Boards are out, immediate issues are both triggering bulbs are rattling about in their hoods, the leads are broken off, as is the power on bulb. Can anything easily obtainable be substituted?
The main issue is the rather complex drum switch, the grey plastic thing like one of those musical instruments with pegs on a brass drum that plucks at different length strips on a sounding board, i forget what they are called. Anyway, I always thought it worked oddly, as pulling the knob just resulted in a squeaky raspy noise when turned. It's the drum in ModemHead's photo in this thread that does NOT have the cleaning paper under the contacts that I am speaking of. Not having used on of these scopes before I assumed it was turning a dry potentiometer. I have disassembled the drums and I assume the knurled bit of the shaft that enters the rear drum is supposed to be moulded or bonded into the back drum itself, so it can turn it? Well, it just pushes out from the front, revealing the knurled bit of shaft, and some plastic dust followed it. I assume the knurling is to give it surface area and texture to grip when it's moulded or glued into the rear drum I reckon I have some suitable aircraft adhesive that will bond it back in again, so the shaft can turn the rear drum. As long as I have had the scope it's not turned the rear drum, it's been stationary. I am sure that depending where it stopped it may have caused strange effects? The push button switches all have low resistance when closed and infinity when open, so assuming they are still low resistance with a load across them I can give those a clean bill of health. Is there a better yet safe way to test the contacts with the switches still on the board?
The toggle switches look a nightmare as they are plastic welded onto the boards and the contacts themselves are not accessible. I need to sit down when I am not tired and have the circuit diagrams in front of me so i van pin out the contacts on the board tracks. I suspect these ARE less than 100% the copper coated spring strips are manky, they just don't look good at all. I will have to get some of the de oxidising cleaner that's been mentioned.
If I can re bond the shaft in the drum, and get the damned thing back together as it's meant to be there's still hope. My worry is phasing a little cam that sits between the two drums and operates against a spring loaded peg. It was loose, so I have no means of knowing where radially it should be locked up on the shaft. It allows continual rotation in one direction, but due to the shape of the camit locks the shaft when it is counter rotated. It's WHERE it should lock the shaft that may be an issue
It's miracle these things work at all, I had no idea there would be so much electro-mechanical stuff to go wrong. I am thinking there's a lot to be said for my USB scope right now