>What puzzles me is why the IMSAI folks decided to use a switching power
>supply when the box and everything else already supported the needs of the
>S-100 with the previously available and now quite inexpensive unregulated
>supplies of yesteryear.
Probably an issue of economy, using PC-clone power supplies at about
$25 each vs using a custom-wound transformer at $200 or so a pop.
> One of the main benefits of the S-100 was that it
>had on-board regulation, so that if you didn't need a given supply, you
>didn't have to bring it on board and regulate it, dissipating power as you
>went. If the new box is capable of running the original boards, it must
>provide the raw 8 and +/- 16-volt supplies. Where's the benefit in having a
>switching regulator sitting in the back of the box? I suppose it creates a
>market for a power distribution module to put +5 and +/- 12 on each board
>which needs it rather than using the on-board regulators, but that opens
>another can of worms. What's the "right" way to distribute it without
>tampering with a historically correct board?
According to what I read from the web page, there's a PC-clone switching
power supply followed by a "boost" switching circuit to get back to
+8 and +/- 16. That's not completely unreasonable, but it sounds a
little bit fishy to me in the sketchiness of the details.
Several S-100 manufacturers who were still at it in the mid-80's had
regulated +5V on the S-100 backplane. Those who wanted to use their
older S-100 cards in such a machine just jumpered across the 7805's and
viola!
--
Tim Shoppa Email: shoppa_at_trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
Received on Tue Aug 17 1999 - 17:22:02 BST