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output transformer for a heathkit w5m

cocobolo95

cocobolo95

New Member
I just bought a heathkit w5m that is missing the output transformer. Does anyone know of a good readily available substitute for the peerless 16458, which amp originally came with.

I would also like to know if substituting a higher wattage output transformer with the same 10K ohm plate resistance would harm the amp.

Thanks in advance for the info.
 
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16458 are hard to find.

I'll get Gary's one: it's a fresh rewound and if you tweak your W5M cathode resistor to not run hot, this transformer will do well.
 
If you are patient they turn up fairly often on epray. But the price is high and it seems almost half the price of a complete amp. Having one rewound is done quite often but that is almost as much as the price of a used trans. Rewinding has the issue of somewhat different materials 1960s era vs currently available copper. Some guys swear that the copper made back then (virgin copper, not recycled) was better. I think that many buy 3 W5s to get 2 good ones.
 
Is it reasonable to assume the 16309s still alive do not harbor the self destructive flaws of the others? I've read the problem with them was probably air pockets in the pots that lead to condensation borne failure. So by now if it's functioning, it will probably continue to do so, no?
 
P1040424.jpg P1040426.jpg 16309's were considered an improvement over 16458's. They have a few laminations made of nickel in the middle instead of the normal transformer iron. I have a few pictures someplace I will try to find. Supposedly flatter response, as told to me by a Heath engineer many (30+) years ago. Notice the cap!
 
stanko, very interesting indeed.

Is that the peerless 16458 ? Is that transformer ok, or faulty? Can you identify where the cap is connected and its value and voltage rating?

Edit: doh, the text is offset - its a 16309.
 
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trobbins said:
stanko, very interesting indeed.

Is that the peerless 16458 ? Is that transformer ok, or faulty? Can you identify where the cap is connected and its value and voltage rating?

Edit: doh, the text is offset - its a 16309.
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I can't identify either, I've rewound many transformers, but never a 16309. My bad memory tells me the cap was across the 16 ohm taps for high frequency damping.
 
Here's me rewinding a power transformer. Output transformers are many times "interwoven", the primary and secondary windings are interwoven like shuffling cards of two piles, if that makes sense. Output transformers are very difficult to rewind if one interweaves the primary and secondary. I wonder if the transformer rewinders interweave, because it would seem their prices are too cheap if they do. It's a lot of extra work to interweave.
http://audiokarma.org/forums/index.php?threads/scott-130-power-transformer-fix-revised.501157/
 
Superampman said:
But didn't the 16458 appear as a later version?
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FWIW, everything I've read supports the 16458 as the later version. While technically a very good OPT, the 309 was failure prone and the 458 was Heath's response to the situation.

The OPT in the posted pic is the 309 with the nickel lams in the center. Legend has it that the 458 had a conventional core. Also, a rewinder told me the cap seen in the 309 pic was placed across primary CT and one of the anode windings to equalize stray capacitance either side of CT. Cap was custom "selected" at time of mfg and was 1000V silver/mica. Never had one apart myself so can't verify any of this. However, it does make some sense: EICO did almost exactly the same thing with the OPTs in their higher end offerings except that the cap was typically ceramic and external to the OPT.
 
Here's a link to an article written by a guy named Charlie Kittleson written for Vacuum Tube Valley. In it he states the 16458's were the early for the W5M and the 16309's were the later ones. Charlie was well known in tube audio circles back in the 1970's, 80's, 90's, etc.
http://dalmura.com.au/projects/VTV02 extract.pdf
 
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Interesting. Thanks for sharing.

Underrated leaky coupling caps contributed to the bad reputation of the OT by disturbing the output tubes, IMO.
 
Brice said:
Interesting. Thanks for sharing.

Underrated leaky coupling caps contributed to the bad reputation of the OT by disturbing the output tubes, IMO.
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I agree with you 100%
Brice said:
Interesting. Thanks for sharing.

Underrated leaky coupling caps contributed to the bad reputation of the OT by disturbing the output tubes, IMO.
Click to expand...
I agree. I screwed this post up somehow, my apologies.
 
My take is that the PT which puts out about 1000v on the secondary is designed for choke input filter. A better design is a 2 choke LCLC power supply with a 5ar4 rectifier. The 5ar4 rectifier in a LCLC ps should be able to bring the voltage surge to less than 500v probably around 450v instead of close to 700v which is how a stock unit is operating. The high voltage surge stresses all the components from caps to wiring insulation. This causes an inordinate amount of failures which makes the w5 an unreliable amp in stock condition.
I am planning to take some transformer measurements and play with the power supply in PSUD2 to see what the original is compared to other designs.
 
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