The good news is that for about an hour or so I had a 100% functional Altair 8800a..
MITS Altair 8800a closeup of broken A0 toggle switch. It's stuck in the 1 / on position
.. but Dan and I broke the A0 toggle switch during testing. It was bent and it was probably vulnerable to break so it did not take much to snap off. The system still works, but I can't deposit any values into memory that end in a "0" using the toggle switches. If I want to examine what's in 0000h I have to flip all of the toggles up (FFFFh), press "examine", and then "examine next" to get to 0000h. The lack of a functioning A0 toggle does not prevent me from using the system from a terminal or teletype as long as I have a bootstrapping monitor installed. A temporary setback only.
I decided to disassemble the front panel to get a better look at the toggle switch connection.
The MITS 8800a with lower chassis and front panel covers removed. Click image for larger picture.
After the lower chassis screws have been removed, the case slides away from the front panel. The next task is to remove the nuts that secure each toggle to the metal front panel cover. This picture shows some nuts removed and some loose on the toggles. Click image for larger picture.
The bare front panel for an 8800a. Click image for larger picture.