Negative feedback problem Help

[Helmholtz]

It looks as same. Reversing the PI outputs didn.t put the signals in phase.

Sorry, that can't be.
Either a wiring or a measuring error.Where do you ground the scope probe when scoping the output?

Scope the upper power tubes' grid signal together with amp input signal to see if you actually reversed the phase by swapping the PI outputs.
I suspect you're doing 2 phase reversals at the same time.

[catalin gramada]

Helm, you did it damn right!!! Actually the input wiring didn't shift the phase. It was a wiring mistake I didn.t saw it. I have to work a litle bit and come in back with results. Thanks !!!

[catalin gramada]

And Yes !!! Reversing input phase and everything comes as normal should be . Thank You guys! Helm you rock, Thanks man !

[Helmholtz]

Wow, so many likes!
Thanks for appreciation.

Now I'm really curious to know what exactly went wrong. Maybe someone (including me) could learn something.

[catalin gramada]

It was a confused wiring layout I did.... I switched and reswitched the wiring to bias supply thinking the wiring from plates to inputs power grids was switched aso...which was not the case. Sometimes cannot see something was in front of my eyes...and was convinced the phase was switched but never checked...I spent a whole days lurking around but need it someone like you to pointed right. Thank You.

[catalin gramada]

Looks pretty nice, taking an consideration a crappy matched toasted kt88 quad...
8db nfb was applied. 256W rms into 8 ohm load
85 w max plate power dissipation per tube is a little bit too much. Screens are in relative safe region with no more than 10w with 1k stoppers. May I consider 1.9k is a serious load for a quad at 600v around, but have a lot of character...perhaps...