Express bias problem

[bcat01]

I am new to posting here, but I have been reading for a while, and I appreciate all the great info here.
I just built an express, but I can't bias it. It red plates, and when I get a MV reading across the 1 ohm resistor, it says .1, if I switch to 2V, it says .274.
I have strummed the guitar, and I hear the potential, so this is killing me.
I have tried 6V6's and EL-34's.
Any suggestions?

[martin manning]

Pull the power tubes out and measure the range of bias voltage you can get by turning the trimmer stop-to-stop. You need something like -30 to -50VDC.

Measure your supply voltages too, and report back.

[bcat01]

range is -23 to -33. The voltages are pin: 3/412 4/407 6/407. Should 4&6 be the same?

[martin manning]

4 and 6 are the same because there is no current flowing through the screen resistor. You may need more than -33V to bias correctly. Is your R29 (the resistor connecting the bias supply circuit to the PT) 220k? If so you may need to lower it. I used 150k.

[bcat01]

It is 220k, I will switch it out & post results. Thanks...

[bcat01]

I found a 120k - got me -40 to -50. Red plated, this time the fuse went. Once again the meter wouldn't read in the 200MV range.

[martin manning]

Hmm... -50V ought to be enough to shut them down completely. Is it possible that you have some DC leaking through the PI coupling caps? Measure the DC voltage at pin 5's with the power tubes out. Re your inability to read mA, are you sure your meter is working? Batteries good?

[bcat01]

Thanks for your help. It was a mistake due to my "color confusion", I missed a wire that was close to the same color as the board - at least to my eyes, and my smaller print out. When I enlarged the .pdf I could see it. Going from the bias on the board to r16 & 17.
It sounds great, but it will need some tweaking for noise.

[martin manning]

Floating grids- no wonder you had redplating! I guess your meter only reads to 100mV on the mV scale, and the 0.274 on the 2V scale was correct. On the noise try different tubes in V1, and I found along with using a bottom cover on the chassis, a shield on V1 helps some too.

[bcat01]

I haven't tried any of my "good" tubes yet. It still sounds good - at low volume so far, I will open it up with the band today and put it through it's paces. I did chopstick around and I think I might eventually move the cap on the presence pot.
I can hear the transformer hum when I turn the amp on, before I hit the standby switch. Not so with my other amps (or I haven't noticed), which could be a contributing factor. I think I will learn a lot when I turn it up though.