Model T output transformer options

[the_bleeding]

theres 3 things you can do.

1. Get the transformer rewound

2. get a custom transformer made by somebody

3. get a transformer off the market that is betwenn 120 and 150 watts with ultralinear taps. Though on this route, chances are that the transformer wont have a 2 ohm tap.


personally, i wouldnt get the SVT transformer, those things are made to push out 300 watts and you're probably looking for 150 max to keep it close to original. i dunno man, its a tought choice. 

[cromag]

wouldn't it then sound like an ampeg?

[pombagira]

well apparently it would change the sound but not too much, or that is what I have been told, as it stands it looks like it is the not the transformer that has given up the will to live. New valves were put in, electro-harmonix 6550, and they were apparently crippling the ampage, reducing it to 112 watts rather than 150. In fact when the old groove tubes were put back in it was registering 180 watt output. The reasons for why this might be are far beyond my technical know how. Another weird thing about this is that the same valves were put into my other second gen model t and they worked fine. So was it in the end a batch of faulty valves...it could have been. The story isn't quite over yet there are still some further checks that need to be made before I get the amp back. Just relieved at this moment in time that the problem didn't reside with the output transformer. Has there been any progress in getting a manufacturer to make off the shelf replacements? I was also told that even a svt 300 watt output transformer if used to replace the sunn model t transformer would not push  out 300 but would be regulated so it would only provide what the amp needed. If this is really the case, this may provide a cheaper alternative to getting the transformer rewound, which here in the UK would have cost me a small fortune. In the same region as actually buying another model t from the states. 

[mckinnon audio]

  Hi there,the wattage ratings on trans. refers to the amount of power the trans. can handle from the amp.the trans. doesn't make power,so a 300 watt tranny will work fine with 150 watts feeding it,there's no self regulating going on,the trans. is simply working at 50% capacity.As far as SVT tranny's go,the really old ones,(from the era of the hard wired 4-pin XLR spkr. conn.) had 2 seperate 150 watt taps,on for the 4 pin XLR and one for the ext. spkr.,the new ones have a 300 watt winding.If you could find an old one you might be able to make it fit,rather large though,good luck Mel.

[pombagira]

well as it turns out all is well on the amp front. It just so happens that the 6550 electro-harmonix valves were faulty. They were knocking out only 112 watts whereas the old American vintage tubes that had been in it were getting close to 200 watts.... and they weren't balanced!!! So  although I had to settle for modern valves that aren't as great as those old ones, it comes as a relief to have no imminent rewiring.   However, I have been in contact with mercury magnetics in chatsworth CA and their technician is very keen to get hold of one of these old sunn model t transformers so they can go into production. If there is anyone on the forum who needs to have a output transformer replaced then you should contact them, they will give you a really great deal on replacing your old transformer if they can use yours as the model. Its certainly an interesting proposal and one that could put everyone's mind at rest. I have to say that I have been panicking that one of my very precious model t's would be out of commission for some considerable time. 

[Lungs Music]

Well, I ended up using the Hammond 1650T and it has been working great for the last few weeks. Of course I had to make an aluminum adaptor plate so It could bolt in, but otherwise it was a very easy installation. I didn't have to drill any holes in the chassis. I bought an impedance selector switch from Antique Electronics. It comes prewired for the transformer and works quite well. I'll give Mercury a call and see if they would give me a deal on having the old one rewound, but I'm in no hurry.  I can post a picture of the transformer mounted if anybody is interested.

[pombagira]

yeah I would like to see how you have done that