The sunn Forum
Sunn Musical Equipment => Q & A => Topic started by: Lungs Music on January 29, 2008, 05:10:29 pm
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Hello, I have a '75 Model T Super (second generation) with a blown output transformer. My local amp tech says it will cost me several hundred dollars and many months of waiting to have Mercury Magnetics build me a new one. The benefit is that after they dissect and analyze mine, they will offer a replacement OT for the Model T in the future.
Has anyone sucessfully replaced the output transformer in a Model T? I've read posts on this forum about people researching the Hammond 1650T. Has anybody used this transformer? The specs say it is rated at 120 watts rms. Is that adequate for a 150 watt amp? I've found that tranformer for about $100. If it will work, I will probably go that route.
Thanks,
Jesse
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Hi there,I've had great success with Hammond trans.,both power and output types. I have used that particular trans. for replacement,but not in a Model T. Hammond trans. can be run up to their full ratings and they last forever. Still, having said that, I don't know if I'd use one in the T, I'd prob. look for a rewind job,good luck Mel.
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Thanks Mel, I think what I'll do is order the Hammond transformer and use that until I can afford the rewind from Mercury. I'd like to get this thing working right away. I found another source that said the 1650T can handle from 120-180 watts. I'll try that, if it doesn't work then I should only be out $100. I believe I also have to find another impedence selector switch, but that shouldn't be a problem.
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i ran in to this problem myself awhile back. there is no known "ready to drop in" aftermarket OT for a second gen model T. i was in touch with a guy that also said his company would re-wind mine, then have the specs to be able to build them for aftermarket use. can't remember the name now. have to check my email. but it was going to be rather pricey. upwards of 500 bucks. then as it turned out (thanks to joeaarthur walking me through testing and replacing a few parts) my OT wasn't blown at all. the tech i took it to didn't really know much to help me out. that's a whole other thread.......
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dynaco still makes the output trans that they used in the early model t's. Afterall, most sunn's were designed from dynakits.
Triode electronics carries them.
http://store.triodestore.com/a4dyoutr43oh.html
120$,
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Hi there,that's not the output trans. for a Model T, there isn't any 2 ohm winding and it's the "stand up" style not the "side mount" style that's in the T's.It'll prob. work in a 200S or a 2000S,though,good luck Mel.
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Hi there,that's not the output trans. for a Model T, there isn't any 2 ohm winding and it's the "stand up" style not the "side mount" style that's in the T's.It'll prob. work in a 200S or a 2000S,though,good luck Mel.
well yeah, other than the 2 ohm and the side mount. does anybody really run it at 2ohms anyway?
It would probably work if you jimmied it in and ignored the 2 ohm thing heh.
does anybody ACTUALLY make a direct replacement?
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I've looked,but haven't found anything that I would actually want to use or reccommend to anyone,Mel.
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as i have mentioned above. no. no one does make an aftermarket O.T. that is ready to drop in and go. at least in my research. there might just be, though. i'm actually surprised that there isn't one available at this point. you can't tell me that no one evr blew up a T and then decided not to replace the O.T. maybe sunn are indestructable.
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Hi there,that's not the output trans. for a Model T, there isn't any 2 ohm winding and it's the "stand up" style not the "side mount" style that's in the T's.It'll prob. work in a 200S or a 2000S,though,good luck Mel.
well yeah, other than the 2 ohm and the side mount. does anybody really run it at 2ohms anyway?
It would probably work if you jimmied it in and ignored the 2 ohm thing heh.
does anybody ACTUALLY make a direct replacement?
That A431 from Triode is a 60 watt transformer, designed for a pair of KT88/6550's, not a quad. It won't get the job done no matter what you do to it. I'd go with the MM repair job.
Big $$$, but sometimes you don't have other options.
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if i'm not mistaken, that transformer can be hooked up for 120 watts and 60 watts. :?
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is there an aftermarket for a first gen model t available?
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hey, just posting about the dynaco a431.
it is not a model t replacement at allllll. Its 60watts with 2 tubes, but you can use it at 120 watts with 4 tubes but the load on the tubes will be halved, and the impedance leads will change their value to 2,4,8 ohm taps. =/
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i have a first gen model t and today it sounded to me at least like the output transformer was saying goodbye to the land of the living. Lots of background crackling when playing the guitar, and after a while the amount of distortion when playing clean increased, although the volume didn't necessarily diminish. So what could it be, in other amps I have had, albeit they weren't not sunn amps, this has been the sign that the transformer is giving up the ghost, and compared to my second gen model t I used alongside it, it sounded so much quieter. Anyway, I took it to my amp guy here in london and he said that with regards to output transformers, that if a replacement has to be made that it might be possible to put an svt ampeg transformer in. So what do people think about that, is that really possible without it seriously effecting the quality of the amp? It seems to be that everybody has the same opinion, that getting the old transformer rewound is the only option.
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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. :oops:
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wouldn't it then sound like an ampeg?
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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.
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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.
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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.
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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.
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yeah I would like to see how you have done that