13 Jul
2007
13 Jul
'07
8:11 p.m.
1) Remove the main board from the case, detaching it
from the
front panel board.
2) Remove (carefully noting their positions) all of the ICs
from the main board.
3) Attach dummy loads (24V light bulbs) to the PS at convenient
locations. How many should I use?
4) Attach to AC power in this state. Assuming nothing pops,
check DC voltage (voltages?) with a scope. Assuming DC
looks good, allow to warm up for a few hours.
5) Scope check DC again. Power down allow to cool for a few
minutes. Repeat steps 4 and 5 a few times (3? 4?).
6) If all looks good, reinstall all of the "easy to replace"
ICs and do 4 and 5 again.
7) If all looks good, reinstall the rest of the ICs, restore
the main board to the case and front panel.
8) Debug any logic problems (dead chips, opens, etc.).
Does this look reasonable?
It depends how much free time you have. I would just remove the socketed
parts - ROM, processor, and ACIA. Even with a nice desoldering pump its
likely that a few solder pads will be damaged in the process.
A compromise might be to throw a handful of zener diodes on the main
regulated power rails? +5v, + and -16v, etc. Turn on for a second and see
if they are hot. : )
Assuming you toasted the entire computer I could sell you every single IC
for $50.
Just a pointer, when the Altair 680 is working *properly* the heatsinks
(especially the upside down one) are hot/burn to the touch. Same thing
with the 2W resistor.
You might want to replace the fuse with a new one. Those old ones blow
under proper loads.
I have schematics for this computer if you need them.
Grant