A quick check is to measure the voltages at the VDD and VEE test points marked on the motherboard, they should be a strong +5V and -5V respectively. From the fault you are reporting it sounds as if the main motherboard voltages are bad. The NiCd should be about 3.7V when the power is off. The ‘corrosion’ looks like damage from leaking electrolytic capacitors - very typical for the Model T and any old/vintage equipment.
The next step looks like replacing all the electrolytic caps on the board as well as the NiCd. Fortunately ….. there is a video on YouTube on how to replace them by Jeff Birt (the link has been posted on the forum but I could not find it), that should help with the replacement :-) I have seen this behavior quite a few times, on old Model 100s in particular, the first step is to get the motherboard voltages clean and stable. There may also be broken/cracked solder joints on the board that need to be repaired later - the PCB build quality was not the best. :( The faint buzzing sound is possibly the DC/DC power transformer overloading for some reason. On 6/1/19, 5:37 AM, "M100 on behalf of Eric LK" <m100-boun...@lists.bitchin100.com on behalf of tr...@lefauve.org> wrote: >Hi, > >I'm still waiting for my replacement Ni-Cad battery but I've been >continuing using my M100 without any other issue... until tonight. > >When I turned it on, the "low battery" light was on, and the date >displayed on the first line was wrong: ◥5ÿ 00,1919 Sun 00:00:00 >I switched it off and on again, and it stayed this way. That's when I >noticed the keyboard wasn't responsive. Also the first 3 characters >flash every now and then (here is a 11 seconds video: >https://eur04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.yout >ube.com%2Fwatch%3Fv%3DjjUw2XpB0Gw&data=02%7C01%7C%7Cb1a46fe150a94d4e06 >9508d673dc2a57%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C63682378676931 >1870&sdata=TM%2B7eX8tPEbOMq67EjWHp8Y%2BEaa4xJv1LSkKFzoGS%2BM%3D&re >served=0 ; it happens around 00:03) > >I verified the voltage of the AA batteries and found 5.9V. Should be >OK but I still changed them. >Now the first line displays something like this: ros ??,1920 ñ)s ??:??:?? >...and the keyboard is still non-responsive > >I tried the reset button, which had no effect (the computer restarts >in the same state), and the whole reset (Ctrl+Break+Reset), which >removed all files from the ram filesystem but it's still stuck. > >After a quick look inside, the Ni-Cad battery didn't seem to have >started to leak, and I measured about 4.9V to its pins; I also noted a >faint buzzing sound coming from the LCD area while it was open. > >I also tried to switch the "memory power" switch off, remove the >batteries, replace the batteries, switch everything on again... same >result. > >At this point, I'm out of ideas... Any suggestion about how to >diagnose and fix this problem? > >Eric > >PS: There is a kind of battery leak damage around a screw on the >motherboard, but it's nowhere near any battery (it's located on the >left of the power switch). I noticed it when I first opened it a few >days ago, and I planned to give it a clean with isopropyl Alcohol when >I'll change the Ni-Cad but I didn't touch it yet. Could it be related >to today issue? Here is a picture : >https://eur04.safelinks.protection.outlook.com/?url=http%3A%2F%2Fpics.lefa >uve.org%2F20-32-45.jpg&data=02%7C01%7C%7Cb1a46fe150a94d4e069508d673dc2 >a57%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636823786769311870&sd >ata=Mrq3ifSaeZdGkCk8imGPxQqDsg3fDTxsBdgV%2BV2OiEE%3D&reserved=0
