Did you ever actually do the cold reset 3-finger salute? I didn't see you say that you did. I don't remember what the keys are for 200 but it's in the manual and probably on club100 and bitchin100 too.
ctrl + break + reset or something like that. Mere power-cycle isn't good enough, you have to do that reset hot-key once after any crash or full memory power loss etc. Then after that you can use the power button normally. bkw On Thu, Feb 17, 2022, 9:35 AM Gsvacances Free <[email protected]> wrote: > Thank you for your reply Jeff ! > > The reset switch seems to work as I hear a click in the speaker but > nothing changes on the LCD. > So I’ll check that the reset line is going wherever it needs to. > > As for bus activity, I only checked at the CPU but not on various RAM and > ROM chips. > So will do it too and keep you updated ! > > > Thanks again for your quick reply ! > > > > Gilles > > > > *From:* [email protected] > *Sent:* Thursday, February 17, 2022 2:22 PM > *To:* [email protected] > *Subject:* Re: [M100] Model 200 with LCD all black from power on > > > It sounds like you are on the right track. The first three things I check: > PCR - Power, Clock, Reset. It seems you have already checked the first two. > If the reset circuit is not working the machine will not start up in a > known state and many strange things can happen. > > > > The next few checks: BADS - Bus, Address Decoding, chip Selects. You have > already checked for bus activity but double check that you are getting all > the bus signals to all the main chips. I had a PC-8201 recently where I > checked bus activity at the RAM which was fine, but there was a broken > trace to the ROM. If I had checked in both places at first it would have > saved me much time. If any off the address decoding/chip selects are > wrong/missing all manner of strangeness will occur. > > > > The black screen at power up is the classic symptom of the computer not > booting up. When powered up the LCD drivers will turn on every pixel. > During the boot process the computer will reset the LCDE drivers which > turns all the pixels off. Being stuck in this not booting state can be > anything from bad RAM, ROM, address decoding chips, etc. > > > > Jeff Birt > > > > *From:* M100 <[email protected]> *On Behalf Of *Gsvacances > Free > *Sent:* Thursday, February 17, 2022 6:31 AM > *To:* [email protected] > *Subject:* [M100] Model 200 with LCD all black from power on > > > > Hi everyone, > > > > Gilles here (male name in France). > > > > I have a model 200 which shows an all black LCD screen. > > > > I replaced the battery and fully charged it, no change. > > > > I checked the voltage at the battery when the model 200 is unplugged and > it’s about 3.4-3.5v. > > > > I can hear a click noise in the speaker when I switch the 200 on and also > when I press the reset button. > > > > But, appart from that, nothing seems to occur. > > > > I checked the CPU clock and it is fine. > > > > I also checked the buses and nothing seems stuck. > > > > Power supply for all the chips seems to be correct. > > > > On the LCD connector, I also have some AC voltages of various frequencies. > > > > On very rare occasions (2-3 times not in a raw), the M200 LCD screen is > greyish and the contrast pot adjustment seems to work. > > > > But when the M200 is black from the start, the contrast pot does nothing. > > > > I disconnected and reconnected both the keyboard and the LCD flex cables > without any change and the symptoms. > > > > I don’t see any traces of corrosion nor breakage on the PCBs. > > > > There is no option ROM inserted in the memory board and if I put the > switch on the OFF position, the LCD screen does nothing and I also hear no > click noise in the speaker. > > If I switch it ON, the LCD goes black again. > > > > I’ve read the mails related to the same symptoms and used them to check > things here and there but, well, no joy ! > > > > I have a multimeter and an oscilloscope but don’t know what else I could > check. > > > > Any suggestions ? > > > > Thanks in advance for your help ! > > > > > > Gilles >
