486 case LED display jumpers
teoz at neo.rr.com
Wed May 27 21:11:22 CDT 2009
That link worked out, thanks.
----- Original Message -----
From: "Philip Pemberton" <classiccmp at philpem.me.uk>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Wednesday, May 27, 2009 3:02 PM
Subject: Re: 486 case LED display jumpers
> Teo Zenios wrote:
>> Anybody happen to have the jumper diagram to set a LED 2 digit case speed
>> setting? The PCB has ST-8A on it if that helps.
> There's a reverse-engineered partial circuit on VOGONS:
> If you could put a photo of the PCB on one of those photo-sharing sites
> (say, Photobucket?) and post the URL, I might have the paperwork kicking
> around in one of my folders. "TH99" (Total Hardware, 1999 edition) might
> also be worth a look, copies of that are kicking around on Google.
> Usually the jumpers are laid out in a tesselated "T" pattern, a bit like
> 1 2 3
> Valid jumper positions are 1-2, 2-3, 2-4 or no jumper. If memory serves,
> 1-2 is "on with TURBO on", 2-3 is "on with TURBO off", 2-4 is "on all the
> time", no jumper is, well, segment not lit. Which segment is tied to which
> jumper cluster depends on the specific display in use.
> Of course, you get boards designed by folks who thought they were being
> clever, which end up with a layout like:
> 1 a 3
> b 4 c
> 1 d 3
> (or something like that, I've probably got it at least a little wrong)
> Letters = segments; 1,3,4 = supplies.
> You could probably reverse-engineer one with a multimeter in about 25
> minutes. Remove all the jumpers, Set TURBO off, find all the lines that
> are high, repeat with TURBO on. From that you'll be able to figure out
> which pins are always-high, and which depend on the state of the TURBO
> input. Anything that stays low is a segment. If dealing with a
> common-anode display, reverse "high" and "low".
> classiccmp at philpem.me.uk
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