After verifying that the channel 3 of the Hammeg28 power supply was not working anymore, we replaced it with a spare one (Hammeg29) as shown in the attached figures. We have set the configurations of Voltage and Current as previously for each of the 4 channels, i.e., 12V for CH1 and CH2, 15 V for CH3 and CH4 and 300mA of current for all of them. We also reattached all the cables as they were before. 

I have temporarily restarted the PCal laser around 10h UTC.

• figure 1: laser still off.
  • Noise on Tx_PD1 is larger than usual, and there is large noise at 50 Hz.  (it should be similar to the noise of Tx_PD2 in principle).
• figure 2: laser switched on at 1.3 W, loop closed on Tx_PD2. 
  • Tx_PD2 and Rx_PD1 signals look good, around 1.3 W as expected.
  • but Tx_PD1 signal is not at its correct value (0.04 Winstead of 1.3 W) and still has large 50 Hz noise.

--> to be checked if the banana connectors to the power supply are properly connected on the power supply, or if some wire is badly attached (as seen and fixed in 2023) ?

Note that the calibration lines are not injected : this is because they are enabled only when the power monitored by Tx_PD1 is high enough, and Tx_PD1 is below the threshold with the current issue.

Meanwhile, I have switched off the NE PCal laser.

The NEB and WEB PCal fast server configurations have been updated to allow to use or PD1_DC or PD2_DC to allow the PCAL lines injections.

Operations performed at 2025-12-12-04h03m51-UTC

After these operations, the PCAL loops were succesfully closed with the PCAL lines injected 

• PCAL_NEB: using Tx_PD2_DC instead Tx_PD1_DC as the power on Tx_PD1 is lower than usual 
• PCAL_WEB: using Tx_PD1_DC as usual . By mistake Tx_PD2_DC was set, restored to Tx_PD1_DC at 2025-12-12-09h52m08-UTC