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So one of my NOS Tesla EL84 died a horrible death not long ago and I fear it might have done some additional damage to my 18W Plexi. voltages all seem normal except for the PI (V3). Output volume is very low on both channels, I've tried swapping tubes around to no avail! Can anyone help me, point me in the right direction to figure out where the problem is?

Here are the voltages I measured with the specified values in ():

V1:
pin 1 (155VDC): 143.0
pin 3 (1.0VDC): 1.00
pin 6 (155VDC): 145.0
pin 8 (1.0VDC): 1.02

V2:
pin 1 (180VDC): 178.6
pin 3 (1.5VDC): 1.67
pin 6 (272VDC): 262.5
pin 8 (180VDC): 178.7

V3:
pin 1 (220VDC): 178.6
pin 2 (52VDC): 32.4
pin 3 (75VDC): 62.3
pin 6 (217VDC): 272
pin 7 (62VDC): 58.7
pin 8 (75VDC): 86.5

V4:
pin 3 (12VDC): 11.3
pin 7 (345VDC): 333
pin 9 (340VDC): 322

V5:
pin 3 (12VDC): 11.3
pin 7 (345VDC): 330
pin 9 (340VDC): 322

V6:
pin 1 (290VAC): 300
pin 3 (350VDC): 345
pin 7 (290VAC): 300

Figured it out!! it was only a blown cap in the phase inverter section

Good Job. How did you figure it out.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

The voltages on pins 1 and 6 of the PI being out of spec were obviously the problem (or at least a good indication of where to look for the problem). I checked the resistor values from the PI section with my DMM and found none that seemed faulty. I read through the Geofex tube amp debug PDF (in the ressources forum) and figured I'd start replacing the coupling caps going to the power tubes. First one I replaced didn't help but as soon as I replaced the second cap, voltages to pins 1 & 6 both came back to 210ish volts and the amp was alive again!!

I'll keep a close eye (ear) on it to make sure nothing else was damaged!