Spoiler alert for the next video! I've manage to get it all working by removing the encoder screen connection to ground. I had wrapped the screen around the cable where it enters the GX16 plug to ensure it was grounded (as James suggested) but it turns out the VFD noise is coming INTO the enclosure that way through the earth cable. Removing this encoder shield ground connection at the GX16 plug completely solved it.

I did look into buying more surface mount transistors but decided it was more hassle than it was worth and just bought a new one.

But since you asked it might be interesting to know if the original encoder could be saved so I've attached the schematic. It only shows the encoder output parts, not the internals. I broke it by connecting the Dupont connector backwards so the MCU pins are on the left, and the accidently reversed connector is on the right showing what went where!:

MCU pins left to right: My accidental reverse connection to:
0V_________________->A
+5V________________->B (NOK!)
index pulse Z________ ->Z
B _________________ ->+5V (NOK!)
A _________________ -> 0V

So you can see pulse B got the wrong signals and that appeared to be the most damaged channel.


Mine is not an Omron (I guess it is a clone) but it appears to match the one in the first column, 1024 P/R
https://www.ia.omron.com/products/fa...ification.html

Encoder:
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Circuit:
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MCU:
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