14 Oct
2005
14 Oct
'05
3:50 p.m.
On 10/15/05, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Have yopu tired powering up (or pressing reset) while
holding down the
Break key? A Model 1/3/4 fitted with a disk controller will normally try
to boot from drive 0, but if you hold down Break, it'll go into ROM
BASIC. You should get a CASS? prompt (hit enter), then MEMORY SIZE (enter
again), then get the BASIC sign-on.
I did not try that - I knew there was some reset/key combo but had
forgotten what key to hit. But I'll try that as soon as I'm in front
of the machine again (I'm not home right now).
The Mofrl 3 is actually quite easy to work on. If you
pull the cover, the
monitor section comes off with the cover (be careful not to break the CRT
neck when removing or refitting that cover!),
Heh... I've worked on Classic Macs... had that lesson already. :-(
The CPU board stabds vertically at the back, possibnly
covered withe a
metal shield. Remove that, and you're looking at the component side of
the PCB. The model 3 is mostly TTL, with some RAM (4116 DRAMs, 2114 SRAMs
for the video), ROMs, and a Z80.
Right... I did find GIF schematics and pored over them last night. I
remembered correctly that there's not anything truely bizarre going on
in there - worst case, I can trace faults down to individual chips,
then as part of the replacement process, remove them intact and test
them in an external hand-held IC tester for final confirmation of the
fault. It's easier to clip leads and extract single pins, but I am
good at removing chips without damage.
-ethan