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41-300 transformer values
#1

Hello,
I'm new to repairing/rehabbing vintage radios, so please be kind Icon_biggrin . I have the package of information from Chuck, which is excellent, however nowhere on the schematics are there any values for the transformers. Is there anybody or anywhere I can obtain these? I have tried all the different sites, but they have the same schematic.

Thank you in advance for your help.
Glenn

Happily back in Illinois..not.
#2

Hi Glenn and welcome!
Well what you will have to do is some reverse engineering. Pull out your handy tube manual and add up all the filament current of your 6V tubes and pilot lamps. I came on with 4.1amps (@6.3V) The 80 tube takes 5v 2amps. As for the HV current wise the 80's max output is 120ma. Generally I figure about 10ma per tube except for the output stage. Push-pull 42's could haul down as much as 80ma. With that calculation it come to about 160ma but that is is more that the 80 tube can put out. Granted at 245v the 42's aren't running at full tilt (about 75% of full tilt). HV Needs to make 245vdc+about 15v bias. Total is 260vdc. There will be a 50v loss per plate across the 80 when the ac is rectified and turn into dc. The 80 tube is a full wave rectifier Which means that it will only will rectifying one half or the hv winding at a time so you will need the hv winding that is twice voltage. So bottom line what you are looking for is a transformer that can provide 6.3v @ 5A, 5v2A, and 310vac-0-310vac or 620vac end to end @120MA. The hv winding isn't super critical if you find something that is within 30v or so it should be fine.
Good luck with your project! From the diagram is looks to be a nice set with lots of audio.
Terry

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
#3

So after really reading your post I guess I would ask which transformer are you concerned about ? I assumed you where talking about the power transformer that is what I addressed in my previous post.
Terry

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
#4

Thanks Terry, Your post was very informative. I'm still learning and any help I can get is appreciated. I should have been more specific in my original post, but looking over the schematic I realized that those values were missing as well. I guess what I'm looking for is the resistance values for the speaker and the output transformer. If they are hidden on the schematic please let me know. I would like to know if I need to look for these parts before I complete the Wiring/Cap/Resistor replacement.
Thanks again for your time and help.
Glenn

Happily back in Illinois..not.
#5

I think most would replace all of the wax/paper caps and the electrolytics. The resistors typically tend to be within spec. I would measure them before replacement. Spec would be +/- 20% of value noted by the color code on the resistor. Check value with the one on the diagram as sometimes it may have had a repair that a different value was used. When measuring the resistance of a resistor that is in circuit make sure that it doesn't have a cap in parallel with it. If you do it won't be the correct value of that resistor. Since you are go to be replacing the paper caps it's a good time to measure the resistors.

Wouldn't worry too much about the transformers rf, if, power, and output. They typically don't change value. Can be checked for dc resistance (continuity) with an ohm meter. Most of them can be found as new replacement parts except for the rf coils/transformers. Sometimes you can repair a bad one (open winding) if your lucky.
Terry

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
#6

I did check them and got a value so none are open. We'll see how it performs once it's all back together. The rubber wiring is a chore. All of the yellow leads are crumbling. I repair equipment all day, but find the change relaxing. Icon_rolleyes

Happily back in Illinois..not.




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