With the new TiC#8 target installed on TM3, there was a ~7kOhm connection between TGHT/TBHT (A/B/C/D) and HV common. The standard electrical check on the module showed standard values, so it was assumed the problem was inside the target.

Started removing bolts/water connections one by one to see if any of them had an effect on the measurement. Found that disconnecting the multipin on the target from the mating connector on the source tray resolved the issue. Determined that the only way this could happen is if a spark cut through the insulation covering the multipin wires. Because of the way they are routed, they can touch the water lines and they are definitely touching waterline C, TBHT-. We do not typically check continuity of multipins to all water lines, just to HVC, so did not see this in the standard electrical check. Measurements verified that pin 2-4 was touching water line C, creating a short from TGHT/TBHT to HV common when the multipin connector is attached, since the pins are shorted to HVC inside the connector when they are not used.

Issue was solved by removing the target into the ante room, removing connector 1 all together since it was not used, and removing the grounding on the other pins, leaving only pin 2-2 connected for the anode.

In future we will change the IGLIS wiring so pin 2-4 is not used, and redesign the cable routing so it cannot touch the blocks. For the immediate term, we will add to the electrical check a check of each pin to TBHT/TGHT/COIL.