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
modules are soldered in place and I would like to troubleshoot the board to
avoid unnecessary removal of parts. If anyone has other troubleshooting steps,
I'm happy to try them out. I have access to a logic analyzer (Saleae
software), oscilloscope, and DMM.
Issue: When powered up, LCD shows pixels only (black screen w/adjustable
contrast)
Troubleshooting Performed: New NiCad installed and charged (memory switch
on). Board traces near battery corrosion have good continuity. All
capacitors were replaced. Board traces near leaking capacitors have good
continuity. Cold Start and "BEEP" attempted. Beep was not heard. DC/DC
Converter Circuit meets specs per section V of Service Manual 26-3801/3802
Reset Signal meets specs per section V of Service Manual 26-3801/3802 Logic
Circuit meets specs per section V of Service Manual 26-3801/3802 CPU, ROM,
Ram all have activity on the scope. Clock signal looks acceptable.
Eric
