486 case LED display jumpers

M H Stein dm561 at torfree.net
Wed May 27 22:25:51 CDT 2009

-------------Original Message:
Date: Wed, 27 May 2009 14:28:41 -0400
From: "Teo Zenios" <teoz at neo.rr.com>
Subject: 486 case LED display jumpers

>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.

I do, but it's such poor quality that a scan would be illegible.

Oriented with the four pin connector at top right:

The four pins are: +5, Gnd, Turbo LED, NC

The three pins are the turbo switch: Low, common, High.

The bottom row of 28 is the tens digit, and the one above it the units. 
Optionally there may be another four for a hundreds "1" digit which you
apparently don't have.

Segments are a-g left to right, and each segment is controlled by four 
pins arranged in a 'T', alternately upside-down and right-side-up.

 a       b      c
 x     xxx     x
xxx    x     xxx   etc. (spread apart for clarity)

The junction of the three "bars" goes to the segment, and the three end 
points are the power source:

Looking at each "T" in its proper orientation:
Jumper down the leg = always on. 
Jumper on the left bar = on with turbo
Jumper on right bar = on with normal

Segments are named the usual way, a-f clockwise with a on top, g in the centre.

Clear as mud?

Hope it helps; almost as much fun as figuring it out yourself...


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