13 Jul
2007
13 Jul
'07
3:30 p.m.
I've just been given access to an Altair 680. It seems to be
in excellent physical condition (no rust, corrosion, dents...
just some dust). Has not seen power in many years. All of
the ICs are socketed. Due to the fact that the PS is
incorporated onto the main board, I was planning the following:
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?
Thanks,
Bill
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4:08 PM
13 Jul
13 Jul
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
8:37 p.m.
Grant Stockly wrote:
It depends how much free time you have. I would just
remove the socketed
parts - ROM, processor, and ACIA.
All of the ICs are socketed in this 680.
Assuming you toasted the entire computer I could sell
you every single IC
for $50.
I might take you up on that...
I was wondering about getting a copy of VTL-2 in ROM/EPROM.
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.
That's good to know.
You might want to replace the fuse with a new one.
Those old ones blow
under proper loads.
Good to know as well.
I have schematics for this computer if you need them.
Yes, definately. Thanks!
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.476 / Virus Database: 269.10.4/898 - Release Date: 7/12/2007
4:08 PM
9:33 p.m.
At 04:37 PM 7/13/2007, you wrote:
The ACIA is normal temperature, the 6800 gets kind of warm (do you have a
ceramic one?), and the 1702 can get pretty warm. This is based on the
surronding ICs.
I've learned a lot about debugging Altair 680s. I've repaired 1, and built
2 more from scratch in the last few months. : ) Its a pretty easy
computer to work with. I like it.
Grant
Grant Stockly wrote:
Oh, in that case, go for taking them all out if you want. In the two 680s
I've worked with everything but the ROM, processor, and 6850 was soldered
to the PCB! : )
It depends how much free time you have. I would
just remove the socketed
parts - ROM, processor, and ACIA.
All of the ICs are socketed in this 680. I was wondering about getting a copy of VTL-2 in
ROM/EPROM.
$30 + shipping, or less if you want to mail me 3 good 1702s.
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.
That's good to know. 
14 Jul
14 Jul
5:29 a.m.
On Fri, 2007-07-13 at 15:30 -0400, Bill Sudbrink wrote:
I've just been given access to an Altair 680. It
seems to be
in excellent physical condition (no rust, corrosion, dents...
just some dust). Has not seen power in many years. All of
the ICs are socketed. Due to the fact that the PS is
incorporated onto the main board, I was planning the following:
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?
Wouldn't it be easier to just remove the voltage regulators from the PCB
and test them, and test the unregulated PSU outputs?
That way you can be reasonably confident that when you put the PSU back
together it will be safe, without the attendant risks of screwing up the
rest of the machine.
Gordon
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4 comments
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gordon＠gjcp.net -
grant＠stockly.com -
wh.sudbrink＠verizon.net