28 Feb
2009
28 Feb
'09
10:03 a.m.
Hi! What are acceptable voltage supply ranges for an S-100 power supply? I
am assuming 115VAC input. My intended application is a small home brew
S-100 backplane.
I have seen the S-100 voltage rails vary but I believe +15VDC, -15VDC, and
+9VDC would be sufficient. Herb's S-100 page lists the voltages as +18VDC,
-16VDC, and +8VDC but I have seen other voltages used.
Thanks and have a nice day!
Andrew Lynch
28 Feb
28 Feb
10:12 a.m.
On 2/28/09 10:03 AM, "Andrew Lynch" <lynchaj at yahoo.com> wrote:
Hi! What are acceptable voltage supply ranges for an
S-100 power supply? I
am assuming 115VAC input. My intended application is a small home brew
S-100 backplane.
I have seen the S-100 voltage rails vary but I believe +15VDC, -15VDC, and
+9VDC would be sufficient. Herb's S-100 page lists the voltages as +18VDC,
-16VDC, and +8VDC but I have seen other voltages used.
Most of the S-100 cards used on-board linear regulators so I'm sure that the
filtered DC voltages on those rails were set to provide adequate input
headroom for the 7805's and 7812's that were typically used.
Of course there may be exceptions.
Rich
--
Rich Cini
Collector of Classic Computers
Build Master and lead engineer, Altair32 Emulator
http://www.altair32.com
http://www.classiccmp.org/cini
10:37 a.m.
Rich is right.
No commodity LDO regulators to be had then.
Suplies to rail were usually big transformer and bridge rectifier in
front of large caps.
American iron was inexpensive then.
Steve
Richard A. Cini wrote:
On 2/28/09 10:03 AM, "Andrew Lynch"
<lynchaj at yahoo.com> wrote:
Hi! What are acceptable voltage supply ranges
for an S-100 power supply? I
am assuming 115VAC input. My intended application is a small home brew
S-100 backplane.
I have seen the S-100 voltage rails vary but I believe +15VDC, -15VDC, and
+9VDC would be sufficient. Herb's S-100 page lists the voltages as +18VDC,
-16VDC, and +8VDC but I have seen other voltages used.
Most of the S-100 cards used on-board linear regulators so I'm sure that the
filtered DC voltages on those rails were set to provide adequate input
headroom for the 7805's and 7812's that were typically used.
Of course there may be exceptions.
Rich
--
Rich Cini
Collector of Classic Computers
Build Master and lead engineer, Altair32 Emulator
http://www.altair32.com
http://www.classiccmp.org/cini
11:13 a.m.
Hi
Look at the minimum level of the ripple. Most linear
regulators specify 3volts of head room. Add a little for
trace drop.
If regulated lines, I'd suspect that 15v for a 12v line is enough.
If simply filtered, you'll need heavy filters or you'll drop below
the 3v line.
Dwight
From: lynchaj at yahoo.com
To: cctalk at classiccmp.org
Date: Sat, 28 Feb 2009 10:03:10 -0500
Subject: S-100 power supply voltage ranges
Hi! What are acceptable voltage supply ranges for an S-100 power supply? I
am assuming 115VAC input. My intended application is a small home brew
S-100 backplane.
I have seen the S-100 voltage rails vary but I believe +15VDC, -15VDC, and
+9VDC would be sufficient. Herb's S-100 page lists the voltages as +18VDC,
-16VDC, and +8VDC but I have seen other voltages used.
Thanks and have a nice day!
Andrew Lynch
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Windows Live?: Life without walls.
http://windowslive.com/explore?ocid=TXT_TAGLM_WL_allup_1a_explore_032009
11:49 a.m.
All of the S100 boards I've seen use simple linear regulators, so you
need some headroom--but not too much. A lot of S100 7805s and LM323-
5s were operated within an inch of their maximum current ratings
(some had bypass resistors installed) and generated a lot of heat. I
wouldn't run the supply rails any higher than I had to.
Cheers,
Chuck
12:07 p.m.
Chuck Guzis wrote:
All of the S100 boards I've seen use simple linear
regulators, so you
need some headroom--but not too much. A lot of S100 7805s and LM323-
5s were operated within an inch of their maximum current ratings
(some had bypass resistors installed) and generated a lot of heat. I
wouldn't run the supply rails any higher than I had to.
