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Are the 5100 series scopes known for intensity/focus problems?

Dave Seiter
 

I ask because I have three 5110s I've decided to get working so I can whittle them from the collection, and after solving many other issues, all three have some combination of intensity/ focus related issues. I got them all from the same auction years ago, and all of them were missing the metal CRT connector cover. (I guess that should have been a hint!) On all three, removing and reseating the CRT connector solved at least one other problem. They are all the newer versions (square heatsinks on the H and V output xstrs, and row of fuses in the LVPS).

Sometimes, depending on settings, I get classic double peaking behavior, but sometimes it's more like a scratchy pot (same scope). In one case, the focus literally has two shapes- it remains stable until the knob is turned past a certain point, then it changes to it's other stable state. I'm thinking that one might be a bad pot. On some settings the focus and intensity interact a little, but not on others. The plugins all work just fine in the 5111.

Lastly, on one scope, each trace begins with a small spot, regardless of settings (except for x10 at higher speeds, where the spots vanish, but the retrace is visible. Must be a blanking issue, but that's the last problem I noticed and haven't looked into it yet.

-Dave