I need a PP audio input transformer for a Philco 16 cathedral. The part # is 32-7057. Schematic says pri is 420 ohm, secondary 260 ohm, I believe that must be either side of CT.

What is involved in replacing it with an R/C circuit?

Thanks.

Bob B.,

There are places that new type driver 1:3 transformers may be had. I believe Antique Electronics at www.tubesandmore.com is one place. Also you may want to check out the following url for some more posibilities:

http://www.antiquewireless.org/otb/resto802.htm

Clifton

:I need a PP audio input transformer for a Philco 16 cathedral. The part # is 32-7057. Schematic says pri is 420 ohm, secondary 260 ohm, I believe that must be either side of CT.
:
:What is involved in replacing it with an R/C circuit?
:
:Thanks.
:

Bob

Might be able to use R/C coupling depending on what what part of the transformer is open. Since the circuit is push-pull you need inversion from a transformer.

http://www.nostalgiaair.org/PagesByModel/139/M0013139.pdf

Here are some available transformers:

http://www.oldradioparts.com/2a23cfl.txt

You can also buy from AES, www.tubesandmore.com or Radio Daze, www.radiodaze.com . They both sell new audio interstage transformers. Most are step up 1:3 ratio. You can use it backwards as long as the winding has a center tap.

Norm

:I need a PP audio input transformer for a Philco 16 cathedral. The part # is 32-7057. Schematic says pri is 420 ohm, secondary 260 ohm, I believe that must be either side of CT.
:
:What is involved in replacing it with an R/C circuit?
:
:Thanks.
:

Hi Norm: I zapped the hi ohm secondary side with a charged 10 mfd cap. No change. With a 50 mfd cap. No change. With full B+. Presto! 420 ohms came down to 210. Balance is undoubtedly off but my 79 year old ears can't detect it. 77 year old radio sounds great and every part is original except one of two can electrolytics and some tubes.

Thanks again.

Hi Bob

Great, much better than using a modern part which will have different frequency response anyway.

Norm

:Hi Norm: I zapped the hi ohm secondary side with a charged 10 mfd cap. No change. With a 50 mfd cap. No change. With full B+. Presto! 420 ohms came down to 210. Balance is undoubtedly off but my 79 year old ears can't detect it. 77 year old radio sounds great and every part is original except one of two can electrolytics and some tubes.
:
:Thanks again.
:

Thanks for replies. The primary is ok. The sec s/b 260 ohms. It is 110 on one side and 420 on the other.

Hi Bob

The 420 section may have an oxidezed connection? Try this before giving up on the transformer.

Dump high voltage is the high resistance winding. Might try charging a 10 or 20 mf cap to 150 volts and connect leads to the high resistance winding. In some cases this will cause a bad joint to spot weld.

You could use R/C coupling from the driving tube to grid of the high resistance side winding. Transformer good winding has to be wired to give signal inversion. Center tap and good secondary winding can be reversed if necessary. If not right there will be reduction in output.

Norm

:Thanks for replies. The primary is ok. The sec s/b 260 ohms. It is 110 on one side and 420 on the other.
:

Check out this article, it might be helpful, especially Mod C. I recently had a similar problem with an interstage transformer:

http://www.philcoradio.com/tech/audio.htm

Neal - I will try your rejuvenation suggestion
Steve - thanks for the link. I have been following your thread