You can check each address line at the ROM to see they are all being twiddled
and that those connections are good. This is not fool proof as a bad bus latch
or any chip on the address bus can much up one of more lines.
The data lines are more complicated. If you test at the ROM you will see
I had a RAM problem with my Model 100 when I first got it. It seemed to work
fine initially, but attempting to paste text resulted in odd characters
appearing, and the amount of free memory slashing drastically.
Various people were very confused as to why this was happening, but a bit of
Thank you everyone for the quick response!
When I power up the computer, all pixels are on and remain dark (LCD is
entirely "black").
Contrast potentiometer: Seems to work as intended. The display will lighten
or darken as the potentiometer is adjusted.
LCD PCB: No signs of corrosion
One thing about the LCD; if the lcd driver write acknowledge signal is
broken, the cpu will be caught in an endless loop waiting for thr drivers
to write successfully.
In this state the cpu would be running but in a software loop polling the
driver write ack signal.
Sounds like a possibility
On Thu, Dec 28, 2023 at 10:35 AM wrote:
> When LCDs with these types of LCD driers first power up they turn on all
> the pixels. You will see this even in brand new ‘modern’ dot matrix LCD
> module (on the new LCDs the multiline modules tend to only make the first
> row black on power up.) Only
When LCDs with these types of LCD driers first power up they turn on all the
pixels. You will see this even in brand new ‘modern’ dot matrix LCD module (on
the new LCDs the multiline modules tend to only make the first row black on
power up.) Only after the computer sends a rest command to the
On Thu, Dec 28, 2023 at 1:13 AM Eric wrote:
> Hi,
>
> I'm working to troubleshoot a non-functional Model 100 that only displays
> pixels when powered up. Seems these computers occasionally have RAM issues
> but I'm not sure how to identify faulty RAM that has not been removed. The
> RAM
Could be a bad contrast potentiometer.
On Thu, Dec 28, 2023, 1:13 AM Eric wrote:
> Hi,
>
> I'm working to troubleshoot a non-functional Model 100 that only displays
> pixels when powered up. Seems these computers occasionally have RAM issues
> but I'm not sure how to identify faulty RAM that
