W-5 power transformer replacement?

bear-hifi

Well-Known Member
I need to replace the power trany for a heathkit w-5 and I was thinking about buying two of these. However they are not the exacted numbers and I was wondering if they would work?
P-T279X
2006 Catalog
page 26

TRANSFORMER, POWER, HAMMOND, 425-0-425 V, 150 mA
• Primary 115 VAC, 60 Hz.
• Secondary DC current measured with cap. input filter, full wave (two diode) C.T., rectifier circuit.
• Enclosed, 4 hole chassis mount.
• Minimum 6" long leads.
• Class A insulation (105 degrees C).
• Hi-Pot test of 2,000 V RMS.
• Conservative designs - CSA certified (# LR3902).

Secondary: 425-0-425 V, 150 mA
Filament winding 1: 5 V, 3 A
Filament winding 2: 6.3 V, 5 A
Mounting centers: 2.5" x 2.69" vertical mount
Weight: 6 lbs. $68.95
Qty




The numbers (on the new Hammond transformer) are very close to the specs of the original Heathkit W5M which are below. Differences in RED.

Secondary: 455-0-455 V, 140 mA
Filament winding 1: 5 V, 3 A
Filament winding 2: 6.3 V, 4 A
 
Lower B+ voltage will cost a little output power, not much. Higher filament rating is GOOD news.

Many of these failed due to a short at rectifier socket - good idea to replace it with a ceramic one.
 
Remember that when the W-5M was designed, line voltage was 110 - 115 VAC, whereas it is closer to 120 - 125 these days. You're probably going to be right in the ballpark with your B+.

Edit: Wait a minute, did I get that backwards? I know I have read that it is unwise to use anything other than (the original) 5R4 rectifier in a W-5M these days, as other rectifiers have lower forward voltage drop and can result in too-high B+ when using the the original transformer on today's line voltages...now that I think about it, your B+ may be lower with the Hammond, you could safely experiment with another rectifier though.
 
Last edited:
Hey-Hey!!!,
Wow! a W5 with a dead PT instead of output. It must be a 16458.

Getting a PT with lower HV and adequate filament amperage looks like a good idea to me. Nothing about the W5 circuit requires a lot of B+. 400-0-400 should be quite enough, even with a 5R4.
cheers,
Douglas
 
As an aside, I have a Heathkit service note somewhere that lists the Stancor PC or PM-8412 as the recommended replacement. Believe that one was 400-0-400 @ 200mA.


bear-hifi said:
I need to replace the power trany for a heathkit w-5 and I was thinking about buying two of these. However they are not the exacted numbers and I was wondering if they would work?
P-T279X
2006 Catalog
page 26

TRANSFORMER, POWER, HAMMOND, 425-0-425 V, 150 mA
• Primary 115 VAC, 60 Hz.
• Secondary DC current measured with cap. input filter, full wave (two diode) C.T., rectifier circuit.
• Enclosed, 4 hole chassis mount.
• Minimum 6" long leads.
• Class A insulation (105 degrees C).
• Hi-Pot test of 2,000 V RMS.
• Conservative designs - CSA certified (# LR3902).

Secondary: 425-0-425 V, 150 mA
Filament winding 1: 5 V, 3 A
Filament winding 2: 6.3 V, 5 A
Mounting centers: 2.5" x 2.69" vertical mount
Weight: 6 lbs. $68.95
Qty




The numbers (on the new Hammond transformer) are very close to the specs of the original Heathkit W5M which are below. Differences in RED.

Secondary: 455-0-455 V, 140 mA
Filament winding 1: 5 V, 3 A
Filament winding 2: 6.3 V, 4 A
 
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