Some notes about replacing CCDs
JDM, CP and SM Sep 2000

1. Let it warm up so that water doesn't condense on surface
2. Ideally one should open vacuum by backfilling with dry N2, but this not easy at Mt. Hopkins (we didn't do it)
3. Remove all screws from around rim, including 2 difficult to see ones that are embedded inthe heat transfer block (from back).
4. Use Grounding strap
5. Remove card which contains chip from the unit by removing the holding posts (and bolts/nuts). Pull off carefully, but it may stick due to heat conduction go on the back of the ccd itself. At this point it could slip out
   of your hand and land on optics table CCD-down.
6. Use "special" tool to pry out the chip; be patient and calm. Note location "key" w.r.t. the card (so you know how to orient the new chip). Alternatively, you can replace the whole head electronics and CHIP.
7. Pop in new chip and put everything back together. We used Thermalcote heat sink grease ( which is supposed to work down to -40 F/C.
   Note that housing is spring loaded, so one has to push while re-connecting the CCD unit to the vacuum housing.
8. Pump out with leak checker for many hours.
9. Cool down and check to see if it works. Note: we had the experience that at least one CCD chip can detect light, but can not form a proper image. Its not known if this is due to problem with CCD head electronics or the chip.

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