Looks like we have a tradition going. This is the second "show and tell" note and I may keep it up until the film runs out.
We continue to run a production line. Mike and Dan have been busy, and have assembled a lot of stuff. Some of you will wonder why I have the production line going before I have one system checked out. Well, you have to strike while the iron is hot. In this case, you have to build while the summer help is here. During the winter I will think and test and measure. Everything has worked once, as the picture taken with the Ford chips proves. But there could still be a lot of bugs. Sigh! One cannot always work in the order one would like.
Figure 1 shows a pile of memory boards. Laying casually to one side is
192 Mbytes of memory. I was in this business when the whole world did
not contain that much memory. There is still a bug in the memory
design. Some of the boards write one byte off. We are not quite sure
whether the boards that appear good are bad and the boards that appear
bad are good, but we will eventually find the problem. We have not
really looked for it yet.
Figure 2 shows a pile of stamp - scanner boards. Most of these have been
tested and work. Possibly one or two scanner sections have a problem.
Figure 3 shows a pile of ADC boards. None of these have been tested, but
an earlier revision of the pc board worked, so I don't expect there to
be any problem with these. Tom says confidently. (I was raised
reading Tom Swift books.) Well, this is the heart of the system, and
it is where we will have noise problems if we have them. Still I have
made a lot of ADC systems work in my time, and if these 20 boards
should all fail to work I would still be batting over .990.
Figure 4 shows Mike stuffing a motor board. Many of these have been
assembled, and a few have been tested. Lots of features on this board
have not been tested, like the limit switch inputs. But it is a
pretty simple board and should work.
Figure 5 shows Dan repairing a stamp-scanner board.
Figure 6 shows a stack of camera head boards.
Figure 7 shows camera heads at their glue station. First we wire up the
connectors, then we pour epoxy into the back of the connector to make
a pretty air tight connector. Surely not vacuum tight, but good
enough to reduce the water vapor infiltration. The trick is to do
something to the front side of the connector so the epoxy does not
leak through and gunk up everything. After trying many things, I
found liquid latex in a hobby store. We coat the front side of the
connector with latex and after the epoxy has set we can simply pull it
off. It wants to come off all in one piece.
Figure 8 shows a stamp-scanner and an ADC board sitting on the carriage
where we will mount them. Putting all the electronics on the carriage
greatly reduces the wiring that must come through the motion. There
will be a cover to offer some protection, but I operate on the
principal that you never let it rain on your telescope.
Figure 9 shows the cable bridge that brings the wiring through the
declination motion. You can also see where we will place the clamp
disk for the declination motion.
Figure 10 shows the cable bridge in the park position. None of the
cables make big bends due to a scheme thought up by Mike Watson for the
bridge. One section is held at a right angle, and this restricts the
motion so the bridge moves where we want it to. In this view you can
also see the power supplies and a junction box for the AC power coming
into the system. When we shipped the Mark II to Los Alamos, the
safety people cut the cord off it and would not let them operate it
until it was rebuilt. Sigh! I used good "bread board" technique,
including a real board. This design should be able to pass a
reasonable safety inspection.
Figure 11 shows the test set up for the Mark IV. To the left, are the
two computers. One for the memory board and the display, and the
other to communicate with the stamp. You will only need one if you
cam program in something other than QBasic. Behind the chair on the
floor is a garbage can with the cooling liquid and the pump. In front
of the chair on the table are the four Mark IV electronics boards laid
out for ease in testing. Under the red cloth is a camera head. To
the right is the mount sitting on a card table.
Figure 12 shows the four electronics boards as laid out for test. To the
left is the stamp-scanner. Next is the ADC board. The third board is
the stepper and servo motor driver board. At the right is the TEC
driver with its large heat sinks because of the power needed.
Dan and Mike go back to school next week. Then I will concentrate on getting a camera working. When the camera looks like it is working, we will assemble everything on the mount, and put it in "dead barny" and try to see stars.