|Re: Fixing Classic LED segments?|
Message #5 Posted by Paul Brogger on 3 May 2007, 11:36 a.m.,
in response to message #4 by Dan W
As alluded to in one of my MoHPC "HP Memories" entries (#1), I used to give dramatic demonstrations of my HP-21's durability by tossing it to the floor. Eventually, the display started acting up.
As told in the article, I took the calculator apart, and removed the clear plastic lens strip from the display board by melting the heat stakes. Under a dissecting microscope (binocular, ~20 power or so?) I could see that the inertia of repeated impacts had collapsed some of the little jumper wires that connect the chip pads to the PCB traces. With a sharpened and de-burred plastic soda straw, I was able to pick up each of the collapsed wires and fix the display.
I imagine that, if there was any moisture in the display, your connecting wires (or chips?) might have gotten corroded over time in storage. I don't know how you would solder anything so tiny, but there may be a way. Take a close look at the chip/PCB connections and you may find your cause.
[Edited: Ooops! I assumed the 45 and 21 had similar displays. Sorry!]
Edited: 3 May 2007, 5:42 p.m.