Re: S-100 Power supplies and Alternatives
- From: no.spam@xxxxxxxxxxxxxxxxxxxxxxx
- Date: Tue, 02 Oct 2007 15:05:27 GMT
On Tue, 02 Oct 2007 06:51:17 -0000, Grant Stockly <grant@xxxxxxxxxxx>
wrote:
On Oct 1, 8:21 am, amou...@xxxxxxxxx wrote:
A sad tale with a question ....
Question: What do people use for replacement S100 S-100 power
supplies ...?
I have fully decked the Altair with 8k SEALS cards... With this route
you could leave your cards alone. I banged my head into a wall trying
to maintain the cards original design while still having switchers...
Not going to succeed unless you either mod a PC switcher (involved)
or find something out there ($$$). The simple S100 PS is far too
simple to not fix.
Where a switcher is handy in the S100 world is for powering disks.
Some systems, NS* Horizon come to mind have regulators
for running the disk drives and they will not run a hard disk as
they were intended for SA400 class floppies. There a seperate
50W +5 and +12 switcher is a useful item for running hard disks
especially those older 5.25 full height types that sucked up around
30W.
Generally if power was suppled for Drive is was off seperate
regulation from the baords even though the raw DC may have
come from the same source.
A few of the fancier S100crates like the Compupro and Intergrand
added a constant voltage transformer in place of the usual large
iron and that tended to keep the +8/+16/-16 a more like 10%
regulated and also helped with brownouts.
Some people ask me if 100w/60w is enough. Power Factor has bigger
supplies if it is a concern. The switchers will supply their output
with a lot less voltage drop than a linear supply. I wonder if a lot
of the linear supplies were over done because of that...
This is not true. I have linears that have less noise and droop than
any switcher. Power One was a common source of those. However,
_ most_ S100 system didn't use linear supplies for the bus DC, they
put raw rectified and filtered DC and the cards handled regulation
locally using 7805, LM309, LM323 type three terminal regulators.
FYI: droop is not related to type of supply but the leads and traces
from the PS to the load (boards) and the only way to nullify that is
to use remote sensing that most better linear and switch mode PS
offer. This is also referred to as a four wire power, where two heavy
leads supply DC and the two fairly light leads connect the load at
point of use back to the regulator circuits.
However the average S100 +8 bus was rated for 25 Amps and that
would be 200W output (for a 8V switcher). You also have the +16
that was usually good for at least 3A (48W at 16V) and the -18 was
often lightly loaded at under 1A (16W at 16V).
They are trimmed up from 7.5v and +/-15v. Look at http://www.power-factor-1st.com/
Yes, some switchers will tweek up to those but watch as some also have
over voltage fault sensing and shut down. Also 7.5V is marginal for
most three terminal regulators. It will work but.. you have no
margin. I'd use four wire hookup (remote sense) for the 7.5V
if you do that to help matters.
It's possible to mod a PC swicher for any voltage out but it's not for
the novice. FYI: switchers have HV inside!
Allison
S-100F
T-60
Grant
.
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