On the recently completed 485 I mentioned that I was unable to adjust out some peaking on fast rise time pulses. Decided to see if I could determine why. The pulses were fine until the last IC before the vertical output and that's where the issue was. Closer examination of that area revealed some prior gorilla has been in here. The IC was clearly changed out. And I suspect some damage to traces might have occurred which has screwed up impedance matching. So....investigated how difficult would it be to swap over the vertical board from the parts mule.
Here's that peaking.
First off...the service manual gives absolutely no instructions on how to remove the vertical board. So I was on my own. Turns out it's not too bad. Most of the board is modular except for 2 solder connections for the delay line. But the biggest issue was the vertical output IC is stud mounted to the chassis crammed next to the CRT.
Here's that stud on the right. Right in between the very delicate wires to the CRT vertical deflection plates. I was able to get a ¼ inch wrench (spanner) in there and VERY carefully remove the nut. Once that was done the board lifted and guided the deflection plate wires through the holes.
Here's where the board resided in the scope.
And here's the vertical board itself. The vertical output IC is the large round silver can on the right.
And the underside of the board showing the stud mount and the deflection plate wires. The mount did have some heat sink grease on it. Guess what I'm out of and need to order? Yep, some heat sink grease. When I get it I'll swap this board in and see what happens.