Metropoulos Forum

Hi, Just finished to assembly and bias (41) the kit (JTM45 head) and some challenges came up:

1) most of the voltages are high:

1 2 3 4 5 6 7 8 9
V1 211 1.7 3.4 3.4 213 1.7 3.4
V2 173 1.2 3.4 3.4 312 173 175 3.4
V3 361 5.1 3.4 3.4 360 5.1 3.4
V4 3.4 400 406 -44.5 407 3.42
V5 3.4 400 406 -44.5 407 3.42
V6 408 325 325 408
V1,2,3 are Mullard 12AX7
V4,5 are KT66
V6 is 5AR4

2) After connecting a 8 Ohms speaker to the output, the sound is distorted at very low volumes (using a PRS with low volume) at any of the 4 inputs and the presence doesnt work. I m not sure about treble and bass because the distortion is more noticeable.

3) included some pics of the assembly.

I would appreciatte if there is a error tracing tip or if somebody can share some wisdom about this.

Thanks
Adrian

It looks as though you've committed the classic error. At the third preamp tube (the phase inverter) there's two 1meg resistors with a 470 ohm thata's supposed to go between them -- and it looks as though you've put a 470K in its place. Yours is currently a yellow-violet-yellow color code; find a yellow-violet-brown to replace it, and you'll get the headroom and volume in the amp, as well as voltages that will drop in line better at that third preamp tube.

Well try right away. Thanks for the quick reply...
I m happy that at least is classical
thanks
Adrian

right on the money.
All tensions are ok (only tube V3 Pins 3 and 8 are now at 40V. Is it fine?) , headroom is there and tone controls work.
Thanks for the quick rescue.
Adrian

Hi, Soundwise everything is great. the only issue after a week of use is the presence pot that is scratchy. Is there anything to reduce the hhhhhhhhhhhh sound when it pot is turned??
Regards
Adrian

The cure for the scratchy presence pot is to switch to a 25K pot, with a 4.7K resistor across it. Fender did this in the early sixties, it took Marshall another 15 years to figure it out.
It's DC across the pot and it's normal when you're using the 5K pot. Most people don't worry about it, unless you change the presence setting a lot at gigs or something.

I just made a note of that.
Thanks Flames