Djstatix

Tolex job.

New caps

Maybe, I have no idea.  It has 6l6’s installed.  I replaced it with the factory 91k resistor.  Thought about putting a variable 100k potentiometer there but for now the 91k.  This amp had several owners I believe before me.  I’ve done the few easy gain mods too.  Re doing all the tolex for the amp and I’ve found a carvin cab to refinish as well.  I’ll post the pics when I’m done.

17 hours ago, MiKro said:

I had a long discussion about that very thing with Rob R as you said many put it at R127 and I was not positive. Rob R thought I was on the right track as well. LOL

mk

Your board looks like a 4C mine is a 4B.  Comparing to schematics.

any idea why r127 has two resistors in series?  C2 has a leg lift with a resistor in series too.

10 hours ago, MiKro said:

It is a trimpot that I had. Yes the insertion point was where R126 would be. On the schematic for the 1986 version may be different? Also not sure what tubes you use? if 6l6 then my values may not work as I was using EL 34 as my power tubes. It is a Round Trimming Potentiometer 1/2watt most likely I got it from Jameco or digikey.

One more thing the Bias value shown on most of the schematics is wrong. Since this is a fixed biasing scheme on the cathode side, you are doing all 4 tubes at once not each individual tube. like many amps. Also most Carvin amps were biased towards the cold side .

mk

Awesome!  Thanks for the help.  I have the 6L6’s installed.  I’ve seen where people installed the Pot on R127 but R126 makes more sense looking at schematic.

4 minutes ago, MiKro said:

They are posted in the first page of this thread. Very easy to make. Post number 4 in the thread.

mk

I can see the board and resistor.  That potentiometer, where did you get it?  Looks like r126 is the insertion point.

I’m interested in the bias board you made.  Any help with parts used and pics would be nice.