(Aaron, Corey, Jim)
Yesterday, Richard let us know that one of the TMS cable runs (see EX TMS Cable Table, here) was having shorting issues.
So, these cables are shielded. There is a plastic mesh on the outside of these cables, and under this is a "copper shield"; this shield runs the length of the cable and ends at pin 13. It terminates back at the chassis/rack & at end close to OSEM/sensor/etc. This shield should be isolated from ground (i.e. the BSC Chamber, for example).
Richard and crew discovered that there was a short in a TMS SUS cable runs & narrowed it down to the cable which runs four OSEMS, in other words:
in-air cable--> |feedthru| -------D1000225 s/nS1106816-------> |CB3| -------D1000234 s/n96-903------->
Aaron confirmed that there was no short in the In-Air Cable. We then went in chamber and disconnected D1000225 from D1000234. Aaron then checked for shorts at the air-side of the flange and still found a short. This narrows down our shorting issue between air-side of the flange and D1000225. Unfortunately, D1000225 is a seismically-responsible cable, which means it's on the Optics Table for a few inches, and then is taken up and dressed on the ISI for many feet with several cable clamps.
Jim investigated the one cable clamp on the table, and then moved to another part of the chamber to check an ISI actuator (because this actuator shared a clamp with our D1000225). We also had Aaron check outside to see if there was a short with the in-vac Actuator cable (If there was, then we could narrow down the short to a clamp where an Actuator and D1000225 were). The Actuator cable was fine, no short. So, this means we need to check clamps up on top of the ISI. We need to have the Dome off to do this. So this may not happen for a while since the Dome is ON.
So we are leaving as is. I reconnected D1000225 to D1000234, and Aaron reconnected the in-air cable to the flange.
Note: The in-air cable appeared to have a bent mounting screw & the head of the cable is pretty gnarled up (making it hard to use a screw driver on it). It should be replaced.
This is mostly just a reminder for work after the break.
We need to look at this in light of Betsy's/Rich's logs about the cable shell screws on the feed thru end of the cable, which we hadn't seen or heard about prior to going to the end-station this morning. Our tests earlier indicated that this half of the in-vac cable is the problem, and the cabling up on the ISI looked pretty good (nevermind the fact that it is now mostly inaccessible, and shell screw shorting is our only hope for a quick fix).