Type 111 Pretrigger Pulse Generator

Sean Turner

Hey all,

I was wondering if anyone knows of any factory mods that were done on the Type 111? I have an example that has a significant divergence from the schematic in the manual, namely around the fixed increment control. It's a little circuit mounted on an aluminum tab with a small ceramic strip on the inside and three socketed transistors on the outside, and there is a pot installed instead of the switch. I can't discern that this control has any effect on anything, and it is definitely not present in any scan of the manual or any pictures of the internals of other Type 111s.

Furthermore, it is factory quality assembly work, so I'm assuming it's either factory or someone who was really careful.

I put three photos of the circuit here (https://groups.io/g/TekScopes/album?id=261991). I annoted one of them to show the four places where the mystery circuit is wired into the main PCB.




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