19 Jul
2013
19 Jul
'13
8:26 a.m.
On Jul 19, 2013, at 11:03 AM, Dave <dfnr2 at yahoo.com> wrote:
Hi all,
I have a 9830A that I haven't powered up in a while. Previously, it would take a few
seconds to get to the lazy-T prompt, but now on powerup, the screen remains blank. I got
Tony Duell's phenomenal schematics, and was all set to start debugging, starting at
the clock, but I checked the user manual first, and following the suggestion in the setup
section, I hit "STOP", which brought me to the prompt, and from there, it
appears to be functioning normally. However, the machine powers up this way every
time--never to a prompt.
Does anyone have an idea why the machine is behaving this way? I'd love to have it
power up to a prompt.
I know nothing about the particular machine (or line of machines), but it sounds
like a power-on reset isn't firing. The Apple II (original) didn't have one, and
you had to manually hit the reset key at startup, which sounds similar to this.
That's based on general computing knowledge, though, so I could be ENTIRELY off
base. Might be a good place to start looking, at least. Sometimes those POR
circuits used large electrolytics for large time constants, so if the capacitor
has gone off, it could well be firing too soon, before things have settled.
- Dave