Reports until 11:56, Thursday 06 March 2014
H1 ISC
stefan.ballmer@LIGO.ORG - posted 11:56, Thursday 06 March 2014 - last comment - 12:47, Thursday 06 March 2014(10585)
Photodiode concentrator Channel 4 (D1201345, S1300240) busted
The monitor point reads 13V, and the ADC reads -20000cts, even with the input terminated.
The busted channel (CH4 is used for the green y-arm transmitted power, and was temporarily used for ITMY dither alignment by hooking it up to POB18_Q.
Comments related to this report
daniel.sigg@LIGO.ORG - 12:47, Thursday 06 March 2014 (10586)

These are current amplifiers with a -5V dc bias and 1k series resistor. They are only intended for unamplified photodiodes! Grounding them produces a 5mA current which can rail the output (depending on the selected gain). D1200543.