5F6A won't break up

[el_fela]

Well, it seems the problem is not V2.
I simply took off the second tube out, disconnected the tone controls, and the connected the output of the volume pot to V3 pin2 (using a cap).
The clean sound is clean, but when it starts to overdrive (near full volume) it sounds like crap. It sounds like an overdrive, but a crappy one.

¿Where should I look now?

***EDIT****

I have a question: of the 3 wires from the PT that go to ground , there is one for the 50V bias supply . Of the 2 remaining, if I disconnect one, nothing happens, but if I disconnect the other, the tension of the filaments rises above 150V. What about that? Is this normal??

[loudthud]

I have a question: of the 3 wires from the PT that go to ground , there is one for the 50V bias supply . Of the 2 remaining, if I disconnect one, nothing happens, but if I disconnect the other, the tension of the filaments rises above 150V. What about that? Is this normal??

This is most likely leakage from V2, the high voltage on the cathode of the follower. Have you tried swapping that tube out? There were some tubes with "sprial" heaters that were realy bad for this. Sovtec or EH IIRC.

[el_fela]

Thanks loudthud, I tried swapping the tube, but no luck. Im using tung sol 12ax7 for V2 and V3 and one EH 12ay7 for V1.

If I disconnect the HV center tap, there shouldnt be any more HV, right? Because I disconnected all three wires from the PT that were grounded but I still get HV.
IS that supposed to be OK? MAybe there is one less wire ? I should have 1 from the electrostatic screen, another one for the heaters, one more for the 50v bias ground and another from the HV center tap, and i only have 3 wires from the PT to ground....

[loudthud]

I'm not sure which transformer you have. Most transformers that follow the way Fender did it do not have a separate ground for the bias supply. If you disconnect the HV center tap but leave the bias tap connected on one of those, you'll get a weird result possibly blowing up your bias supply. Unless you have a transformer like the Ceriatone (with a separate winding for bias), disconnecting the HV center tap will disturb the bias supply. The bias supply needs to be active before you switch on the B+ with the standby switch to prevent damage to the output tubes. Marshall had this problem on some of their early models.

[el_fela]

maybe its a little late, but thanks for your reply!

I installed a pair of weber signature alnico 10S and the amp came to life. I couldnt believe how big the improvement in sound was. It sounded much more compressed but rich, and the highs became super sweet.

Not being able to make the sound acceptable after a year of circuit tweaking, I abandoned the proyect and built a Deluxe Reverb.
Hope this thread is usefull to someone else. Thanks everyone!

[Casey4s]

Maybe you should disassemble the 5F6A and rebuild from scratch. Personally I would use the Fender schematics etc. I built a DIY 5F6A in 1998-99 and it worked perfectly but I could never get mine to "overdrive" without incredible volume. I finally installed a post PI master volume and gain and everything changed, I can get all the overdrive I can handle and still get clean tones. I just think those amps have to be really pushed to get that OD tone otherwise.

Just my opinion...

Good luck to you Sir