What are indications of output transformer going bad??

[Wrongdog]

I have a1965 Deluxe reverb and it it is not sounding good at all when pushed 5 plus on the volume on either channel.

When I bias it all is good idle with matched 6v6 tubes. If a OT is going bad they usually don't bias properly, right? Idle, the bias is fine (30/29ish) but when played at 6 with bias meter in place one tube bias swings much higher than the other - like 80 vs 50. Is that an indicator of a OT going bad??

All the usual suspect, out of spec components have been replaced, including filter caps, some coupling caps, some mixing caps, some bypass caps and some +10% resistors. Voltages all are within 5% of spec, tubes tested and subbed etc. OT is NOT running hot and no fuse issues. It just sounds raspy and the harmonic overtones after the (mostly mid) notes blossom just ain't "Deluxe Reverby".

I think I am trying to keep this thing original at the expense of having it not sound good and that is kind of dumb!! Thanks if you can help!

[Amp Kat]

Transformers don't usually half ass screw up. They are either all on or all off with the rare exception if the short halfway in the winding causing a very faint sound. If you ohm out the primary leads and they read equal on both sides from the Center Tap the tranny is likely good. Most Fender OT's use red for CT and brown and blue for the outer windings.

[Jazz P Bass]

Why don't you try reversing the output tube positions & see if that 80 vs 50 measurement follows the tube.
You may just have a weak tube.

[Enzo]

There is no "usually." First, they usually don;t fail, they are way down the list of failures. But more importaqnt, failures are not generic. Asking what goes wrong when they fail is like what goes wrong with a car when it fails. Who knows, transmission? Engine? Rear axle? Water pump? Electrics?

An OT can be really screwed and yet the amp will set bias OK.

Your tubes bias up at idle? Good, that is what they are supposed to do. As soon as you start to play, you are no longer measuring bias, you are simply measuring tube current. If they are widely different, it could be the tubes or the circuit. DO what Jazz said and swap them. Did the imbalance change sides?

Could be your phase inverter is not driving both sides, and that would not only affect current but it will have a large impact on sound quality.

It is really not likely the transformer.