J. Kissel, F. Clara, M. Pirello
D2300167 Record of LHO DC Power Supply System
S1301897 VDC-C1 Rack S-number
S1301868 SUS-C1 Rack S-number
WP:12962

In support of last week's CER / Electronics / Rack changes to move the Beam Splitter electronics over from the susb123 / SUS-C5 & C6 system to become a part of the expanded susb2h34 / SUS-C1 & C2 system (LHO:88765) we needed more +/-18V DC power to support the incoming chassis into SUS-C1. 

We already knew in 2023 that SUS-C1's +/-18V power supplies in VDC-C1 U2 were already supporting a lot of current draw from the existing MC2, PR2, SR2 chassis in SUS-C1. However, the original 2023 plan (see page 10 of Part II of G2301306-v9) involved stretching power cables across from the chassis in SUS-C1 to the empty spigots available in the relatively unpopulated SUS-C2's +/-18V power rail. But, when the day came, we'd not remembered that plan, and the existing chassis power cables weren't long enough to make the rack jump. 

So, we did a "good enough for now" solution: installed a new +/-18V power rail into SUS-C1, and still powered it with the supplies for SUS-C2 in VDC-C1 U6, but connected the new SUS-C1 rail to it by modifying the junction box on top of the SUS-C2 rack. 

In doing so, we identified that the existing power supplies for SUS-C2 were on the list for replacement, so we replaced the U6 power supplies before making the connection.
               +18V           -18V
Removed       S1201904      S1201905
Installed     S1201909      S1201908

I've updated the VDC-C1 rack S-number, and SUS-C1 rack S-number to reflect these changes, but haven't touched the Record of LHO DC Power Supply System (links to these things above).

Prior to replacement, we measured the voltage supplied to be +18.81 [V] and -18.66 [V], and set the new supplies to that voltage after install. The new supplies measure the current draw what it supplies (All of SUS-C2 and the BIO chassis and Coil Drivers for the Beam Splitter) to be ~10 and 8.5 [A].

Ideally -- and what may be necessary -- is to install a new set of power supplies to support these two racks: we still need one more TACQ driver in SUS-C1 (which will use these VDC-C1 U6 supplies), and the planned, fully outfitted SUS-C2 which includes 7x more chassis. I bet those chassis will draw at least, if not more than, 5 [A] worth of current at +/-18V.

Pictures relevant to this install attached.