7104: Self-blurring focus

Bruce Lane

Well... I think I may have a couple of leaky caps or something.

Having cycled the pots a whole bunch on my newly-acquired 7104, I find that they're doing well enough. However, it looks like there may be an issue in the focus section.

What will happen is that the trace will be razor-sharp and hair-fine one moment, and then it'll start blurring. This affects the entire screen (readout included). The interesting thing is that the focus will blur up to its (apparent) maximum degree of 'defocused,' and then it'll snap back to razor-sharp and clear. It'll do this three or four times, and then stay sharp or blurred at any given moment. After the 'scope's been on for an hour or so, this behavior disappears.

Has anyone seen this symptom before? I suspect thermal-intermittent caps in the high-voltage area, but I don't yet have a service manual for the unit. Pointers appreciated.

Thanks much.

Bruce Lane, Owner & Head Hardware Heavy,
Blue Feather Technologies -- http://www.bluefeathertech.com
kyrrin (at) bluefeathertech do/t c=o=m
"If Salvador Dali had owned a computer, would it have been equipped with surreal ports?"

Join TekScopes@groups.io to automatically receive all group messages.