Re: [M100] Non working display on my m100
Another one fights the dust! -- bkw On Wed, Jul 10, 2019, 12:06 AM George Hines wrote: > Thanks for all the information and advice. > > I'm happy to report one more m100 is working. > > Two of the caps I had replaced c82 and c85 had leaked, damaging the > circuit board on top. I didn't notice it during my recap, lesson learned > to look more carefully next time. > > Underneath c82 was a small trace that runs to the contrast control. Once > I cleaned up the leak damage and patched the trace, the screen came back to > life. > > I chased down some dead ends while debugging, but learned a bunch in the > process. > > That was kind of fun! >
Re: [M100] Non working display on my m100
*"That was kind of fun!"* Good way to express it! Tom M. On Wed, Jul 10, 2019 at 12:06 AM George Hines wrote: > Thanks for all the information and advice. > > I'm happy to report one more m100 is working. > > Two of the caps I had replaced c82 and c85 had leaked, damaging the > circuit board on top. I didn't notice it during my recap, lesson learned > to look more carefully next time. > > Underneath c82 was a small trace that runs to the contrast control. Once > I cleaned up the leak damage and patched the trace, the screen came back to > life. > > I chased down some dead ends while debugging, but learned a bunch in the > process. > > That was kind of fun! >
Re: [M100] Non working display on my m100
On my M100 with no screen attached the V2 voltage ranges from about 1.5V to almost 3V. From: M100 mailto:m100-boun...@lists.bitchin100.com>> on behalf of George Hines mailto:mrthreepla...@gmail.com>> Reply-To: mailto:m...@bitchin100.com>> Date: Saturday, July 6, 2019 at 3:48 PM To: mailto:m100@lists.bitchin100.com>> Subject: [M100] Non working display on my m100 Thanks for the suggestions and tips! I've checked c105 and c106 and they are close to their speced values. I checked the variable resistor and it seems to be okay. I'll recheck the v2 range again, it does seem like it should have a greater range.
Re: [M100] Non working display on my m100
The contrast voltage appears to be too low if memory serves the voltage swing needs to be greater than 300mV, the manual indicates the swing should be around 4V (pg 38). It could be that VR1 needs cleaning or at least checking out or c106/c105 might have problems. The display sounds like it is working just the contrast voltage is too low. If the display were dead the BASIC BEEP command would not work – the boot sequence checks the display and hangs if it does not read back correctly. From: M100 mailto:m100-boun...@lists.bitchin100.com>> on behalf of George Hines mailto:mrthreepla...@gmail.com>> Reply-To: mailto:m...@bitchin100.com>> Date: Friday, July 5, 2019 at 10:15 AM To: mailto:m100@lists.bitchin100.com>> Subject: [M100] Non working display on my m100 I checked v2 at the interface and it varies from 1.4 to 1.7 volts as I adjust the contrast.
Re: [M100] Non working display on my m100
It might be the contrast dial. I have an NEC unit that goes blank until I turn it all the way up. You should be able to check that with a multi-meter. Could be the actual screen though. Kurt On Fri, Jul 5, 2019, at 10:34 AM, George Hines wrote: > Sorry I should have added: > > Ther screen wasn't working before I started the recapping and battery > replacement, so I don't think I made it any worse. > > And to be clear, I can't get any response from the screen at all no matter > what I do: No flickering or darkening or flashes. > > Thanks in advance for any advice! > > Best regards.
