RE: [N8VEM-S100:1000] S-100 backplane request for help

["John Monahan" <mon...@vitasoft.org>]

Paul, 12A on the 7.5V may be a little on the low side unless you are just
sticking to 8 bits.  The 16 bit CPU boards have 3A regulators and if you
have a dual (or more) CPU master slave setup, things could get tight. Agree
20A's is probably best. The 16 V lines are really only used for RS232 etc.
these days and even there, there are converter chips. So 1-2 A is fine.

John



John Monahan Ph.D
e-mail: mon...@vitasoft.org
Text:    mon...@txt.att.net


-----Original Message-----
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On
Behalf Of Paul Birkel
Sent: Sunday, July 22, 2012 11:37 AM
To: n8vem...@googlegroups.com
Subject: Re: [N8VEM-S100:1000] S-100 backplane request for help

While John has some great information on his backplane/ps page
(http://s100computers.com/My%20System%20Pages/The%20Box/The%20Box.htm#The_Po
wer_Supply),
one point that is missing is the proper power supply sizing for an 8-slot
system.

The IEEE 696:1983 spec is silent on the allowed/anticipated ps-loading per
slot, but it seems reasonable to assume 1 A to maybe 1.5 A average per slot
on the 8V rail, max (most cards hosting a single 1A +5V regulator, with the
occasional dual-regulator configuration like the dual-IDE card)?  That
suggests maybe 12A on the 8V rail, and we might guess 1-2A max on the +16
and -16V rails (since these aren't used much at all on modern cards)?

Am I way off-base here?

FWIW, here are what appear to be the most relevant Meanwell supplies (via
Power Factor, as pointed out by John) -- all of which can have their output
voltages adjusted upwards a bit to fit the 8 and 16 volt
bus-targets:

http://www.power-factor-1st.com/g2-series/s-100f.html 7.5V, 0~13.5A  $49.45
http://www.power-factor-1st.com/g2-series/s-150.html  7.5V, 0~20A  $55.45
http://www.power-factor-1st.com/g2-series/s-210.html  7.5V, 0~27A  $70.95
http://www.power-factor-1st.com/g2-series/s-40.html    15V, 0~2.8A  $37.90

The 20A (second line) seems to be the cost-effective sweet-spot "with
headroom".

Happy hunting :->.

On Sun, Jul 22, 2012 at 1:55 PM, Andrew Lynch <LYN...@yahoo.com> wrote:
> Hi!  I?ve gotten a request for some help with the S-100 backplane PCB.
> Since it will probably require a PCB respin to fix I would like to 
> gather up all the feedback and incorporate them as best I can.  Thanks 
> to Don Caprio there are some excellent builder instructions here:
>
> http://n8vem-sbc.pbworks.com/w/page/35158565/Build%20Instructions
>
> Please post photos of your completed working S-100 backplane systems 
> on the wiki in the S-100 backplane folder. Actual builder photos are 
> *very* helpful for new builders.
>
> http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder&param=S-100%20b
> ackplane
>
> There is a new file for S-100 backplane fixes and improvements here:
>
> http://n8vem-sbc.pbworks.com/w/page/55620344/S-100%20backplane%20impro
> vements%20and%20fixes
>
> Please edit with any issues you?ve encountered on how to fix and/or 
> improve the S-100 backplane.
>
> The photos that are in the folder at the moment are getting rather 
> dated so they should be retired to the archive as to not confuse any new
builders.
>
> Thanks and have a nice day!
>
> Andrew Lynch