Hi Brian ! Thanks for your reply.
I tried CTRL + BREAK (PAUSE) + RESET or POWER but although I hear clicks in the speaker nothing else occurs and no change on the LCD (= still black). I’ll check the reset line in various places and bus activity on the memory PCB tomorrow. Gilles From: Brian White Sent: Thursday, February 17, 2022 7:02 PM To: [email protected] Subject: Re: [M100] Model 200 with LCD all black from power on 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
