I have been using my Tek 465 for decades, and am still quite satisfied with it. But nevertheless, I bought a cheap broken unit on Ebay. It had the description "verticle switches defect", so I was expecting to fine the plastic joints between the vernier rods and the potentiometers to be broken due to old age wear-and-tear. Instead, I found that both potentiomenter/switch units were torn back off of the verticle preamp PCB. The whole scope inside was immaculate - no dust or residue on either the chassis parts or any of the PCBs, so I surmised that the unit had been disassembled, sent through an ultrasound bath, reassembled, and then per mishap bumped severely against something hard which rammed the vernier rods into the unit, tearing out the potentiomenter/switch units.
After repairing the damage, I began to go through the funtional verification process when I noticed a "black hole" in the trace (see pictures). The "hole" only appears a trace crosses it, and the position of the hole is not affected by any of the control settings, so I suspect that the severe bump may have jolted some phyiscal part the CRT assembly out of alignment. But I have not been able to find any documentation on removal/replacement of the CRT assembly, and I do not want to jump too hastily into unfamiliar territory.
So here my question / call for help: has anyone seen this kind of anamoly before and/or does anyone have an idea of what may be causing it? The problem is not serious, but I would like to solve it if it can be done with reasonable effort, since the unit appears otherwise to be in a very good working condition.
Thanks for any helpful advice!