On Tue, Oct 13, 2020 at 6:50 PM Charles Hudson <[email protected]> wrote: > > and then checked the PSU voltage and replaced the AAs as first steps.
There are multiple voltages from the PSU; were they all okay? (+5Vdd, -5Vee, +3 to +5 Vb) > after reassembly I inserted a fresh set of batteries. I must have left the > power switch "on" because > when I turned it right side up I saw some characters on the display. This indicates to me that the memory power switch had been left in the ON position as well. This likely drained your memory NiCad beyond a safe point. It will need at least 24 hours to attempt to recharge. Again,the Vb (battery power rail) is critical here as this is what actually powers the RAM chips. No RAM == unhappy computer. You also mentioned re-seating the display cable. Does the connector look physically okay? The proximity to the AA compartment often leads battery corrosion to affect this cable. If this machine has *ever* had any battery leaks, this cable is suspect, along with most of the power supply circuit. Download the service manual from https://archive.org/details/TandyM100ServiceManual and follow the troubleshooting guides in the back, keeping in mind the age of these parts :) Good luck! -Josh