Cheers,
Chuck
The Sol-20 had an app note about this problem. Apparently they shipped
them for a while with transformers that were out of spec with the end
result that the unregulated power ran high. The recommended fix was to
take a power bridge, mount it to the case, and wire it in series with
the positive voltage run in order to get a ~1.4V drop.
2 Mar
2 Mar
2:42 a.m.
On Feb 28, 2009, at 10:03 AM, Andrew Lynch wrote:
Hi! What are acceptable voltage supply ranges for an
S-100 power
supply? I
am assuming 115VAC input. My intended application is a small home
brew
S-100 backplane.
I have seen the S-100 voltage rails vary but I believe +15VDC,
-15VDC, and
+9VDC would be sufficient. Herb's S-100 page lists the voltages as
+18VDC,
-16VDC, and +8VDC but I have seen other voltages used.
Every S-100 chassis I've seen has +/- 16VDC and +8VDC power
supplies, and most of them are unregulated due to distributed
regulation (7805s, 7812/7912 if needed) on each board.
-Dave
--
Dave McGuire
Port Charlotte, FL
2 p.m.
Andrew Lynch wrote:
Hi! What are acceptable voltage supply ranges for an
S-100 power supply? I
am assuming 115VAC input. My intended application is a small home brew
S-100 backplane.
I have seen the S-100 voltage rails vary but I believe +15VDC, -15VDC, and
+9VDC would be sufficient. Herb's S-100 page lists the voltages as +18VDC,
-16VDC, and +8VDC but I have seen other voltages used.
Thanks and have a nice day!
Andrew Lynch
While I do not know all the ranges of voltages folks here are dealing
with on many classic computers I can assure everyone that putting in
devices called "Tranzorbs/Transorbs" for machines running with Linear
Power Supplies (not as required for switching supplies) may protect your
computer from problems with linear power supplies that do not have
output voltage protection.
In the old days the manufacturers often used devices called "Crowbars"
that would literally short out the outputs of the supply if the output
voltage rose past a predefined point. This would protect the downstream
components from most power supply issues.
Lots of folks here are in areas with less than perfectly regulated mains
and Transorbs can also smooth down momentary surges.
Transorbs can be found with many suppliers and they can easily be added
to most power supplies - if you are concerned that the Transorb will
burn out (perhaps those 100A 5VDC rails) then you can put a few in and a
fuse between the supply and the Transorb (and load). The fuse should
blow before the Transorb explodes...
MOVs on the line input can protect your devices from lightning strikes,
etc. and are contained in good quality surge suppression protection
extension cords or UPS supplies.
John :-#)#
--
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
www.flippers.com
"Old pinballers never die, they just flip out"
3 Mar
3 Mar
8:56 p.m.
From: jrr at flippers.com
While I do not know all the ranges of voltages folks here are dealing
with on many classic computers I can assure everyone that putting in
devices called "Tranzorbs/Transorbs" for machines running with Linear
Power Supplies (not as required for switching supplies) may protect your
computer from problems with linear power supplies that do not have
output voltage protection.
In the old days the manufacturers often used devices called "Crowbars"
that would literally short out the outputs of the supply if the output
voltage rose past a predefined point. This would protect the downstream
components from most power supply issues.
Lots of folks here are in areas with less than perfectly regulated mains
and Transorbs can also smooth down momentary surges.
Transorbs can be found with many suppliers and they can easily be added
to most power supplies - if you are concerned that the Transorb will
burn out (perhaps those 100A 5VDC rails) then you can put a few in and a
fuse between the supply and the Transorb (and load). The fuse should
blow before the Transorb explodes...
MOVs on the line input can protect your devices from lightning strikes,
etc. and are contained in good quality surge suppression protection
extension cords or UPS supplies.
John :-#)#
Hi
If you have multiple transformers on the same switched line
feeding multiple solid state loads you must put something
like a MOV on the input line to protect things. I learned
this the hard way.
Transformer coils can hold quite a bit of energy. If the switch
opens with the maximum current flowing, there will be a voltage
spike. The weakest link in the system must absorb this. In most
cases of a single transformer, the load is usually enough to
take a small surge. With multiple transformers, it will be the weakest
link.
An input capacitor will help but this also increases the rating
of the power switch needed.
Dwight
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cclist＠sydex.com -
dkelvey＠hotmail.com -
frustum＠pacbell.net -
jrr＠flippers.com -
lynchaj＠yahoo.com -
mcguire＠neurotica.com -
rcini＠optonline.net -
steve＠radiorobots.com