Tweed Gibson Vanguard - output transformer replacement.

sysy

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Jul 30, 2020
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Europe
Hello all,

First - some context - I am a budding amateur, and nothing more. Have built some kits, done some basic repair work and trouble shooting on my amps, but this is the most involved restoration project I have ever taken on. With that being said, I'd like to take the work on myself and see it as a learning experience.

I have recently purchased a 1959 Gibson Ga-77 (Vanguard) in working but not ideal condition. As the amp stands right now - it's a ton quieter than I would assume a push pull 5881/6l6 amp to be and is maybe a tad bright for my own personal dark leaning tastes, but still sounds very cool. I am going to with hold judgement on it, and first fix it up, and then use it for a while to get a feel for what it does.

A lot of work has been done on the amp over the years - all filter caps and some coupling caps replaced. But I see no reason to doubt that what's in there now is working well.

The most glaringly non original thing about this amp is the output transformer. The original is long gone and had been replaced with a cylindrical transformer (Tabuchi brand) that is mounted on the side of the cabinet . I know nothing of its specs but I think its worth spending a little money on a new output transformer that is more appropriate - it's bugging me as it is.

Does anyone have an idea of what the original specs on output transformers on these amps was? The way I see it, I can either get something along the lines of a tweed pro replacement (6k primary impedance) - or a pro reverb replacement with an 8ohm tap (4k primary impedance). Considering that the original rather low wattage p15p is still in the amp 60 years on, I am guessing most likely the thing never put out its full potential, so I am leaning towards the 6k primary. But my understanding of how output transformers work and how they are chosen for a given amp is still very basic, so any tips are appreciated.


Thank you all.
 

Jon Snell

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Wally

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Yes, there are less expensive options; but ime Mercury Magnetics will produce an OT built to original specs.

 

uriah1

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Yep. I had a mercury mag done to my old Gibby. Wish I still had it.
I think I had a choke PT,OT,choke add.
 




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