EL34 bias way too high

[fossilshark]

So I got this 2204 built with every connection double checked but no matter what I do the lowest the bias voltage (turning the bias pot) will drop down to is -73v and I'm pretty sure that's way too high.

Why does the bias pot look different than the rest of the pots in this schematic? I have the middle and another pin shorted together going to ground, is this correct?

Also idiocracy here, can I run this John's without the 47p cap on the phase inverter and 100k feedback resistor? Just curious (will be adding them in when they come in)

[sluckey]

So I got this 2204 built with every connection double checked but no matter what I do the lowest the bias voltage (turning the bias pot) will drop down to is -73v and I'm pretty sure that's way too high.

Maybe you used a different PT than Marshall used. You can drop this voltage by increasing the value of R30.

Why does the bias pot look different than the rest of the pots in this schematic? I have the middle and another pin shorted together going to ground, is this correct?

The bias pot physically looks different too, right? Marshall used a different schematic symbol for a trimmer pot.

Also idiocracy here, can I run this John's without the 47p cap on the phase inverter and 100k feedback resistor? Just curious (will be adding them in when they come in)

Sure

[shooter]

drop down to is -73v and I'm pretty sure that's way too high.

what's the full "range"?
my understanding the more neg(-) the bias volts, the lower the tube current.  Would guess - 73 would get the tubes close to cut-off?

[fossilshark]

I assumed I could just use a pot instead of a trimpot, am I wrong? I wasn't brave enough to keep turning when it went up to -85v, I think you're right about it being a different PT. Should I double R30? How much is too much resistance here

[sluckey]

Just do it. You need a range of about -30v to -50v. Don't put any tubes in until you get it right.

[shooter]

if you haven't read this yet comes in real handy

http://www.aikenamps.com/index.php/what-is-biasing

[fossilshark]

Aye slucky you killed me on the spot. Had all tubes in and it's probably been booted up for a total of 3 minutes now oops...

[2deaf]

You would have to have 600V_rms or more to the CT of the PT to get -73V at the bias point with the circuit you posted.  It seems more likely that you do not actually have the circuit right or you are not measuring it right. 

[fossilshark]

2deaf you would be correct. Still no sound out of the amp (not even noise) with the bias at -53v(no tubes/load) so it's time to triple check my output section. Out of curiosity should I have the common for output transformer connected to ground as well as the speaker jack grounds? And how about the center taps on the power transformer? I'm following the original schematic as close as possible.

[shooter]

if you ohm along the red line to chassis ground, should be close to 0

[tubeswell]

2deaf you would be correct. Still no sound out of the amp (not even noise) with the bias at -53v(no tubes/load) so it's time to triple check my output section. ...

Suspect the OT has been killed. (Common for amps running EL34s way beyond their design parameters). Disconnect the OT and do a Pr:Sec VAC test with a low powered AC source on one of the secondaries. (Make sure your VAC source can absorb a shorted load)