BIAS Deluxe Reverb High B+ AB763

[7xa12]

What BIAS setting would you recommend for fender deluxe with 450V on plates ? ( JJ 6v6s tubes)
what is a safe minimal and max settings?
I set it at 16ma.
14/450 X 0.7 =0.021 - 21ma
my screen grid voltage tends to be higher than plates voltage (about 10V max) Is it a problem?

[7xa12]

I found some info that max is 16ma.

[Bruce / Mission Amps]

I found some info that max is 16ma.

Put a 470 ohm 1 watt resistor on the screen grids of the 6V6 sockets (look at the layouts of black face and silver face 6L6GC amps) and then run those JJs at around 26ma-28ma with that amp. Since you are doing the math, after that remeasure your plate voltage and it will be lower too.

[7xa12]

I have the 470 0hm resistors there (2 watt) between pins 4 and 6
my first BIAS readings was very low 5.7 mA, so I set to 16mA. voltage plates did not change significantly after that.
so I tried to set around 21Ma but some oscilation sound from the speaker occured so I freaked out and left it at 16 mA.

[7xa12]

I am confused with those 26-28 mA Coud ypu explain why so high? Ido not want to fry the tubes

Thanks again Bruce.

[g1]

The higher numbers Bruce gave are specifically for the JJ brand 6V6. I would bet he has found them to sound best biased to that number in this model of amp.
The JJ 6V6 is rumoured to be something between a 6V6 and a 6L6 so it can be run hotter than a regular 6V6. They are also rated to be able to withstand higher plate voltages.

[Bruce / Mission Amps]

I have the 470 0hm resistors there (2 watt) between pins 4 and 6
my first BIAS readings was very low 5.7 mA, so I set to 16mA. voltage plates did not change significantly after that.
so I tried to set around 21Ma but some oscilation sound from the speaker occured so I freaked out and left it at 16 mA.
[ATTACH=CONFIG]25408[/ATTACH][ATTACH=CONFIG]25408[/ATTACH][ATTACH=CONFIG]25408[/ATTACH]

OK, then I think you have something else pretty wrong there... Those JJ6V6 tubes at 430vdc will be fine at 26ma-28ma and I'd fully expect with the B+ rail loaded down, the plate voltage will come down 15vdc - 25 vdc fairly easily.

Is this a real Fender amp or a homebrew clone of some kind?
With the standard +3Hy choke and those 470 ohm screen resistors, your screen voltage should not be higher then your plate voltage... something is amiss.

Just saw somewhere you saying it is a homebrew amp.
Show us a picture of your eyelet board and maybe the way your B+ rail is wired up....

[7xa12]

the Choke is beefier (4H@90mA DC) Hammond 194B. all TR are Hammonds PT- 291BEX OT- 1760H
I retested the resistors they are fine ( 467 Ohm) I chosed matched pair with resistance as close as possible.
I left the BIAS at 16mA. I measured the second tube (V8) it stays at 15 mA so it is abou 1mA difference.
I pluged my guitar and played about an hour. no red plating or smoke. Both channels works. reverb is very nice.
there is a litlle hiss on idle. but nothing serious - I am suprised with that because in my grounding the all 3 mF caps are grounded at buss wire ,preamp,PI . and the first one after the choke. the rest 22MF are with CT and cathodes. I can rearanged the grounding easy to check waht is the best in the amp.
I noticed that my wall voltage is unstable is flying between 230V - 245V. so I would prefer to stay on the safe side with BIAS.

[7xa12]

[7xa12]

[Bruce / Mission Amps]

If you suffer an oscillation by increasing the idle current from 16ma to 22ma-26ma... I'm sorry but I think you have something wrong there. It could be as easy as a single wire near the phase inverter acting up by capacitively coupling signal or coupling in the NFB loop or the reverb section... etc.
However, if you are happy with it as is... I can't complain.

[7xa12]

Bruce thanks for your valuable comments, I left the multimeter off, and tried to find what BIAS settings I like the most in the amp. ( testing with ears)
next checked the BIAS... it turned out that my favorite settings are around 18-22Ma. I find it warm/ nice and clean and lovely for Jazz I play.
no oscilation this time but I did not go higher It might be that I overreacted on the other hand, but it could be a problem. time will tell.
It is new build from a scratch and I will be retesting it and playing it with guitar as long as I can. I have an old worn orginal Fender speaker I got for free, I just used for testing ( I am planning to try to use different one) and mayby building a cab. I admire all you people who did not have an internet source and you were sucesfull as amp builders. it is quite easier today.