JMP50 Clone Build, Part 7
A long night’s work on the JMP50, soldering the leads onto the turret board before installing it in the chassis.
I wanted to push on tonight and mount the leads on the turret board and get it installed in the chassis. I thought this would be quick and easy. And while it wasn’t difficult, it did take a lot longer than I expected, mostly because I was going back and forth between Ceriatone layout pictures and Metropolis’ excellent 50 watt build guide. I was trying to adapt Metro’s colors to the Ceriatone layout and double-checked my work frequently. I figured that it would be easier to do it right now rather than having to pull the board out of the chassis after it was all together.
This gives a pretty good idea of the wiring. The power supply end of the board is as the top right of the picture. Both pairs of twisted yellow wires will connect to the chassis-mounted cap can, the one in the middle of the board goes to the cap can mounted next to the choke. You should also be able to make out a yellow/green wire at the power supply end; this goes to the cap can that feeds the power supply. The twisted red leads go to the HT taps on the power transformer. Black/red leads are jumpers that connect various turrets.
And here’s what it looks like from the top. Not as much to see. The twisted orange/green pair will to V4 and V5, pin 5. These are usually routed beneath the board, but I put them up to so I can remove them easily when I install a Lar/Mar PPIMV.
I used 8-32 standoffs from Mouser to secure the board. Even though there are no clearance problems, 8-32 was probably too big and I should have used 6-32 instead. And, oh fuck, one of the standoffs broke while I was tightening up the lock nut.
The leads to the HT taps on the power transformer and cap cans are connected.
You get the idea.
Here the here the flying leads are connected to the PEC pots. Notice also the ground wires connected to a buss bar a the back of the turret board. This idea came from Ceriatone and was necessary because you can’t solder buss bar to the stainless backs of the PEC pots so another grounding scheme had to be used.
Why did I take another picture of the power transformer? Because I was tired?
I was verytired at this point. This was after Midnight, and I had worked on the amp for three or four hours. My judgment must have been impaired by this point because instead of stopping for the night, I went on and started mounting components in the turret board. No pictures, though. (Note to self: stop working on amps when you’re so tired you can’t read resistor codes.)