PULL OUT THE DETECTOR CARD

Last update: August 1997

This is another (last) difficult step. Also, you will need to be creative and careful one more time: when we free the detector card from the back of the box (instructions below) it will drop to the bottom of the box, carrying the thin wires with it. Having the box tilted helps, but horizontal is better or use small pliers (the kind that presses by default) to hold on to the card so that it doesn't drop when you free it.

Unscrew the upper cold strap from the back of the box.
Unscrew the 4 screws that tie the the G10 plate to the back of the box. Those are labelled A, B, C, D in Drawing 4. Remember which set of four holes at each corner is being used, since that determines which quadrant is aligned on the optical axis.

Now the detector assembly is tied to the G10 plate, but free from the box. Either now or in the following
step is when the detector card will want to drop down if you are holding things vertically.

Unscrew the 4 more inner screws in that same G10 plate, labelled 1, 2, 3, 4 in Drawing 4. Keep one of these screws handy, you may need it shortly.
Now you can tilt back the G10 plate somewhat, and gain access to the screws that attach the lower cold strap to the cold finger. Remove them. This is a pain, and putting it back is a bigger pain even, but you'll manage. Then, you can separate the G10+cold strap and set it aside.
The next step is to pull out the detector card. Note that it is permanently attached by the red thin wires to the connectors in the cross-brace, so it will not go very far. My trick is to flip it as I pull it out so that the front (incoming light) faces up, and set it on the back of the box itself. This is again why being horizontal helps. Be careful not to pull on the cu-c wires as you take the card out, and not to press on them when you set it on the back of the box.

Now, that thing at the center of the card is the NICMOS3. It is sitting in its socket, and is covered by the "detector cover". The detector cover is in turn being pushed down by a copper squared-ring spring held by
4 screws.

Eliminate the 4 screws that hold the copper square-ring spring. Do them so that the spring doesn't fly into your eye and back down on top of the detector. Another trick at this point is that you can use one of the free holes on the detector card from this last step to actually secure the card to the back of the box using the screw that you kept handy in (5-c), and one of the holes in the back of the box.

That way it won't wiggle around, or fall off. But this may not be worth it if you are not going to do a lot of work on the card.

That's it. Go take a shower.

Now simply put the replacement detector cover in place, being careful to properly align the inner recess with the detector and its socket.
Then, put the spring back in place. Turn the screws until the spring is pushing on the cover nicely, and symmetrically.

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