Sounds like the cable for the screen might not be correctly inserted in the connector. You could revisit the cable and make sure it was not broken or cracked when the computer was re-assembled. The plastic ribbon cable is a bit tricky to re-insert.
The black screen (if the boot process is like the 100) means that the processor is trying to initialize the screen and just busy waiting for a response it loops waiting for the busy bit to clear to indicate the screen is present. The BASIC beep test will not work in this case as it it is in a busy loop waiting for the screen. The auto power on after power off could be caused by the same issue or it could be a separate problem. The new battery will need a little time to charge up for the 200 to work properly so perhaps let it charge for an hour or two and then retry. From: M100 <[email protected]> on behalf of ethan saul <[email protected]> Reply-To: <[email protected]> Date: Wednesday, June 17, 2020 at 1:31 PM To: "[email protected]" <[email protected]> Subject: [M100] Tandy 200 Black Screen > Hi all, > > Anyone know anything about Tandy 200 black screen of death? I have changed the > CMOS battery and tried a cold start using CTRL+SHIFT+BREAK+RESET. > When I power it on I hear a click from the speaker and the screen goes black > the contrast knob doesn't dim or darken the screen. > I have also tried getting it to go into basic and beeping the speaker with no > luck. The machine was working before the battery change however the old > battery was leaking so I had to change it. > There was no corrosion and the battery area was cleaned with Isopropanol. > Also the Power button turns the computer off and then back on straight after > every time I push it and when there is power from either the battery¹s and the > ac adapter. > Any Ideas what could be the problem? > > Thanks, > Ethan
