Fil, Ibrahim, Betsy, Oli

Fil conducted grounding loop checks for the BBSS M1, M2, and M3 satamps. Grounding was found for SUS_BS_82 pin 23 and pin 10. After some issues, we managed to replace the grounded QOSEM with a working one, which we later aligned (see Ibrahim's alog 90838). BS M1 F3: was S2600013, now S2600016

SUS_BS_82 is the cable for CH3 (F3) and CH4 (SD), and pins 23 -> 10 are the coils for F3, so there was an issue somewhere between the satamp and F3.

Cables that Fil tested that aren't grounded are:

• SUS_BS_81 - BS M1 CH 1-2 (F1, F2) satamp
• SUS_BS_83 - BS M1 CH5-6 (LF, RT) satamp
• SUS_BS_84 - BS M2 satamp
• SUS_BS_384 - BS M3 satamp

Testing SUS_BS_82, all pins looked good except for Pins 23 and 10. Below are their readings:

Checking wrt Chamber:

• Pin 23 to Chamber ground: 33-35 Ohm
• Pin 10 to Chamber ground: 0 Ohm

Checking wrt Rack:

• Pin 23 to Rack ground: 45 Ohm
• Pin 10 to Rack ground: 80 Ohm

Flipping the pos/neg leads and checking wrt Rack:

• Rack ground to Pin 23: 120 Ohm
• Rack ground to Pin 10: 84 Ohm

After we found out that F3 is grounded to the chamber somewhere, we went in and unplugged F3. Once it was unplugged, we tested the cables to see if we were still grounded to determine if it was an issue in the wiring or in the QOSEM. The cables were not grounded, which told us that the issues was with the QOSEM. The installed QOSEM at the time was S2600013. We removed it and installed S2600025, which did not have any grounding issues, but the LED wasn't working on it, so we had to remove it. We then installed S2600016, which was not grounded and was also working fine. Later we centered it in X (90838).