Wow that's a looooot of CRT's in there !

I guess when it's the CRT era, you do everything you can think of with CRT's.....
I started work on the intensity balance issue.
Tek was nice, it's all very tidy and organised in there, and the intensity control circuitry has its own dedicated area, its own set of ceramic strips.
Only Problem is that it's partially obfuscated by the big handle bar...
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So I removed it. Excellent access now !
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It was not that hard... I should have done it when I washed the scope, would have made my life a tad easier and I would have been able to clean that area easily. Never too late though, so I proceeded to do just that... clean the tiny bit of grime that escaped the wash.
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Of course I was as frugal as possible... I simply sprayed one squirt of cleaner directly into the bristles of a soft brush, then lightly wiped the grime off the ceramic strips and components. Then wiped the excess with a kitchen towel.
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Then I started investigating the issue.
I noticed there was a bare wire that was running underneath the trimmer uh.... I lifted the trimmer to have a better look, and confirmed the "issue"... much more of an issue when you see that the trimmer has a huge, long screw sticking out of it, very much likely to be touching that wire !
So I pushed the wire as far down as I could, so that it clears that screw.
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Then I measured the value of the trimmer, because there are two manuals for the scope, and early ones are supposed to have a 1M trimmer and the later ones like mine, a 3.5M one.
Mine measured at.... 400K !

I don't know it's that's intended or not, could not find markings on the trimmer that looked like a resistance value.
I can't be 100% sure whether it's normal or not, because I noticed this scope does NOT stick to the manual !
They modified the circuitry like this I think.. I tried to make a drawing of it :
As a reminder, here is again the official schematic :
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So basically instead of having each beam be controlled by each end of the trimmer, what they did is wire the trimmer with only 2 pins, as a simple variable resistor, and it controls only one of the two beams. For the other beam, they replaced the trimmer with a fixed resistor of 1.8M, which is about half of the 3.5M value that this trimmer is supposed to have... hint hint... so maybe that trimmer measuring at 400K is not normal. I don't know.
Then I powered up the scope to see if lifting that trimmer away from that wire underneath it, would make any difference at all.
It certainly did : I got sizzling noise and a few pops and tiny flashes... then the CRT losing life. Pulled the plug... maybe the kitchen towel did not dry the couple drops of cleaner well enough then...

So I tried to be more thorough this time. I shoved a micro fibre towel through the components, to reach the surface of the deck, helped with a screw driver.
Then blew some hot air using the hot air rework station.
Then powered up the scope again. Zero life on the CRT.... I killed that scope again !

Told you, I should not be allowed to work on these scopes.... still, I want to believe that overall he is still better off in my company.. the alternative would have been the junk yard. At least with me he got a good clean, lots of diagnosis and repairs, and a nice warm dry place to live in.
So I might not be perfect, but I am still much better than the other option... No, not trying to justify my mistakes, just trying to feel less bad about them

OK so I hope I can fix it and make it go again....
