Advice for swapping output transformer in Koch Twintone

[kka]

I diagnosed a bad OT on my customer's vintage Twintone (50W). I had temp. hooked up a new OT for a Crate VC-120 and it sounds absolutely great. I wonder if I could just install this OT without running into any problems. This OT delivers so much more headroom and punch than the original.

Of course I would have to drill new holes into chassis. I'm only wondering about internal circuit issues.

Thanks for the help !

[Steve Conner]

Usually no big deal to swap OTs between amps of a similar power rating. However 120W is a bit of a stretch from 50W. It will work, but you'll be loading the power tubes wrongly unless you move all the secondary taps "up one" (connect a 16 ohm load to the 8 ohm tap etc)

Most tube output stages can tolerate a 2:1 mismatch, so you may get away with it, but I'd rather use a 50W OT.

[J M Fahey]

This OT delivers so much more headroom and punch than the original.

Of course, because the new one is healthy and the old one is sick.
But as Steve says, if you properly match impedance (which is iffy with a 120W transformer, even by "miswiring" it) you'll get even better results.

Anyway what you did is fine to confirm diagnostic

[kka]

Thank you both. I did research and do understand OT calculations much better now ;-)