Fil, Luis, Camilla. FRS 26828#c11 Previous troubleshooting in alog 74951, 74750.
Today Fil went onto the HWS table and verified the HWS cameras are connected straight to the external power supply (photos in FRS26828#c8) via cables connected together. The HWS camera fiber CLink box is powered by the HWS breakout chassis D1200934 (originally designed to power cameras too).
Fil theorized that the HWS grounding is due to the power supply to fiber CLink connection grounding the cameras! With a multi-meter, we verified the HWS camera is grounded to the table when the CLink power cable is connected but when we disconnect CLink power, the camera is not grounded to the table (has Kapton tape and plastic bolts).
Step 1 (Completed): I removed the grounding cables from the HWS external power supply as Luis suggested in FRS 26828#c11, to avoid us holding the cameras negative terminal at mains ground. Photo of current connections attached.
Step 2 (Planned): After verifying step 1 doesn't effect the combs (need overnight "quiet" data), Fil will make a new cable to power both the camera and CLink's via the external supply (14V is fine for both).
Preet, Camilla
It appears changing the cabling of the external power supply has removed/reduced the comb: compare blue trace before cabling change to red trace afterwards change in attached plot.
To verify this, we undid the cabling change, back to the old configuration this morning at 9:30am and turned the camera back to 7Hz each, we'll later check if the comb reappears.
Preet, Camilla, FRS 26828
With the swap back to the old cabling, we confirmed that the comb came back, see Feb 22nd data in attached plot. This morning I changed the cabling back to the "quiet" version, photo attached.
Question for others, is the old cabling expected to push noise into DARM or is there an unknown coupling? Tagging PEM, CDS, Detchar.
Have you try using a different power supply or low the voltage to +12v? the camera also works with +12v and the rcx c-link only required +5v supply.