Appendix E - Errata

Oopses, bungles, mistakes, and misfires.

• On circuit board "NRAO ENCODER FINE 5-19-99", R8 is connected to the wrong side of U6. This shouldn't have any effect, but noise performance could suffer.
• When making a cable to connect circuit boards "NRAO ENCODER FINE 5-19-99" and "ENCODER COARSE CARD" be sure to match CSEL and CLK. Their pin positions are swapped.
• Be sure to match the transfer ratio of the resolver to the output on the "ENCODER COARSE CARD". If you are using a 1:1 resolver this will require only one lead of the rotor be connected to J1 and the other lead to power common.
• Slowly rising power supplies will lock up the PIC16C55 chips. The production version of this system uses the MAX1232 supervisory chip to ensure clean startups.
• If you use the MAX1232 chip, don't do what I just did and make the silly mistake of not putting a pull-up resistor on the reset line. Now I have an embarrassing ECO on one of the production boards.
• Our Antenna Control Unit (ACU) has a data hold line that I did not implement in the prototype. It's rare, but occasionally the position data will be invalid. This doesn't hurt our performance, but does flag the data in the observer file which may lead the user to falsely assume the data is bad.