Hi everyone, many thanks for the tips and pointers, especially the one from Dave. I checked the switch contact, 1D is the only extra switch being used on all ranges from 0.5V upto and including 20V per div and this checked out just fine.?
Further investigation on the input for Channel A showed that R3 should be 990k but was reading 11M so there was the culprit. Problem being this resistor sits in what appears to be a metal shield which soldered to the ground plane and is also shown on the component map as MP1? This resistor sits across a isolation slot so I'm guessing that is meant to be providing extra protection against stuffing over voltage into the channel via the probe and the shield is contain any flash, is that right?
Anyway, purely as a test I have soldered a 1M resistor across it and tested it and it works fine so I'll need to replace it with the correct rating and stuff it back into the shield?
The other issue I have is that the delay timebase knob has broken up and left the brass boss on the shaft which I cannot get off as the grub screw just chews up the allen key head all the time. So does anyone know where I can get new knobs for the time base (both knobs) and both of the shafts as I see thats the best solution to the boss problem and there are missing grub screws so a set of knobs with them fitted seems the best option if possible.
