Home Brew JCM-800 Bias Problem

[Just Mike]

I built a JCM-800 2204 from a Ceriatone layout and my bias voltage reading is way low. I'm trying with a new set of Mesa STR 447 EL34's. (Ive heard these are the same tubes as EH's) The layout calls for a 220k Bias range resistor and a 56k in series with the 50k pot. I started by changing the 56k to a 47k...minimal difference. I started upping the range resistor a little at a time and saw very little difference. I'm finally at 450k range resistor and still can't get above 9mv across the 1 ohm resistor. I know this has something to do with the Mesa tubes because others I've tried get closer, but are still low and 3 other sets are wildly mismatched. That's why I'm trying the Mesa's. Plate voltage (pin 4) is 490. Does anyone know what's going on here? Many thanks.

[stef]

Plate voltage (pin 4) is 490. Does anyone know what's going on here? Many thanks.

Pin 3

[woold]

What negative voltage are you getting on the non-earthy end of the bias pot?
What -ve voltage is on the EL34 grids? (pin 5)
What is the range of the -ve bias voltage when you adjust the pot.

What is the EL34 plate voltage which is, as previously mentioned, pin 3

If you post a picture and I would be happy to double check the wiring around this area.

[Just Mike]

Just thought I'd let y'all know that I found the problem. I built the amp using Classic Tone transformers and I incorrectly assumed that the CT wire for the heater secondary was the black wire....Well, it's not. It's either brown or orange, I don't have it in front of me. So I actually had one of the 6.3 VAC sides grounded and I was only getting 3vAC to my heaters.
FYI, the amp will (kind of) work but the output will be very low and even though all of the DC voltages are correct, the bias voltage will never be in range. I guess this will only happen on a new build that's wired wrong, but it's something to look for in a new build I guess.
BUT, it's fixed and it rocks!

[Haze13]

I bought Transformers from TubeDepot (Classic Tone and Mojo), and for every transformer there was a documentation. Don't you have same documentations? There is an explanation about every wire and their colors.