Unfortunately that is a pretty typical solder joint for an M100 it is OK. One thing you might want to look for is corrosion caused by flux residue that was left behind after the manufacturing process. It looks like a copper brown deposit but might hide a damaged track. I have worked on a few Mobos where the track has tested open circuit or very high resistance due to the residual flux corroding the track over time. Look particularly around the OPTROM socket or ROM socket where flux could collect after a bad¹ wash. Quite a lot of the tracks to the PIO are routed under the flash socket if they are bad then the PIO might not be working properly which will impact most of the board.
It could also be a failed component which after 35years would not be unreasonable. Some output stuck high or low can cause issues elsewhere that can be misleading. From: M100 <m100-boun...@lists.bitchin100.com> on behalf of Chris Fezzler <fezz...@yahoo.com> Reply-To: "m...@bitchin100.com" <m...@bitchin100.com> Date: Saturday, August 1, 2020 at 9:35 PM To: M100 Mailing List <m...@bitchin100.com> Subject: [M100] Narrowing down issue, I think > Please look at the PCB pic here. It is of the option rom socket from the > component side. > > Those to points are not supposed to be soldered together, are they? > > My LCD issue may be related if they are not. > >
