[percyjd]

Acquired a Westinghouse WR-258 radio that looks like it will need a new power transformer.  Found a large pool of black wax under the chassis and when I opened the clam shells it's apparent that the unit was severely overheated at some point in the past. Both the primary and secondary sides showed continuity, but it really looks toasted. I've repaired a few radios in the past, but never had to replace a transformer. 
 
I've found a couple of Hammond replacements, but not sure which would be the best fit as they don't match exactly.  I've included the specs for the current transformer and a couple of available replacements.  Any advice on a suitable replacement model would be greatly appreciated.
 
Since I couldn't locate the specs for the original Westinghouse power transformer, I looked up the replacement using a Thordarson catalog and found the following model listed:

T-22R00: 117v/50-60Hz, Plate 500v CT @ 40ma, 5v @ 2a, 6.3v @ 2.0a
 
Hammond 270X: 115v/60Hz, 480V C.T. @ 46ma., 5V @ 2A, 6.3V @ 1.5A
Hammond 270CAX: 117v/50-60Hz, 500V C.T. @ 81ma., 5V @ 2A, 6.3V @ 2.5A


Here are the schematics for the WR-258

M0024379.pdf Size: 54.21 KB  Downloads: 139

[MrFixr55]

Hi PercyJD,

Does the JD stand for Juris Doctor?

If so, a Disclaimer that the following information is given as a courtesy, and the user is fully and solely responsible for verifying the suitability of this information for use.

Certainly, the 270CAX should work if the Thordarson specs are correct. It may be cheaper to buy a used transformer from eBay, as the Hammond is not going to be cheap

The circuit in this diagram is very typical of other radios of this vintage. I would say that any transformer out of many of these radios would work as long as the donor radio has a field coil type speaker, has 5 tubes and the rectifier is an 80, 5Y3, 5W4 or 5Y4, but the Field Coil resistance of your radio, at 1600 Ohm is rather high. Most radios of this vintage have field coil resistances of about 000 Ohm to 1200 Ohm. The only variable is whether the transformer has an isolated 5V winding, is for a 5 tube radio and what is the High Voltage secondary output. One from a GE G52 or G56 would work. The tubes are almost the same and the field coil is within 200 Ohm of yours. The goal is to have a B+ reading at the Audio Output transformer of around 250V. The B+ voltage into the speaker field coil is usually 50V - 100V higher

One thing you can try is the "Dim Bulb" test. Place a lamp socket in series with the radio power cord. Place a 60Watt bulb in the socket. REMOVE ALL TUBES!

Carefully power up the radio. If the bulb is dim, continue. If the bulb is bright, or arcing occurs, the transformer is seriously shorted. STOP and SHUT DOWN! Measure across the power transformer high voltage secondary. CAUTION!! High voltage!! risk of dangerous or deadly electric shock! If you have no experience working with high voltage, seek help.

If you have experience with high voltage / high current, perform the above measurement across the HV secondary (to the plate connections of the rectifier. Record the voltage. if within 20% of 500V, the Hammond will do. Measure between each leg of the secondary and the center tap. The voltages should be half the voltage across the 2 legs and be within 10% of each other. If seriously off, your short is there.

Sometimes, a transformer just fails. Other times, there is a cause. A shorted rectifier or shorted capacitors will do this.

In addition to replacing the transformer, replace all paper and electrolytic capacitors and check the rectifier tube. Yours is a 5Y4. a 5Y3 is NOT a direct replacement. The socket has to be rewired.

Add a 1 Amp fast fuse between the radio's power switch and the transformer primary. To prevent a shorted rectifier from burning out a transformer, I usually place 1N4007 silicon diodes in series between each plate pin on the rectifier socket and the transformer HV secondary, with the anode connected to the transformer wire and the cathode connected to the plate pin of the tube socket. do this for both transformer connections to the rectifier plates.

Good luck.

[percyjd]

MrFixr55,

Thanks for the detailed reply. I conducted the dim bulb test today on the transformer which I had already pulled from the radio. According to my measurements, the high voltage secondary was only outputting 273 volts, with each leg unevenly split between 52v and 220v. The bulb glow remained fairly dim, but the transformer heated up pretty quickly (no smoke, sparks, etc.). I'm assuming the secondary is shorted somewhere.

I'll start scrounging for a replacement. The Hammond 270CAX will work, but the cost is higher and it doesn't lay flat like the original.

Already planned to add a fuse. Hadn't considered adding the diodes, but something to think about.

Thanks again.

[MrFixr55]

Hi PercyJD,

Yes, that transformer is definitely toast.

In a strange twist of fate, at the beginning of radio, Westinghouse, GE and Wireless Specialty built all RCA Radios, as at the time RCA was a marketing company.  After RCA acquired Victor Talking Machine (of Victrola fame), who was already building radios, RCA became a manufacturer and was building al GE and Westinghouse radios till about 1935.  Westinghouse ewas slow in building their own radios after that and until the 40s, Westinghouse Radios were built by such companies as American Bosch and even Emerson. (I have one of each), as well as some of their own.

It may take time but if you look on eBay, you may find a suitable used replacement.  Look for one from a 5 Tube radio that uses either an 80 or 6Y3 rectifier amd output tubes such as 41, 42, 6K6, 6F6 or 6V6 and 3 0r more other tubes, and had an electromagnet dynamic speaker.

[Arran]

Try looking on the AES website under guitar amp power transformers, more of those are horizontal mounted then the standard Hammond fare, they also seem to be cheaper (volume sales I guess?) Most power transformers for radios had a 350-0-350 volt H.V secondary, and a 2 amp 5 volt winding for the rectifier tube, to figure out what the 6.3 volt heater winding needs add up the current draw of the tubes in the set, most are 300 ma each, plus whatever the audio output tube draws 800 ma to 1.2 amps depending on type.
Regards
Arran