DATE
MAINTENANCE
Sep 2006
refrigerator failed (stage3 at xx K); removed from C11, shipped to Berkeley
Oct 2006
found jammed clothespin on inlet valve; replaced valve plate
baked displacers
new Scotch yoke bushings and Kap-Seal
new stage3 seal
installed thermal stabilizers on stage3 and on mixer blocks
cooldown.01nov06 shows 2nd stage problem
02 Nov 2006
replaced stage1 and stage2 seals; phenolic has slight chip just above stage2 seal
cooldown.03nov06
at 30 rpm, mixerB is at 3.2 to 3.35 K
08 Nov 2006
dewar installed on C13
22 Apr 2008
dewar removed from C13, brought back to Berkeley to swap in HIA mixer; found about half a teaspoon of water on displacers; vacuum baked displacers, replaced stage 1,2,3 seals; removed sight glass and wiped oil off inside, but did not fiddle with Scotch yoke bearings
29 Apr 2008
tested HIA mixer; refrig running at 56 / 13.5 / 3.1 / 3.4 / 3.2 K
07 May 2008
dewar installed on C7
05 Aug 2009
dewar removed from C7; wiring problem to 1mm mixer
Aug 2009
removed "good" motor/displacer assembly 5746, installed in dewar7, cyl 5093, which now cools well (52 / 11.8 / 3.0 K); unfortunately "bad" motor/displacer 5093 works poorly in dewar5, bottoms at (53 / 13.8 / 4.2 K) in test [917]
Sep 2009
[918] bottoms at (52 / 19.4 /4.2) after swapping in spare 2nd stage from OVRO
[919] bottoms at (56 / 18.9 / 4.2) with another spare 2nd stage
[920] bottoms at (63 / 13.6 / 4.0) with original 2nd stage, new 2nd stage seal
[942] retest Apr 2010 bottoms at (59 / 13.3 / 3.9)
16 Apr 2010
removed 69 g Er3Ni spheres from stage3 displacer (#30), replaced with 67 g HoCu2 spheres;
[943] bottoms at (60.1 / 13.2 / 3.30);
stage3 runs at 4.03 K with 50 mW load, 4.63 K with 100 mW load