[evlatests] Austin 1050 L-Band cycling problem

[Rudy Latasa]

Summary of L-Band 1050 cycling problem antenna 26 versus antenna 6
One 1050 temperatures cold and stable
One 1050 temperatures cycling up to 35K on the 15 K stage and 150K on 
the 2nd stage.

  After several months of cooling down and warming up the L-Band 
receivers on antenna 6 and 26, the temperature cycling problem with the 
new 1050 refrigerator has been narrowed down to the 15K (1st stage) or 
50K (2nd stage displacer). Below I have listed all of the possibilities 
that were suspected and looked at as the problem causing the temperature 
cycling associated with the new L-Band receivers.

1. Receiver Thermal short
2. Temperature differential (Night & Day)
3. Compressor Output Pressures and flow
4. Gas line restriction
5. Refrigerator Drive Motor Power
6. Refrigerator displacer clearance, timing, seal dimple and valve leakage

After discussing our findings with engineers at Austin Scientific 
(Oxford Instruments) on 06/06/2011, Austin Scientific requested that we 
send these two refrigerators back to Austin Texas, so that they can 
evaluate the two refrigerator driver/displacer units to determine if the 
problem is in the 15K or 50K displacer.

Antenna 6 and 26 will be warmed up on 06/07/2011, so that these 
refrigerators can be pulled and shipped back to the manufacture for 
evaluation.  Two new 1050 refrigerators will be installed in these two 
receivers and cool back down. I expect the temperature cycling to continue.