M. Pirello, A. Ramiez, E Castrellon
Work Permit 6271
Per ECR E1600292 we applied the VCO capacitor mod to all 5 VCO's in the corner station and one at each end station. This process includes replacing the 10nF capacitors on C79 and C80 with 2uF capacitors, and checking the voltage rails to verify elimination of the 420kHz oscillations.
Corner Station Units:
S1200563, S1200559, S1200560, S1200564, S1200558
End X:
S1200561
End Y:
S1200566
Notes:
End X, there was a very inconvient clean room pole directly in the path of extraction for the VCO from the rack. We had to relocate 2 chassis to angle the VCO enough for removal. All chassis were put back in their original positions before leaving.
End Y, this VCO required more capacitance to remove all of the 420kHz noise on the -24V Rail, with the addition of a 2nd 2uF capacitor, the noise was eliminated.
After going through my notes, the following should also be logged.
VCO S1200563 is outfitted with a PLL board. This board is attached to the existing board via an SMA-T connector on the Low Noise VCO Board. This connector was very loose when we opened up the chassis, and the end that is supposed to connect to the PLL board was disconnected and wedged between two VCO modules. The SMA was very loose here. We showed Richard this and he advised us to remove the SMA-T and the SMA jumper cable which was disconnected, we then used an SMA cable torque wrench to ensure proper torque on the connectors.
When we worked on the 2nd PLL VCO chassis (S1200564), we noticed that the SMA-T was torqued, and the SMA jumper was attached to the PLL board.