Anyone sitting on a pile of these or know where to find some? These were originally Dialco 507-3917 or Drake 11-507 based on what was installed in mine. 24V, 40mA, white. A total of 23 bulbs were dead on my TC01's panel. I've installed a pile of electrically/physically compatible bulbs that I happened to have, but they're yellow/orange and have a different visual design (the yellow lens sticks out 1/8" or so, whereas the orginals were flush). I'm honestly fine with using them but it'd be nice to have something that looks original. And a small progress update: Found that the IOT decode for READ STATUS B wasn't working, which is done on the W103 decoder at E/F19. With that resolved the diagnostics are behaving much more rationally. This took me much too long to trace down, but I learned a lot about how the controller works and found a fun (but ultimately harmless) bug in the Basic Exerciser diagnostic that threw me off for a couple of days... The Search Scope loop diagnostic shows block numbers going by in both directions so a lot of the drive and controller are working, but there's some glitchiness in bits 2, 5, 8, and 11 of the data so I need to trace that down; I hope it's not the tape head. - Josh