Power transformer help

[Original Burnedfingers]

Expert help needed for mono block project.

I have several power transformers out of some Wurlitzer organ amplifiers. They have reluctantly given their lives for my next project. The transformer originally drove a 5R4.6SN7,(2)6L6CG's.
I am wondering if the heater windings are sufficient to run(2) EL34's, a 6Sl7 and 6SN7. There isn't any marking/manufacturer on the transformer just two numbers...10732 and 413348 located in different places on the transformer.

Is there a way to find out how many mA the transformer puts out?

Size is larger than a Dynaco Stereo 70 transformer. Unloaded tube rectified output is 500V unloaded.


Thanks
Joe

[rcavictim]

Originally posted by burnedfingers
Expert help needed for mono block project.

I have several power transformers out of some Wurlitzer organ amplifiers. They have reluctantly given their lives for my next project. The transformer originally drove a 5R4.6SN7,(2)6L6CG's.
I am wondering if the heater windings are sufficient to run(2) EL34's, a 6Sl7 and 6SN7. There isn't any marking/manufacturer on the transformer just two numbers...10732 and 413348 located in different places on the transformer.

Is there a way to find out how many mA the transformer puts out?

Size is larger than a Dynaco Stereo 70 transformer. Unloaded tube rectified output is 500V unloaded.


Thanks
Joe

Your plate loading will be similar so that is not a concern I think. You are not going to use the 5 volt filament winding previously used for the 5R4, so that gives you a few VA surplus in the transformer core and primary. The only real concern is the extra 3 amps or so you are going to ask of the 6.3 volt fiament winding. Because this transformer was made for a semi commercial type application in a time when transformers were made more conservatively as a generality and can stand more overload abuse, I would say you might be fine, especially for a home amplifier that won't be used for more than a few hours at a time. Best to connect all the 6.3 volt tube filaments to the transformer's 6.3 volt filament leads as would be in your design and apply mains voltage to the power transformer in question. If the measured voltage on the 6.3 winding is less than 6.0 volts and rises significantly when one 6CA7 is pulled from the circuit your transformer filament winding might be of too light guage to handle the extra filament current load. If you see 6.2 or 6.3 volts under full load you should be just fine.

These voltages will also depend on if the transformer primary was wound for 115 vols or 120-125 volts when made and what line voltage you have in your home. The numbers I tossed at you are not hard values. Let the force be your guide Luke!

[Original Burnedfingers]

From the remaining (2) working units out of (4) I threw in a set of tubes and measured voltages. My 6.3 voltage actually measures 6.77 with the 6L6GC's in circuit. I pulled them and installed the EL34's and the voltage dropped to 6.60V so I assume it will be ok.
I ran it into a dummy load at about 50% power for about 1/2 hr and then normal use after that with no transformer heat up.

The tag on the amp says 120V input instead of 115V. The construction looks like 40's to early 50's with silver wire and oil paper caps.