17 Oct
2008
17 Oct
'08
10:15 a.m.
I have most of the stuff to put together a System 3. I have the card cage with the
21-slot motherboard and a bunch of cards. The manuals I got with the system include the
Cromix manual, I have more than 1 64-K RAM card and at least one TPU, so I believe that
mine was a multi-user system. I would like to put this back to near-original, but need a
case and power supply.
Since I have been unable to find any power supplies which provide the +/- 8 and +/- 16
volts, I just thought of an idea the other day of using a PC power supply and shorting out
the on-board voltage regulators to allow them to work at the +5V and +12V of the power
supply. In order to do that though, I would need a small (3-5 slot) motherboard to test a
couple of cards together.
If anyone has any of these available, I would be interested in obtaining them. I do not
have much money, but do have some other old computer stuff that I can trade: a VAX Station
2000, an old Sun workstation, many, many old PC parts and systems, lots of electronic
parts, lots of microcontroller stuff including several Dev Kits.
Also if anyone has done this before please let me know how it went.
Thanks,
Art
17 Oct
17 Oct
12:21 p.m.
On Oct 17, 2008, at 10:15 AM, Granz wrote:
I have most of the stuff to put together a System 3.
I have the
card cage with the 21-slot motherboard and a bunch of cards. The
manuals I got with the system include the Cromix manual, I have
more than 1 64-K RAM card and at least one TPU, so I believe that
mine was a multi-user system. I would like to put this back to
near-original, but need a case and power supply.
Since I have been unable to find any power supplies which provide
the +/- 8 and +/- 16 volts, I just thought of an idea the other day
of using a PC power supply and shorting out the on-board voltage
regulators to allow them to work at the +5V and +12V of the power
supply. In order to do that though, I would need a small (3-5
slot) motherboard to test a couple of cards together.
I don't think it's going to be possible to short around the +5 and
+12 regulators in a PC power supply, as they're not discrete in that
way. Your best bet (IMO) is to surf eBay for an big open-frame
linear power supply. These are usually based on LM723 voltage
regulators and 2N3055 (or similar) pass transistors, and it's easy to
bridge around that sort of regulator. Otherwise you can just tweak
the voltage upward to the 8/16 that you want using the adjustment
variable resistor that's usually present in such power supplies.
If anyone has any of these available, I would be
interested in
obtaining them.
Sadly I do not, but...
I do not have much money, but do have some other old
computer
stuff that I can trade: a VAX Station 2000, an old Sun workstation,
many, many old PC parts and systems, lots of electronic parts,
What model of Sun?
lots of microcontroller stuff including several Dev
Kits.
I'm definitely interested in that stuff, if I have anything else
you may be looking for. What sort of microcontrollers and dev kits?
-Dave
--
Dave McGuire
Port Charlotte, FL
9:01 p.m.
On 17 Oct 2008 at 12:21, Dave McGuire wrote:
Brute-force linear is definitely the way to go.
I'd be tempted to grab a couple of filament transformers, a couple of
bridge rectifiers and some big caps. The great thing about S100
power supplies is that PSU regulation isn't important. A 6.3VAC
filament transformer hooked through a bridge rectifier and a big
electrolytic should be close enough. +/-16 could be furnished by a
small 12.6v transformer.
The real job of regulation is furnished on each board (usually
something like 78xx 79xx linear regulator ICs).
Cheers,
Chuck
Since I have
been unable to find any power supplies which provide
the +/- 8 and +/- 16 volts, I just thought of an idea the other day
of using a PC power supply and shorting out the on-board voltage
regulators to allow them to work at the +5V and +12V of the power
supply. In order to do that though, I would need a small (3-5
slot) motherboard to test a couple of cards together.
I don't think it's going to be possible to short around the +5 and
+12 regulators in a PC power supply, as they're not discrete in that
way. Your best bet (IMO) is to surf eBay for an big open-frame
linear power supply. 
19 Oct
19 Oct
1:29 a.m.
On Friday 17 October 2008 12:21, Dave McGuire wrote:
On Oct 17, 2008, at 10:15 AM, Granz wrote:
I don't think that's what he was talking about there. I remember some S-100
cards coming with regulators (all of them did, early on), and later the
input and output points where those regulators _had been_ were connected with
a wire jumper in the assumption that a switching power supply of some sort
with regulated outputs would be used instead of the original S-100
unregulated supply.
The catch, though, is that the System 3 needs a +24V supply as well, for
the FDD. I have one, and it uses an oddball connector, too, which is one
of the reasons I haven't gotten around to fixing the drive yet (which has
problems), I need to make an extension power cable for the drive so it can
be powered up and out in front of the case.
(Snip)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
I have most of the stuff to put together a System
3. I have the
card cage with the 21-slot motherboard and a bunch of cards. The
manuals I got with the system include the Cromix manual, I have
more than 1 64-K RAM card and at least one TPU, so I believe that
mine was a multi-user system. I would like to put this back to
near-original, but need a case and power supply.
Since I have been unable to find any power supplies which provide
the +/- 8 and +/- 16 volts, I just thought of an idea the other day
of using a PC power supply and shorting out the on-board voltage
regulators to allow them to work at the +5V and +12V of the power
supply. In order to do that though, I would need a small (3-5
slot) motherboard to test a couple of cards together.
I don't think it's going to be possible to short around the +5 and
+12 regulators in a PC power supply, as they're not discrete in that
way. 
18 Oct
18 Oct
3:01 a.m.
On Fri, 17 Oct 2008, Granz wrote:
I have most of the stuff to put together a System 3.
I have the card
cage with the 21-slot motherboard and a bunch of cards. The manuals I
got with the system include the Cromix manual, I have more than 1 64-K
RAM card and at least one TPU, so I believe that mine was a multi-user
system. I would like to put this back to near-original, but need a case
and power supply.
Since I have been unable to find any power supplies which provide the
+/- 8 and +/- 16 volts, I just thought of an idea the other day of using
a PC power supply and shorting out the on-board voltage regulators to
allow them to work at the +5V and +12V of the power supply. In order to
do that though, I would need a small (3-5 slot) motherboard to test a
couple of cards together.
If anyone has any of these available, I would be interested in obtaining
them. I do not have much money, but do have some other old computer
stuff that I can trade: a VAX Station 2000, an old Sun workstation,
many, many old PC parts and systems, lots of electronic parts, lots of
microcontroller stuff including several Dev Kits.
Are you set on having a System 3 chassis for this? I think I have at
least one more 21-slot chassis, the name of which I'm not at all sure of.
--
David Griffith
dgriffi at cs.csubak.edu
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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cclist＠sydex.com -
dgriffi＠cs.csubak.edu -
granz_consult＠hotmail.com -
mcguire＠neurotica.com -
rtellason＠verizon.net