ARNE Going Back Together

[Tom Droege <droege@wwa.com>]

I am now testing parts so that I can put ARNE back together.  I have big 
stacks of sick boards for Dan to fix when he comes in tomorrow.  I now have 
a test set up that I like.  I just have to work each board through it.

In spite of all my efforts to protect the cameras, I have determined (at 
some cost) that one cannot plug cameras with the power on.  Sigh!  A pity 
since this greatly slows down the testing.  This means that for some of the 
testing I have to reboot the computer many times.  For others, I have to 
restart the Stamp.  In each case it takes enough time to be annoying.  I am 
trying to work 20 sets of boards through the system.  This will not be much 
of a problem for you my dear users.  Of course a lot of testing can be done 
without the cameras connected.  But the final proof is always to get some 
images with cosmic rays and the Michael Richmond bumps.

I installed spacer rings in two cameras this afternoon.  Both cameras were 
leak tight for as long as I was willing to wait.  A big improvement.  It 
was just a question of getting all the tolerances right.  Still, I plan to 
pump dry air through the cameras.  Those of you with gas bottles will be 
able to flow the gas of your choice through the cameras, and then just 
unplug the gas fittings.  They seem to be vacuum tight for very long 
periods of time.

The TECs are still a pain in the neck.  Any shock to the camera is apt to 
kill them.  I will no longer glue the TEC stack together.  Just three 
grease joints.  I am using vacuum grease (The Dow Corning stuff) which I 
fill with silver powder to improve the thermal conductivity.  This seems to 
work OK.  This way I can take everything apart to replace one, or to 
temporarily remove it while I do something that shocks the camera.  (Like 
drilling the extra hole for the out gas flow fitting.)  Some of the TECs 
clearly died from my drilling and tapping a hole for the second 1/8 NPT 
fitting.

After having problems getting the TEC stack to stick together, I learned 
more about glue.  Now I cannot separate the broken bits of the TEC from the 
spacer block.  No amount of pounding seems to work.  Earlier a tap would do 
it.  That is why I shall order more spacer blocks tomorrow.

The general plan for the next week it to finish putting ARNE back together 
and move it out on the porch to take data.  MICHAEL is close behind 
ARNE.  Both are assembled to about the same state.  I have rebuilt enough 
lenses for both, and probably have enough cameras without having to wait 
for new spacer blocks.

Meanwhile the builders are here.  It looks like they will take the roof off 
the house Monday.  We shall see if they get everything done before the next 
rain.

Tom Droege