Ordering A Replacement Custom Spec Transformer?

[jfs322]

Hello All,

Quick question: I have an amp that I really love, and was thinking about ordering a second set of transformers to keep in storage for if anything were to go on the amp (I suppose the transformers would be the hardest part to replace?). Apparently the transformers are custom spec (i.e. item number) unique to this amp company. Is it possible to call up the transformer company and order a replacement set, or will the manufacturer only sell the amp company? What's the best way to go about getting replacement custom spec transformers?

Thanks!

[sirbergs]

I would think the tranny manufacturer has a contract to only sell those trannies to that amp maker. I’d start with the amp maker.


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[talbany]

I would think the tranny manufacturer has a contract to only sell those trannies to that amp maker. I’d start with the amp maker.


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Yes this is true.
The amp company works out the specs on the X-former from the manufacturer. A deal for a certain number is usually met, the amp company assigns the part or model number whereby only the amp manufacturer is able to order the part with that model number on it. The terms of the deal between the two is subsequent to the demands of the part maker. However! if you know or can get the specs of your existing transformer you can easily match it with a generic replacement from another manufacturer and with most power transformers in tube amps not going to notice much if any change in performance with the replacement.Again as long as you keep tight tolerances with the replacement.
Some companies (like Heybour) might even wind you a custom for you for a small upcharge. That's generally how it works.

BTW. Some X-former companies take an existing transformer that they might sell to another amp company which is basically the same transformer, change the part number and assign it to another amp company. This is done all the time. So the only thing that has changed is the number.Sometimes it involves a contract sometimes it's just a verbal agreement or a handshake. This usually depends on the type of part and how far they are willing to go to protect there designs patents how many they order etc etc

Tony

[Phil_S]

I'm going to discourage you on both trannys.

I wouldn't bother with a power transformer. A close replacement is good enough that you aren't likely to notice any difference at all. Mostly, a PT is all about output volts and mA capacity. IMO, the main concern would be about getting one that offers a similar amount of sag or stiffness in that particular circuit. It shouldn't be hard to find one unless there is something unusual about it.

What is your personal experience on actually blowing an output transformer? If you know that you are going to need it, by all means you should have a replacement on-hand. If your experience is that you've never blown an OT or the instance was rare and under unusual conditions, you don't need to go to the trouble of getting one. When/if it blows, if you can't obtain an original replacement, you send it off to a company like Heyboer or Mercury Magnetics or a local winder if you've got one and ask them to clone it or rewind it. Sure, it won't be cheap. They will unwind it and rewind to original spec using the same lamination set. It should be just like new when they are done. And you won't be tying up your money in a piece you are likely to never use.

[jfs322]

Gotcha, thanks. I thought about just waiting until (or if it ever) blows and sending it a company like Mercury to have them rewind it back to original spec. However, can they determine the original specs if the transformer is blown? Would they still be able to get appropriate readings from it?

[Charlie Wilson]

Sorry to be that guy but is there a reason the you have not told us who manufactured the amp and what model? Also, if that manufacturer is not Dumble or a Dumble reproduction company this post does not belong in the Dumble Discussion section.
CW

[pompeiisneaks]

Sorry to be that guy but is there a reason the you have not told us who manufactured the amp and what model? Also, if that manufacturer is not Dumble or a Dumble reproduction company this post does not belong in the Dumble Discussion section.
CW

agreed, moved to technical discussion.

~Phil

[R.G.]

Gotcha, thanks. I thought about just waiting until (or if it ever) blows and sending it a company like Mercury to have them rewind it back to original spec. However, can they determine the original specs if the transformer is blown? Would they still be able to get appropriate readings from it?

Transformers are at the same time maddeningly complex and blindingly simple.

The blindlingly simple part is that a transformer's operation depends only on the core material type (and there are only a few of these that are reasonably choices), the lamination size (which is standardized into a number of shapes) a stack height of the laminations, and a set of winding instructions, which goes like: wind m turns of wire size A, then wind n turns of wire size B, then another m turns of size A, then ...

The only real complexity is hidden. The core material has a huge effect on the results, but there aren't many to pick from. The frequency performance depends on the physical location of every turn of wire relative to every other turn of wire inside the coils.

So yes, a transformer repro place can wind up a nearly exact replacement from only a dead transformer. All they have to get right is the core materials, number of turns, and how those turns are arranged inside the coil. The other stuff, the insulation types and so on, only matter to the temperature performance of the trannie. Insulation is as transparent as air to a magnetic field.

You're no doubt thinking about how the amp designer specified impedance ratios, leakage inductance, frequency response widths, and so on. They may have made a long list of those, but the guy who designed the transformer reduced all that to core selection and a winding table.