Metropoulos Forum

a buddy of mine asked me to take a look at his old Carr Mercury because it wasnt passing any signal at all. i spent a little time looking through it. all the plate voltages and bias voltages are right where they should be. when i rock the amp or even hit the reverb tank there is still no audible signal that passes. Im thinking the problem may be somewhere within the first two gain stages right before any of the reverb stages. does anyone have any insight?

since you have sound and think its the first to stages start with the input jack and work your way through.
voltage on the first two tubes?

Do you have access to a signal generator, can you download one to a computer? or even a metronome or tuner that has a continuous A440 reference pitch?

Can you hear any hum from the speakers at all?

i can get hold of a metronome with a constant 440.

there is no audile hum from the speakers at all.

the voltages are
V1-240
V2-420 (reverb driver)
V3-240

the bias for each preamp tube seems to be on point, around 1.8v with the exception of the reverb driver which is around 5v

EL34
plate-475
screen-460
bias- -32- -45

i neglected to check the grids of the preamp tubes for any DC leakage. this can be determined if there is any voltage at all on the grids, is that correct?

noworrybeefcurry wrote:i can get hold of a metronome with a constant 440.

there is no audile hum from the speakers at all.

the voltages are
V1-240
V2-420 (reverb driver)
V3-240

the bias for each preamp tube seems to be on point, around 1.8v with the exception of the reverb driver which is around 5v

EL34
plate-475
screen-460
bias- -32- -45

i neglected to check the grids of the preamp tubes for any DC leakage. this can be determined if there is any voltage at all on the grids, is that correct?

Hopefully it's not the OT

Anyway what I want you to do is plug the metronome in to the input (most have an 1/8th jack). if yours doesn't have a jack, just download a free signal generator on your computer.

put the constant sine frequency into the input, and put the controls at noon. Take your DMM set to volts AC, follow the signal path by measuring the AC output on the output side of the coupling caps. If you all of a sudden have no AC, you have found a dead spot, and where to concentrate.

thanks, ill be sure to do that. i wont have access to the amp until next week some time, but ill keep you updated.

just curious though, how would i go about checking to see if it is the OT.

noworrybeefcurry wrote:thanks, ill be sure to do that. i wont have access to the amp until next week some time, but ill keep you updated.

just curious though, how would i go about checking to see if it is the OT.

easy connect Bench OT, it is the best easiest most reliable way to test.

joey wrote:

noworrybeefcurry wrote:thanks, ill be sure to do that. i wont have access to the amp until next week some time, but ill keep you updated.

just curious though, how would i go about checking to see if it is the OT.

easy connect Bench OT, it is the best easiest most reliable way to test.

Whats bench OT?

Its just a spare ot I have on my bench with quick connect lugs so I can test

the Carr is a SE EL34, i only have a spare PP OT. I should be able to ground one side of the OT primary for use as a SE OT, is that correct?