined: May 2017
City: Germanton, NC
I have searched for a 270 ohm resistor the schematic calls shows, however, no matter how many times I trace the old wiring I come back to a 470 ohm resistor that looks as if it was put in after manufacture. The soldering on the leads is shiny and sloppy. The after market notes I have do not indicate a change however my notes are probably incomplete. Should I replace the 470 with a 470 or replace it with a 270 the schematic indicates?
Thanks...Jim
Posts: 7,285
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
For now I'd leave it. What it does is set the - bias voltage for the 41 and 7C6. THe important part is when you get it working measure the - voltage on pin 4 of the 41. RCA sez you need about -15vdc there. If you lower the resistance you will low the amount of bias voltage. If you do change it you'll need a 3-5watt job to replace it.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 07-26-2017, 07:28 PM by
Radioroslyn.)