Metropoulos Forum

just ordered parts for a new build

CM laydown PT
Drake 2" - 132 2.2k OT - 0100JM-VZ from MM
3.8H choke - MM
chassis & plates - George
Guts - Valvestorm
A few Iskras
Case - Mojo

Standard DF recipe

Pics to follow

Nice! I'll be ordering the same CM PT also, already have a Marstran 2" 2.5k output and mustards, using the D.F. specs of course. Can't wait to get started...

Kevin ~ can't wait to see and hear how this unfolds

Build's progressing. amazing how the time flies with little evidence of work completed...

a few points for future reference:

measure dc resistance between both heater circuits after installed to help check for poor solder joints. both of mine measured .5 ohms.

double check the impedence of the OT primaries (red, brown, and white wires). my MM -132 OT had a diagram that showed white being the center tap. I installed it that way and measured red to tap and brown to tap and one was roughly twice the resistance of the other. lesson here - double check wiring diagrams whenever possible and dont just go off of other builds. wish colors were consistent but that appears to be a tall order.

I'm opting for the 4 5k6 grids and found a lot of NOS IRC 5k6 1w resistors, due to arrive in a couple days. other than that, power tube sockets are complete, output jacks, OT and filter boards are all complete. ~12 hours in so far, including doublechecking these sorts of things, drilling out the plexi panels and chassis for the different trannies and larry grounding.

Nice looking! Can you run the green wire like that to the impedance switch or is the switch upside down? I've always wondered if those other tap-ends mirrored the ones opposite.

double checked that and nope, top posts dont work. good catch.

Starting with 8ohm, 100k NFB on this one to start, along with 465v tap. We'll see how it sounds. Shooting for WACF tone on this rig.

PT is largely complete, along with switches, indicator, and fuse holders.

I was thinking you flipped the selector upside down.

How are you checking the impedence of the OT? I have a 50 watt 2204 build going that has me going in circles. The tube voltages check out, but all get is a "rrrrrrrrrrr" coming out of the speaker.

Since both hands will be inside the amp make damn sure to discharge the board, then measure DC resistance between the white, brown, and red primaries of the OT. Measure from CT, which is probaby either white or brown on the board to each of the brown and red legs on the power tubes (pin3). if the two readings are similar, its wired correctly. if one is roughly double the other, you've got the center tap and one of the primary legs mixed up (most likely white and brown). Mine measured about 22 ohms from CT to one leg and 47 from one leg to the other. Hope that helps.

YMI5150? wrote:Since both hands will be inside the amp make damn sure to discharge the board, then measure DC resistance between the white, brown, and red primaries of the OT. Measure from CT, which is probaby either white or brown on the board to each of the brown and red legs on the power tubes (pin3). if the two readings are similar, its wired correctly. if one is roughly double the other, you've got the center tap and one of the primary legs mixed up (most likely white and brown). Mine measured about 22 ohms from CT to one leg and 47 from one leg to the other. Hope that helps.

Yeah, it does. Mine is a Classic Tone tranny. White, Red, Blue. Apparently it must be copy infingement to color wire the same I guess.
The diagram seems to indicate the Blue as common with a small dot beside it. What measurements should you get on the secondaries?

tell me about it. take a look at this diagram sent with my OT. first, its labeled incorrectly. I didnt' order a 50JM but assumed it was the same for both trannies. second, if you read that, I think most would interpret the brown as the center tap on the primaries. if i hadnt measured, it would be wired incorrectly... I'm not sure if the secondaries can be measured the same way or not. Guys?

So on that its the Brown CT? Apparently mine has them at the top of the diagram, but I'm not sure now. Guess I'll have to measure to make sure.

...............

edited to keep the thread efficient

the saga continues. I emailed MM and they just replied appologizing for the wrong diagram. attached is the correct diagram for the 0100-JM-VZ tranny with the 2.2k primary. It appears that the center wire is the CT so Shannon, that should help. The issue now is all my secondaries need to be rearranged...

just got back from lunch. the NOS 1W 5k6s were in the mail box so they were added real quick. they look very cool. opting to go that route rather than the period-correct 1k5s.

Had ensomnia this morning and started wiring the preamp board, complete with pink wire mojo. pics coming.

Getting close!