TR JM Signature Build

[fred.violleau]

Hey guys,

It's been a while, and I have been busy building a TR JM Signature.
- 3 way bright switch
- LNFB on a switch
- 3 way gain structure
- contour bypass
- HT fuses

Again, took my time to try and source some period correct part, and recycled an old Fender PA100 for PT, OT choke and reverb parts.
Got a used chassis from a member of this forum as well as the board that look like Taylor's work.
Unfortunately the chassis was damaged and bent when I received it (dunno if it was before shipping, or if was damaged during shipping...)
Did my best to set it as straigth as I could and then proceeded with the build.

Used RG59 for the long runs and RG188 for the short ones.
Tried to salvage some caps from my very first build.
6PS Orange drop pretty much everywhere and draloric when I could find the right value.

PXL_20221023_140721447.jpg

Power up unloaded gives me the following values :

On stand by :
mains : 120 VAC
HT rectifier : 475.3V VDC
bias : -40.2V

In operation mode :
HT rectifier : 413 VDC
B+1 OT : 413 VDC
B+2 PI : 409 VDC
B+3 : 372 VDC
B+4 : 368 VDC

-97V before the 220k bias resistors

dropping resistors as follow : 2.2K > 22K > 2.2K and 10K for reverb

I tried to play the amp with an old set of tubes (and unmatched quad).
I got sound and the preamp seems to work as well as reverb
Overall volume was very week and I had a big HT voltage drop as soon as I flip the standby switch. Main HT would fall around 215V.

Nothing would smell funky, but the amp hums and volume is very low.
I need to get a fresh set of tubes to make sure that there is no trouble here.
Checked all the ground points continuity where needed, everything seems fine.

Will report as soon as I get a fresh set of tubes somewhere next week.

'Till then, a big shout out to this great community that made this build possible : Aaron, Taylor, Ryan Colgan, Marcus, Martin Manning, Ian, Dimitris, Talbany and the all other builders who paved the way for us.

Cheers!

Fred.

[ijedouglas]

Very nice! Congrats!

[rccolgan]

Wonderful!! I bet you'll find the gremlins in your build and you'll be playing in no time. Great work on the build!!

[Guy77]

Looks great! Congrats.

Guy

[fred.violleau]

Thanks guys for the kind words.

I went to the local music store to buy some tubes and they are out of stock, nothing left, it is crazy.

I need to order some online.

Tried again the preamp through another build and everything works fine although the switch for the contour knob seems to have no effect. It does not make any difference if contour is engaged or not, so I may have to revisit this...

Everything else in the preamp checks out.

Do you have an idea as to why the B+ would go down that much when I flip the standby switch?

My issue the a obviously in the power amp but I have not found out yet what it is. Will review the schematic to make sure that I did not do any mistake here.

Fred.