aLIGO LHO Logbook

H2 ISC

alberto.stochino@LIGO.ORG - posted 10:46, Saturday 09 June 2012 - last comment - 14:06, Tuesday 12 June 2012(3079)

ALS VCO has mismatched power levels

Yesterday Keita and I found that the output of the ALS PLL Phase-Frequency Discriminator unit was noisy and oscillating between its voltage rails.
We traced the problem back to a very noisy output signal from the frequency divider which provides the LO to the P-F Discriminator board.
Going up the chain, we found that the frequency divider unit was getting 0dBm instead of the nominal 13 dBm from the VCO unit. 

Apparently the VCO unit is not working properly. We removed it from the rack and took it to the corner station for inspection.
We are going to check it inside to find the cause of the mismatched power levels.

Comments related to this report

alberto.stochino@LIGO.ORG - 14:06, Tuesday 12 June 2012 (3092)

Link

Paul Schwinberg checked the board in the EE shop and found that the RF levels were actually correct.
It's not clear why the board was malfunctioning when Keita and I measured the levels on Friday.

We took the board to the end station and reinstalled it back into the rack.
This time the output level was okay: about +13 dBm.