mesa triple rectifier

[JC@]

Hello, would someone let me have a look to the bias supply part schem for the triple rectifier?
Thank you.

[defaced]

I don't have the schem in front of me right now, but I'm pretty sure you can get it from schematicheaven.com, and the bias supply is on the same page as the power supply.

[JC@]

I just went there, but the triple is one of the few missing schems...

[defaced]

The bias supply should be the same as the dual - the only real difference between the two is the addition of two power tubes and requisite changes in the trannys to accommodate that. I've got the schem at home, I will verify that the bias supply is the same when I get home.

[JC@]

The bias supply should be the same as the dual - the only real difference between the two is the addition of two power tubes and requisite changes in the trannys to accommodate that. I've got the schem at home, I will verify that the bias supply is the same when I get home.

Please do Mike.
I see there are two resistors connected in parallel just before the point where the 220K resistors join together. On the Dual schem one of these resistors is a 22K and the other is a 15K one, and this 15K one is connected on and off in parallel via the bias change switch, not hardwired together like in the Triple...

[defaced]

I'm thinking that switch is the "6L6/EL34" switch, so your Triple should have that.

[defaced]

Well, it appears that the schems Mesa sent me when I was doing the bias mod to my Triple were in fact schems for the Dual. What are you trying to do exactly, and what generation of Dual do you have 2 or 3 channel?

[JC@]

Well, it appears that the schems Mesa sent me when I was doing the bias mod to my Triple were in fact schems for the Dual. What are you trying to do exactly, and what generation of Dual do you have 2 or 3 channel?

I don't know really what model it is. It's a three channel one.

I'm fitting an adjustable bias circuit, and I went the hard way pulling out the board. Those two resistors in parallel I mentioned are in fact a safety way to obtain some bias in case one of them fails open.

I'm almost done now. With 20K there I still get a cold 27mA per tube, so I have to change to a lower resistor value in the resistor pot tandem.

I get just 370 Vdc on the plates, is this normal?

[defaced]

My 3ch Triple rec ran in the mid 400s.

This may be of assistance, my post on a different board asking for help modding my Triple Rec. http://mesaboogieampforum77319.yuku....wtopic/id/2148

[JC@]

It's ok now. The B+ was low because the amp had the "power" spongy/bold switch set to spongy. I get a bit more than +420 Vdc on the plates and that's better.

Thank you for your help. I believe it is now done.