486 case LED display jumpers

Teo Zenios 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:
> http://vogons.zetafleet.com/viewtopic.php?t=10780&sid=f80bc89c785100a9d5bfa236f7e45b31
>
> 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 
> this:
>
> 1 2 3
>   4
>
> 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".
>
> -- 
> Phil.
> classiccmp at philpem.me.uk
> http://www.philpem.me.uk/ 




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