How to choose a replacement power transformer?

drwecki

New Member
Hello All,

My Zenith 95-1837 power transformer does not work. It is part of an old sterophonic tube console stereo that I'm trying to get to work.

Ok, so I want to buy a replacement transformer, but I don't quite get how to do it. I have the schematic and it gives me the following details of the power transformer

Primary: 117V @ .78A
Section 1: 720 VCT @ .105A
Section 2 5V @ 2amp
Section 3 6.3 V@ 1.8A


I'm on the EDCOR site, but they don't have a direct match.

Question 1 should I buy a 115V or 120V transformer?
Question 2 Should it be rated at 720 Volts (less or more)?
Question 3 A lot of these power transformers have the same voltage rating but different amp ratings. Should I buy more or less amps.

I get that the primary voltage is for the mains
I get that section 2 and 3 are for the tubes

After that, I have no idea what I'm doing.

The amd doesn't have to be EDCOR, but the website is the easiest for me to follow..Ha.

Cheers.
 
It'll be easiest if the mounting size is the same. There are several standard core sizes, and stack height varies too. Line voltage is often 120V or higher, better to choose 120V primary. Electrically, Hammond 273X and 274AX should do, both have a little margin over the original, and have a primary tapped for 115 or 125V (I'd use the latter). For Edcor, XPWR041 looks closest, 680V CT @ 120 mA. You can get a transformer with a higher current rating, but it will be larger and heavier, and might not fit. For voltage, I would go down a little, not up.

There's this used one at oldradioparts.com:
THORDRSN T-17R38 700 VCT @120ma, 5V 4A, 6.3VCT 4.7A, FIG 1,SOME SHORT WIRES 1 3 1/4 3 7/8 4 5/8 $18.00
 
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