HP-41 in the dark

Yes, I have the same problem as you. When you feel the urge to program your precious Hewlett Packard HP-41 calculator in the middle of the night, you would have to turn on some light source. A lamp would wake up your wife or the kid that decided to occupy half of your bed. You need a small light source.

And when you are out with your telescope inventing new ways to justify the use of your 30 year old calculator, you need some light source that doesn’t kill your night vision.

A while back I made a plug-in module for my HP-41CX that had a LED attached to two wires coming out from the module. As I didn’t know which of the internal module pins to solder the wires to, I ended up with a Porta-Lite module where the LED would always be on regardless if the calculator was turned on or not.

Yesterday I decided to open up the module and do it right this time.

Yes, it’s a simple hack. And for those hardware gurus over at the HP Forum, this would seem pretty trivial. But for me, a predominant software guy, it’s a small hill. A small hack, but a useful one.

Ok, “pics or it didn’t happen” – so here they are:

5 thoughts on “HP-41 in the dark

  1. Don’t you have a volt meter that would give you the polarity of the output? 😀

    1. I do – but the first time I thought I had it right, I didn’t.. superglued the module and got one that continually would drain the batteries… 😦

  2. What a flashback. Tom Hooper made and sold the Port Lite (or was it the Port-X-Lite?) back in the early 80s for the 41. It had a switch on the exposed side of the module. Mine is buried away in a box somewhere.

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