Difference in power tube plate dissipation - Express

[Miket]

Hey guys, I'm just going through the voltage testing, tube tasting and biasing stage in my newly build express.
Everything sees to be on the right track for the most part. But my question today is regarding difference in plate dissipation of power tubes at idle.

Concerning a pair of apparently matched RFT EL34s from eBay. This is the fist time I have used them in an amp. When biasing them using the 1ohm resistor method, I'm noticing a difference of 14mA between the two tubes.

Now I know it's not uncommon and sometimes desired to use unmatched tubes in the output section of an amp. But are these two tubes too far apart? One being biased hot, the other being biased quite cold.

At the moment I'm running v4 @ 400 plate volts - 47mV drop across the resistor.
And v5 @ 400 - 33mV.

Interestingly, I left my probes on the resistor and examined what happened when playing an open e chord with all dials at 12 o clock.

V4 went from 47mV up to 160mV, while v5 in the same scenario went from its idle of 33mV up to 68mV.

Could there be something wrong with the tube in v5?
Is this difference in idle current enough to be detrimental to the sound and performance?
It doesn't sound bad, it definitely has trainwreck characteristics. However I haven't been able to open it up completely yet, so I have only been playing through my attenuator. And have yet to experience it in all its glory.

This problem is exclusive to these tubes, other tubes biased ok. And the same thing happens if the tubes are swapped from one socket to the other.

Look forward to your responses guys.
Thanks in advance.

Regards, Mike

[martin manning]

To be clear, are you saying the low current reading follows the tube or stays with the socket?

[Miket]

Follows the tube

[martin manning]

That says that tube has gone bad, no?

[Miket]

I did some tube swapping today and it seems that the tube at fault was the one drawing the most current. I'll have to get it tested.