S-100 Bus Voltages

From: ajp166 <ajp166_at_bellatlantic.net>
Date: Sat Jun 2 21:07:09 2001

From: Edwin P. Groot <epgroot_at_ucdavis.edu>
> After pulling all but one of the cards out I powered up the system.
>Fans run fine, but the motherboard voltage supplies are rather high.
For
>+8V I measure 10.7V; for +16V I get -19.3V; and for -16V I get -19.3V.
Is
>this some careless engineering, bad components, or is the board really
NOT
>supposed to receive the nominal voltage?


Obviously you have no expereince with S100. The Voltages supplied to the
bus
are UNREGUALTED with a minima of +8, +15 and -15. Each card carries
it's own local regulation to resolve the 5/12/-12/-5 as needed.

> Many of the S-100 boards are discoloured brown-green on the solder
>side opposite these large transistor-like things with heat sinks. Is
that
>something to worry about?


Typical and those large transistor like things are voltage regulators.

>Does that look safe enough to put the boards back and see how this
system
>runs?

The measurments you made are mostly meaningless. Is it safe? Likely is
but that done not mean it will run. I'd have to assume the boards in
there
are a complete set and configured (memory and IO addresses correctly set)
for anything good to happen. S100 was NOT plug and play.

> A fair amount of current runs through these slots. I nearly welded
my
>probe to the slot when I accidently shorted two pins!


Obviously contacted +8 to the -16. And yes those supplies are typically
good for 25A on the +8 and 4-8A on the +15.

Allison
Received on Sat Jun 02 2001 - 21:07:09 BST

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