Output Transformer Question

[lowell]

I guess make sure the 250pf cap is b/t the right lug of treble pot and then on the other side of the 250pf cap it should be connected the the slope resistor (100k) and plate (pin1) of first tube. double check that.

yes the nfb does reduce gain a bit, but allows for higher volume w/ cleaner tone.

[Bruce / Mission Amps]

Since it is canceling some of the signal,wouldn't that also lower the gain?I like the way my amp sounds now.Very lively.I think I'll leave the NFB out.
I still can't figure out why the treble pots aren't working.I have wired just as the AB763schematic suggests.

If the caps and the pots are good... what ever is left over, regardless of how impossible it seems to you now, is the truth... and that would be, you screwed up the wiring! ha ha

[lowell]

yeppers!

[ajeffcote]

OK,Saturday night I will have the time to get inside it again.But I have already looked it over three times.I will also record all the voltages and post them.
The NFB was causing the motorboat oscillation,because the signal was being inserted into the wrong place in the circuit,or the primary is wired in reverse,and was in phase instead of being out of phase,right?It's clear to me that I need to learn more about electrical theory in order to understand what is actually going on.
Again I want to thank you all for the guidance.

[kg]

ajc, reading some of these articles i have hosted on my site may help:

http://ken-gilbert.com/compensation-and-nfb
http://ken-gilbert.com/images/pdf/Feedback.pdf

feedback is one of those subjects that's pretty easy to get a big picture view of, but gets more and more odd as you dig deeper into it.

on a side note, i prefer an open loop output stage, though i've certainly heard lots of good amps with NFB.

ken

[ajeffcote]

I found the problem with my treble controls,or I at least fixed it.I checked and double checked and even tried wiring them in varying ways.It wasn't the wiring.It was overhead clearance between the chassis and the cabinet.The way I mounted the caps the treble cap and slope resistor junction was making contact with the foil backing rf shield,found under the upper cabinet.Apparently that offered enough of a ground for the higher frequencies to escape ,but not enough for the lower frequencies.At least that's my story and I'm sticking to it.
My PT is putting 354 AC into the rec,and I have 449Vdc coming out.444-446V on the 6V6 plates,and that's with them biased to about 11watts dissipation.I realize now that it is biased a little too hot,so I will reduce that to about 9.8watts.
Thanks for all of your help.
Aubrey

[lowell]

yeah!