End Y

• We shut down the power supply and disconnected the HV cable from the power supply.
• The cable measured 12.9 ohms at the power supply end with the cable still attached to the ion pump at Y2-8.

Y2-8

• We disconnected the cable from the Ion Pump.
• The cable measured 0.1 ohms at the Ion Pump.
• The cable was measured with the Agilent Fieldfox in TDR mode, see plot1.jpg.  The 273m line is there to reference the end of the cable.  We were not able to see the beyond the short when looking from Y2-8.  We should have seen the end of the cable as from previous alog 28818.

End Y

• We returned to the end Y to measure the cable from the power supply, see plot2.jpg.
• The splice at 18m can clearly be seen in this plot as well as the cable end, which is what we expect to see from both ends.
• Richard ran the high pot and was not able to apply any voltage to the line without it going into fault, indicating a short.

Conclusion

It looks as if the ion pump end of the cable is shorted in or near the connector at Y2-8.  The cable near the end of the connector does not have strain relief and is slightly deformed.  Manipulating the cable near the connector did not change the cable VSWR trace, but it did change the measured ohms slightly.  More can be learned from disassembly of the connector housing without damaging the connector.  This should be investigated and the connector repaired / replaced next maintenance window.