Summary 1) PDP-8 Symptom was start/load addr/deposit/exam/cont switches did nothing. Tracked down to bad R302 dual delay/one shot board. Swapped with a spare. Ran diagnostic set and no more problems found. Left normal demos loaded and discussed how to run lunar lander if people want to also demo it. Has long load time from teletype. 2) TI Professional Symptom was keyboard wasn't working. Swapped with keyboard from my TI and it worked fine. Swapped original back and it worked fine. Wiggling things didn't change behavior. Later it was acting up again but didn't have time to investigate much further. Looked to be connection problem at computer end either the motherboard connector or the cable. 3) Xerox Star/8010 Normally it declared fault with Ethernet which we aren't using so use alternate boot key to bypass diagnostics. It is now ignoring the alternate boot key. Tried board from spare machine and it acted as alternate boot key was always down. Alt boot key goes to IOP card. IOP card installed in Connors machine worked fine. Out of time to investigate further. TLDR; 1) PDP-8 Some people were interested in learning more about troubleshooting and operating machine so used time to also show how I approach troubleshooting. Verified reported symptom and that panel lock was not active so pulled out scope and schematics. Looked for paths that would effect multiple front panel switches and found some signals weren't active and traced it to the R302 that starts the chain of pulses to drive the front panel operation. Tested all the diodes with a DVM since they are the most common failure. All looked good. Forgot my transistor tester so used the DVM to test the transistors. They all appeared good. Looked at trying to troubleshoot the card with scope but DEC only released the schematics for the cards but not the component location drawing. Vince has created layouts for a number of cards at https://so-much-stuff.com/pdp8/flipchip/flipchip.php but the early revision card didn't have a layout. Since I had a spare we swapped it in and adjusted the delays and I took the card home to repair. Transistor tester shows one transistor is bad. DVM also shows its bad so did something wrong when I was originally testing and missed it. Will replace transistor and test in my machine before next visit. Showed how to load and run the diagnostics and the Focal lunar lander game. Also showed the board I made to allow the serial port to run at 9600 baud instead of the normal 110 and the current loop to RS-232 board so I could send tape images from the laptop to speed up testing. More of these can be made if others are going to do maintenance. Also noted that the intermittent issue with the machine going into run on power up seems to happen when the machine has been off for a little while. This has been on the todo to fix for a while but normally it won't reproduce after fixing the more serious issues. Probably best to start with this next time. Working around by setting switches to stop at power on/off. Computer corrupts memory if it starts running on power up. 2) TI professional Later when we noticed keyboard was acting up again the symptoms looked like a bad connection at the computer end of the keyboard cable. Didn't have time to verify it its the keyboard cable or the connector on the motherboard. Noticed some clicking from the speaker that changed with wiggling the cable. Likely this means the power or ground signal is the cause and the transients from it going open and closed are getting into the audio. Left keyboard disconnected to avoid the clicking. Didn't have time to investigate further. Note keyboard is not compatible with standard PC keyboard. 3) Xerox The machine has 4 digit diagnostic display and reset and alternate boot buttons to control and monitor boot progress. It was hanging on Ethernet loop test fault (0332). Nothing was connected to AUI port. I brought stuff to connect to see if that would get it past the fault. With AUI transceiver to switch it did get past the fault but faulted with 0323 which is real time clock (RTC) not set. Connor figured out that the keyboard skip/next key would make the machine continue past blinking fault codes. The machine then hung at 0501 which is starting to read the TOD clock. This wasn't a blinking code so couldn't get past it. I also tried booting other images such as Interlisp. It started to put up a desktop then also hung on TOD. The alt boot switch goes to the input output processor (IOP). We pulled the board from the machine in the warehouse and it instead acted like the alt boot switch was always down. This was the symptom seen with that machine when we were testing VCF's two machines originally. The IOP worked fine in Connors machine. Some other fault is causing the problem. Need to investigate schematics and see what could cause problems with reading the alt boot switch and real time clock. Tracing signals Will be a pain since don't have good access for probing signals. The power supply output good lights were all on. I didn't check with DVM. Probably would be good to dig up the test connector pinout to check them. Some comparison with Connors's machine with VCF's was done and with different disk images. The hardware looked to be similar but some of the behaviors and faults were different. Didn't capture details on these tests.