The PHILCO Phorum
37-610 audio output transformer - Printable Version

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37-610 audio output transformer - RGallahue - 12-29-2025

Have a 37-610 with an open audio output transformer.  The field coil is fine and the speaker itself is good, so would like to keep that intact.  Looked in the library for the 32-7019, no info there but in looking at some previous posts, looks like anything that would work for the 6F6 or 42 should work as a replacement.  

Just wondering if anyone here had replaced this particular audio transformer only before and might have some knowledge to share before I wind up purchasing a very expensive Hammond unit...

BTW, I did look to see it this was a break I could get to, and the answer is no.  

Thanks,

RE: 37-610 audio output transformer - Arran - 12-29-2025

I think that it is a fairly straightforward single ended, pentode based, audio output stage, so you don't really need an expensive Hammond unit. in a pinch you can use an output transformer from an AC/DC set, or even a six volt filament transformer, or a line matching audio transformer. if you need something larger. one off of a junk set with a 6F6/42/6V6/6AQ5 would also be a match. I believe that AES, or whatever they call themselves now, sells a generic audio output transformer made in Mexico, that is cheaper then the Hammond brand one.
You could also have a go at repairing the original, you may be lucky and find that one of the leads broke off internally.
Regards
Arran

RE: 37-610 audio output transformer - RodB - 12-29-2025

I'm using a Bogen T725 line matching transformer in my 37-630 with single ended 6F6 on the bench right now and it works just fine. Maybe $12 + shipping.

RE: 37-610 audio output transformer - RGallahue - 12-30-2025

Thanks, Gents!

I had not thought about the line matching transformer idea, and it certainly is a better bet financially.  I am going to order one and give it a try.  I did find a good worksheet out there listing calculated impedance values.

RodB, just out of curiosity, what configuration of wires were you using on the primary side?

Thanks again!

RE: 37-610 audio output transformer - RodB - 12-30-2025

Richard, I'm using black, as the common and purple. Blue is the lower impedance at 5K and purple is the higher at 10K. They seem to work equally, although I haven't pushed a signal through the tube to measure which one produces the most output. I did it by ear. The speaker output wires are the 2 that are the same color coming from the same side of the transformer. One transformer I have they are pink and the other they are black. If in doubt measure the resistance, should be around 2-3 ohms. I have used this transformer at least six times and it has worked well. There's another one that's identical except it handles a little more power for those 6L6s and EL84s, the Bogen T-72510.

RE: 37-610 audio output transformer - MrFixr55 - 12-30-2025

There is a theory that Line matching transformers cannot handle the DC component, but several Phorum members use them as output transformers with no issue.

For 42, 2A5 and 6F6 (all the same tube except for basing and, in the case of the 2A5, heater voltage, single ended plate resistance (transformer primary impedance) is 7,000 Ohms at either 250 or 285V. 6V6, 6BQ5 and 6AQ5 are around 5K Ohm. AA5 Output tubes (25L6, 35L6, 50L6, 50C5, etc. are around 2.5K

RE: 37-610 audio output transformer - RGallahue - 01-18-2026

To all,

Sorry to take so long to report back, but I finally got the Bogen in here and hooked up, and it works very well.  I have not checked whether or not the lower or higher impedance works better, but will get to that eventually. Cannot really tell a difference by ear.

I can understand the DC issue, but this transformer does not appear to be bothered by it in the least.  I think I will turn to these first before I go with Hammond again. 

I want to thank you all for the tip and your replies. That's what makes the Philco Phorum great.

Regards,

RE: 37-610 audio output transformer - RodB - 01-19-2026

If it exists, you might see some distortion, or possibly hear it, at higher frequencies. Some time ago I fed 1KHz to the radio and checked the output level to the speaker with one tap then the other and there was a very slight difference. So I've been using my ears to decide. I'm really glad you're happy with the result.