Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!lll-winken!sun-barr!newstop!texsun!letni!merch!rwsys!jim
From: jim@rwsys.lonestar.org (James Wyatt KA5VJL                .)
Newsgroups: comp.sys.tandy
Subject: Re: Modem for an HX
Summary: The HX power supply is too anemic for much expansion
Keywords: expansion smoke
Message-ID: <438@rwsys.lonestar.org>
Date: 13 Aug 90 04:23:16 GMT
References: <7220@helios.TAMU.EDU> <193300223@trsvax>
Reply-To: jim@rwsys.UUCP (James Wyatt KA5VJL)
Distribution: na
Organization: R/W Systems, Irving Texas, 75060-6055
Lines: 27

In article <193300223@trsvax> reyn@trsvax.UUCP (Juan Reynolds) writes:
>The "expansion" bus of the hx is "compatible" with the ISA XT bus except
>for the conector.  It would be a real kludge, but you could wire a mating
>connector to the hx slot to a "standard" card edge connector.

The HX's power supply was designed to support only the internals of the HX
and a small amount of expansion. The only hard disk interface I have heard
of used the disk drive's power supply, rather than tax the HX. Most modems
don't draw much power, but other expansion cards (EMS, some network cards,
etc...) thirst for power. Before you try adding something to the HX, check
how much power it uses and, if possible, add an external power supply (+5V)
which shares only ground with the HX. Most network cards need +12V, serial
port cards need -12V and +12V. See the manual or ask the manufacturer.

If you use a ribbon cable with a PC edge socket and a header on it for your
expansion board, keep the cable as short as is practical. As the cable length
grows, the timing skew, induced noise, and neighborhood television problems
get much worse.

The HX is a decent machine to test prototype boards. It sure is better than
risking your 2/3/486 to a 1 a.m. bad solder joint across something important.
At least it has a 3.5 drive and works with a TV. I wonder if it could use one
of the old IBM PC expansion kits... 8{)
----
James Wyatt (KA5VJL) - Standard disclaimer applies...          (H)214-579-0425
                           {letni.lawnet.com}!rwsys.lonestar.org!jim
{sys1.tandy.com!sneaky.UUCP,merch.tandy.com}!/                 (W)817-390-2864