Date: Thu, 23 May 1996 15:29:15 -1000
From: Doug Toomey <toomey@herschel>
To: techgroup@herschel
Subject: nsfcam repair
 
Hi
 
Two problems were found with NSFCAM's filter drives.
 
Filter wheel drive
 
The fiberglass shaft and helical couple were both broken.  They broke because
the clip holding the K filter had caught on an edge of the filter wheel housing.
THis filter was not touched during the Hilo work.  The best guess is that the
clip caught and jammed the wheel causing the coupling to break.  The broken
coupling acts like a rachet probably causing the clunking noises that were
heard.  When the software reversed directions the coupling could grab and then 
broke the shaft.  The spacer on the K filter was filed down and the clip is now
low enough.  A new shaft was installed as well as new couplings.
 
CVF wheel
 
The two screws used to hold the new grism were too long and stuck through the
back of the wheel.  THis rubbed on the nozzle track causing excess friction.  
This was probably the cause of the cvf missalignment that Sandy saw.  The 
nozzle track was not tight from the Hilo work and didn't help things any.
 
Detector spots
 
We could not see the detector surface without a complete dissassemmbly.  We 
chose not to rip it apart.
 
Darryl and George are just buttoning it up now and will put it on the pump.
THe operator will cool it tommorrow night.  I believe that if we stay on track
George and Paul will come up Sunday to mount it.  There is a chance that it will
be ready Sunday night.
 
 
Doug