Fil, Daniel, Rahul

To further investigate on what is causing issues with ZM5 PSAMS (as reported in LHO alog 91120) I did a chamber side test (as per E2100371-v1) on the SQZ racks near HAM7 chamber. This time I was not able to drive the PZT voltage, which typically should vary from 0-200V. In this case it was showing -7V.

Next I connected ZM4 to ZM5 chassis to test the electronics chain - ZM4 PZT and SG voltage read fine. Next, I connected ZM5 to ZM4 electronics - again no PZT voltage. Hence, this ruled out any issue with ZM5 chassis and the issue seemed to be upstream of it (i.e. pointing towards the cables or in chamber).

To test the cables, at first Fil and I measured the impedence and capacitance of the PZT on both ZM4 and ZM5, as listed below,

ZM4 (PZT)- capacitance (pin 1,14 on db25)  =20.9 micro farad, Impedence = in mega ohms.

ZM5 (PZT) - capacitance (pin 1,14 on db25) = open circuit, Impedence = 2360 ohms  - which shows electrical shorting somewhere).

We unplugged the in air cable and in vacuum cable of ZM5 and the resistance was high - thus showing no shorting at the cables downstream of PSAMS. 

Hence, the PZT inside the PSAMS is shorting.