Just when I thought I was getting closer. There was a spark sound and smoke from the left side of the output board !! I was nowhere close to that board. Was checking the FM section of Electronic Switch board (PC11). Dismantled all the output transistors all over again and checked them. Sure enough both the output transistors were blown + Emitter resistor (R21) + output driver TR2. I have to order the .12ohm resistor. So will need to wait another week to start again.

Dahiyas

Yes I resolved my problem, very simply due to sitting unused for a period of time the grease on the worm gear of the motor which drives the solenoid operated clutch for each of the VOL/BASS/TREBLE/L/R potentiometers had gone very stiff, I used silicone grease which was probably not a good choice....operated by hand a couple of times and its now running free.

Regarding your post above....during one of my restorations Henrik (site member), I think it was Henrik AKA Square Four, advised that the PC11 board will over time bow significantly in its mountings and has been known to do so to the extent that the solder side can contact the chassis and cause a short. Looking at this board on mine....its very long and narrow, i could actually see a bow. Not had a problem myself but as a precaution I installed a strip of thin mylar strip the same size as the board between the solder side and the chassis......

Just  a thought ;¬)

Closed this up today and powered up in the workshop......considering its 50yrs on the planet, and some not inconsiderable restoration....some members may remember its condition when it came into my possession for a £60 outlay.....it still sounds extraordinarily good.  

Awesome Craig !!

I have been travelling quite a bit and haven't been able to get to the system again.

The board is bent slightly but not enough to touch anything. In addition I had added insulation earlier.

Hopefully will get time towards end of the month.