Jonathan, Jeff, Tony, Dave:
Following the upgrade of h1iscex 18bit-DAC upgrade to a 20bit-DAC Tuesday 02dec2025 we discovered the 20bit-DAC was not outputting any voltage.
Wed 03dec2025 Tony and I went to h1iscex to replace the suspect 20bit-DAC with the second DAC which was removed from the h1susex upgrade Tue02dec2025.
All while H1 was locked, we powered down h1iscex and its IO Chassis, pulled the chassis from the rack, took its lid off, replaced the 20bit-DAC and powered the chassis up while it was open.
I powered up the computer and auto started the models. H1 lost lock soon after the IOP model started running (possible Dolphin IPC minor break in transmission?).
We verified that the replacement 20bit-DAC was working, looking at both the DAC_chan7->ADC_chan30 DUOTONE inteface card loop back and h1calex drive of DAC_chan6.
We closed the chassis and pushed it back into place.
| Suspect broken 20bit-DAC (removed) | 190219-10 |
| Replacement 20bit-DAC (installed) | 150311-01 (S1700286) |
Note that both of these 20bit-DACs came out of h1susex during its upgrade to LIGO-DACs Tue02dec2025. I'm not sure which one was driving the PI signals, and initially I chose the 2019 card for h1iscex over the older 2015 card.
Also note that the 2015 card has a LIGO S-number tag, the first I've seen on a GenStd IO card.