Did you check the Vee voltage? It should be close to -5V. What you describe sounds very much like a failing -5V rail. But need to confirm with the Vee measurement. It might be time to replace the capacitors :(
On 7/1/19, 11:17 AM, "M100 on behalf of Jim Anderson" <m100-boun...@lists.bitchin100.com on behalf of jim.ander...@kpu.ca> wrote: >So, I had a VEE problem a while back, and I haven't got around to >replacing the caps on that motherboard yet. I pulled the board from a >parts machine which I'd already cannibalized for its LCD and keyboard, >and swapped it into mine. (Actually, I didn't even bother pulling the >board, I just put the bottom half of the parts machine together with the >top half of 'my' machine.) > >Anyhow. That was fine, for a while, but last week I pulled it out to >show a relative over the holidays, and within seconds of turning the >power switch on the LCD started to fade, as though someone was turning >the contrast knob down. I turned the contrast knob up a bit and got the >display back, but it continued to slowly fade and I continued to chase it >with the contrast knob until I hit the end of travel, then sadly watched >it fade to total blankness. > >The machine still works in the sense that I can turn it on and get a beep >from the BEEP command in BASIC, but the display is totally blank. > >Is this likely to be another (different) bad capacitor on the motherboard >I'm using now, or is this likely to be something on the LCD board itself? > Ie. If I replace the caps on my original motherboard and swap it back >in, am I likely to still have a blank display? > > > > > > > > jim >
