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HP41C Display Problem
05-18-2020, 11:18 AM
Post: #1
HP41C Display Problem
I'm having this problem with the display of my 41C. It was working perfectly, it gets very little use and then one day I turn it on and...

[Image: 49908081473_b4cb027dc5_b.jpg]

I've put new rechargeable batteries in it: no joy. As you can see, the contacts are as clean as anything... Is there anything I could try?

[Image: 49908092708_7f9abfa652_b.jpg]

TIA,

Tim
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05-18-2020, 08:37 PM
Post: #2
RE: HP41C Display Problem
The LCD is soldered onto the keyboard PCB so it's not a bad contact there. However, the CPU board (yours is a fullnut) is maintained in contact by pressure exerted by screws that screw into posts that are part of the front.

These posts are notoriously fragile in 40-year-old calculators and my bet would be on the posts in your 41C having broken over time.

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05-18-2020, 10:05 PM
Post: #3
RE: HP41C Display Problem
Repair a broken post only with solvent based plastic model cement, the stuff is like water, not thick at all. Do not repair with cyanoacrylates (super glue), that will not work.

A good reference: https://www.hpmuseum.org/cgi-sys/cgiwrap...ead=197569
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05-19-2020, 01:56 AM
Post: #4
RE: HP41C Display Problem
Try squeezing the top and bottom case of the calculator together. If it solves the display issue, broken posts are probably the cause.
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05-19-2020, 10:12 AM (This post was last modified: 05-20-2020 09:42 AM by Ignatz.)
Post: #5
RE: HP41C Display Problem
Thanks, all... squeezing was my first go-to... no joy, there, I'm afraid... Like I said, The calculator has simply sat on my desk since I've had it: the problem appeared one morning at switch-on. I'll try opening it to have a look.

I forgot to mention that it showed exactly this problem when I first received it, but I think that was due to its having been sat outside in my delivery space in freezing temperatures. As it warmed up, the LCDs came back to life... any chance the two things are connected?

TIA,

Tim
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05-19-2020, 10:14 PM
Post: #6
RE: HP41C Display Problem
I don't know about the 41C LCD in particular, but LCDs in general can be very temperature sensitive, and even damaged by slightly too-high temps.

Also, you may be experienced at 41 repair, but note I've seen people say that the best way to get broken posts is to open one up.

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