Yes it could be a broken trace they are very fragile, the boards are very low quality and 35+ years old :)
There are quite a surprising number of things out there for the 100/102 from modern software to new hardware add on designs. There are a few repair videos on YT if you need extra information. From: M100 <m100-boun...@lists.bitchin100.com> on behalf of Scott McDonnell <mcdonnell.j...@comcast.net> Reply-To: "m...@bitchin100.com" <m...@bitchin100.com> Date: Wednesday, December 16, 2020 at 8:06 PM To: "m...@bitchin100.com" <m...@bitchin100.com> Subject: Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column > I think you may be right. So, I went ahead and did that since it seemed quick > and easy with a good desoldering pump. Unfortunately, I think some traces were > damaged despite my being careful and using a good tool. At least one was > obvious, but I didn¹t spot it until after I was finished (means I probably > caused it.) I fixed that one, but I get nothing now so I suspect there are > more I can¹t see with the naked eye. I will need to take the meter to the > lines tomorrow and check for broken traces. Perhaps I blew a barrel from > bottom to top side and will need to fix that. Traces seem very fragile. > > Anyway on the right track now. I would still like to replace my ROM to take > advantage of the fact that this model is compatible with a 27C256. These are > my very first M100¹s, so I just don¹t know what is out there or where to find > them. I tried looking through the Club100 site and I have probably looked at > the thing I want a 100 times and just not recognizing it. Would really > appreciate a suggestion. > > Goodnight folks. Thank you for putting up with me tonight! > > Scott M. > > > From: B4 Me100 <mailto:b4me...@hotmail.com> > Sent: Wednesday, December 16, 2020 10:01 PM > To: m...@bitchin100.com > Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a > column > > > Hi > > > > I suspect the standard RAM is probably bad and the first place to look. I > would pull that one out, as well as all the other RAM, and try another good¹ > one in that location. It should boot beyond the confused LCD screen. I > doubt the ROM is bad if it was broken nothing would work I have never seen a > bad ROM but have replaced quite a lot of ceramic RAM modules I think I have > 7 bad modules on my bench, 4 from one machine :) > > > > The standard RAM module, the one that is soldered in, is where all the data is > stored that controls the system. If it is bad nothing works or at least it > will be flakey. Removing the other socketed RAM will not impact the system > they are optional and are not needed to run the machine. The machine appears > to boot quite far into the ROM and I think after the LCD is turned on it > starts to configure the standard RAM ready for file storage and general > program use, which is where it appears to be failing. > > > > I would be tempted to replace all the ceramic OEM RAM modules with more modern > versions just to make sure the machine is reliable for your application. I > have had one machine where they died in sequence almost. > > > > Possibly first recap the boards to make sure the voltages are healthy and look > for corroded traces - another very common fault. > > > > > > From: M100 <m100-boun...@lists.bitchin100.com> on behalf of Scott McDonnell > <mcdonnell.j...@comcast.net> > Reply-To: "m...@bitchin100.com" <m...@bitchin100.com> > Date: Wednesday, December 16, 2020 at 6:28 PM > To: "m...@bitchin100.com" <m...@bitchin100.com> > Subject: Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a > column > > >> >> Well, good news and bad news. I cracked open the working M100 and they are >> different generations of boards, so the ROMs are different. The good news is >> that the ³bad² M100 has the type of ROM that can be replaced with a 27C256. I >> only have some 28C256s sitting around so I ordered some 27C256s (don¹t want >> to bodge the board to make a 28C256 work just out of impatience). >> >> As soon as I can find a ROM image (can anyone point me to the location of >> these and recommend an updated custom ROM?) I will burn an eprom and give >> that a try. I do have a feeling that this is the problem. >> >> For reference, my working M100 has board PLX110CH1X and the bad M100 has >> PLX110EH1X. The RAM modules in the working unit also appear to be >> after-market and my PIA is socketed, so someone worked on this before. >> >> Bad is on the left, good is on the right: >> >> >> >> >> >> From: Scott McDonnell <mailto:mcdonnell.j...@comcast.net> >> Sent: Wednesday, December 16, 2020 8:43 PM >> To: m...@bitchin100.com >> Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a >> column >> >> I should have added that the reason I suspect the one RAM module soldered to >> the board is that I tried removing the other 3 (this has all 32K of memory >> installed) and nothing changed. My next step was to desolder the RAM module, >> install socket strips and then try one of the other RAM modules in the main >> slot. >> >> I am also planning to try taking the ROM from my working M100 and installing >> that in the non-working unit to see if it is the ROM. >> >> Any other ideas would be appreciated. >> >> Scott M. >> >> >> From: Scott McDonnell <mailto:mcdonnell.j...@comcast.net> >> Sent: Wednesday, December 16, 2020 8:06 PM >> To: m...@bitchin100.com >> Subject: [M100] Model 100 Repair - Keyboard not responding,LCD missing a >> column >> >> I mentioned before that I bought two Model 100s and that one of them is not >> working. Here is a description: >> >> The computer boots sometimes. When it doesn¹t you get just a dark screen. >> Turning on and off a few times, you get the menu. However, only Schedule is >> populated (in the first slot which would normally be BASIC) and there is no >> ³SELECT² at the bottom. No response from any keyboard keys. >> >> The above leads me to believe that it is not really that the keyboard is not >> working, but that the computer encounters a fault while loading the menu and >> never completes to the point that I could use the keyboard. That leads me to >> think maybe a faulty ROM or possibly the one RAM module that is soldered to >> the board. I wonder what others might think? >> >> Second problem: >> The LCD is missing a column. I got brave and disassembled the LCD to clean >> the contacts. The good news is that I think I fixed that missing column. The >> bad news is that now the LCD is all jumbled mess. I don¹t think it is >> alignment since some text displays perfectly fine is just the right spots. I >> think it is a lack of pressure. Planning to install some thin foam inside the >> metal surround to create more pressure on the LCD contacts. I think the metal >> twist tabs are just not cutting it anymore. I will update whether this works >> or not. >> >> I plan to recap both of these and replace the NiCad batteries, but I don¹t >> believe that either of them currently have any issues with those parts. If >> anyone has experienced the above problem, I would very much like to hear what >> you have done to fix it. >> >> Scott M. >> > >
