This is turning out to be "fun". The screen used to not do anything but after replacing my patch wire the screen is still blank (don't think it's black, only turns grayish when I push the contrast up all the way) but I'm able to manipulate the contrast and I'm no longer able to make the computer beep. I'm not really equipped to measure negative voltage (only have an analog meter), but VDD measures 5V and VEE makes the meter's needle go as left as possible, when before the patch wire it measured around +0.2 volts.
-Nathan On Sat, Jul 21, 2018 at 6:06 PM, Jeffrey Birt <[email protected]> wrote: > When you turn on the M100 does the screen come on all black? The way the > LCD controllers work is that they will turn ‘ON” every LCD segment upon > power up. When the M100 boots it will send a ‘clear’ signal to the LCD > controllers. If you don’t see the solid black screen it is an indication of > a power supply issue. > > > > As Fugu said check the -5V, +5V to the LCD I would check on the LCD side > of the connector first. If you don’t have both supplies, then trace it back > to the source. > > > > Jeff > > > > *From:* M100 <[email protected]> *On Behalf Of *Fugu ME100 > *Sent:* Saturday, July 21, 2018 4:31 PM > *To:* [email protected] > *Subject:* Re: [M100] Model 100 LCD doesn't work > > > > You may have already checked but make sure the –5V is good and that the > contrast pot is working sometimes they do not work so the screen is in low > contrast mode = not visible but still working. You should be able to see > the screen go almost entirely black as you turn the contrast pot or the > menu might appear :) > > > > Buzz out all the connections to the LCD header make sure no other trace > has been damaged by a capacitor leak, it is possible to miss a break. > Make sure the connection onto the LCD is good and no corrosion has happened > due to capacitors out gassing. I have had a trace corrode under one of > the caps that caused the screen to stop working. > > > > The fact it beeps is a good sign it means the keyboard interface seems to > be working, some of the same chips drive the LCD so they are probably good. > > > >
