486 case LED display jumpers

Mr Ian Primus ian_primus at yahoo.com
Wed May 27 14:14:06 CDT 2009

--- On Wed, 5/27/09, Philip Pemberton <classiccmp at philpem.me.uk> wrote:

> 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".

Man, I remember setting these up... but it's been a while. When they were new, of course, the cases came with little diagrams and instructions...

You should be able to figure it out with trial and error, it's really unlikely something could blow up. Just fiddle with jumpers until you get it to say either the speed of the computer, or "HI". Every one I've ever seen was set up like Philip described, where each of the seven segments could be on normally, on with turbo, or on all the time. Once you figure a couple of segments out the rest should be simple.


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