Metropoulos Forum

Hi all, I am having a problem getting any sounds out of my 2 year old Metro SLP, 100 watt. I recently blew a Mains fuse, and when I replaced it I noticed that I had a tube replating- heard a crackle before I shut it down (no burning smell though). After replacing the tube, and putting in another new fuse, I get no sound at all- not even the expected hum. It powers up fine, and my voltages look good across the board, but nothing at all coming out:

V1 163 0 1.1 3.35 3.35 213 0 1.8 3.35
V2 166 0 1.1 3.35 3.35 303 166 168 3.35
V3 235 22 40 3.35 3.35 228 24.5 40 3.35
V4 GND 3.35 494 492 -46.5 494 3.35 GND
V5 GND 3.35 494 492 -46.5 494 3.35 GND
V6 GND 3.35 494 492 -46.5 494 3.35 GND
V7 GND 3.35 494 492 -46.5 494 3.35 GND

However, I am getting some really strange readings when I measure my current at V5 & V6 (no V4 or V7). With the original Mullard EL34's that shipped with the amp, one tube pulls about 20 ma while the other was around 50. I swapped out the 2 other Mullards with the one that was drawing too much and they were even higher. When I changed sockets, the readings followed. I replaced the Mullards with Tung Sol EL 34b's, and those were 17 and 19 ma, and I could max them out around 27 with bias adjustment. I am worried about the current readings being all over the board, and obviously thinking I might have a bad OT.

I will try to get a good picture of the insides later, but wanted to get this out there and see if I am missing anything obvious.

Thanks for your help!

At a first glance it is not looking good for your OT.

What you have done so far is exactly correct.

Next step would be to run through the amp (maybe try some known good preamp tunes (optimism rather than expectation that it will work ) with a sine wave input (or someone thrashing away on a guitar) with a probe to see if you are getting signal through the path it follows to the OT.

I would sub in a spare OT but I suspect you do not have that luxury?

Thanks for the reply! Unfortunately no, I dont have a spare OT that I can sub in, but I will definitely run a signal trace later this week, and I do have some known good preamp tubes that I can swap in.

One thing I forgot to mention is that I did get a slight sound out of the speaker when I was checking the plate voltages on the output tubes. Not sure if that makes a difference or not.