Heathkit potted power transformer question

[Boris_The_Blade]

I recently got a heathkit W4-AM amplifier on ebay, but it does not have an original power transformer. I kind of want one for aesthetic reasons. I looked around for one, but to no avail. I was wondering if anyone knows if there are similar heathkit PTs. After looking around, I can see from schematics that the W5 and A9 have similar power supply topologies and ratings, but I'm not sure if they are mechanically the same. I would assume so, but assuming usually turns ya into the first three letters... Anyone have experience with this or have a W4 and another to compare?? I probly won't find a W5 available for this unless the rest of the parts are junk on it for some reason (i.e. blown OT), but the A9's come around every once in a while for not too much...

thanks

[JohnAtwood]

The potted power transformers in the Heath W-3 and W-4 amplifiers were notoriously unreliable. My dad replaced the transformer in our Heathkit W-3 amp sometime in the late 1950s (he bought it in 1955). As a result, there are not too many working originals around. The W-5 transformer has substantially higher B+ voltage, which would be a problem. If you really want originality, melt the tar out of a burned-out transformer, and put the replacement inside. Messy, but should work.

- John Atwood

[Boris_The_Blade]

Thanks John,

Just noticed the W5 voltages...yea definitely wouldn't work. It was the W2 I was thinking of. Well, maybe I'll look into repotting old transformers with better ones... I've potted things before at my old job. I'll have to bake the old ones out. Now to post a note at the trading post for old heath transformers... You wouldn't happen to have your old one still around would you? I didn't get the old one with my purchase, and I don't think the seller would know where it is. I've looked but had no success finding similar shells to the heathkit.

This seems like a lot of work, but for me I think it would be worth it.

thanks again,
micah

[JohnAtwood]

I might have an empty can of the right size (maybe even with the correct Heathkit part number stamped on it). I bought some old transformer cans a long time ago that had been emptied of their contents. I have to check in my storage unit and see. Wait a day or two.

- John

[Boris_The_Blade]

New light on an old topic...

I came into another W4 that had a bad power transformer. I used a blow torch to melt the bad transformer out of the can, then potted a stancor PC8411 in it with clear epoxy resin - worked like a charm. The stancor never got real warm in normal operation, so I am not worried about heat with the epoxy. I've run it for a few weeks now, maybe several hours straight at a time with no problems. I'm mentioning this, because I figured other people have the same problems and this info might help out. If anyone wants to know more, let me know and I'd be glad to give materials and instructions...or I might even be willing to do it for charge (grad student trying to fund his hobbies here :-) I can also sand/prime/paint the new can to look very nice.

- btb