HP-11C problem

[Rogier]

Hi, my first post. Unfortunately it's problem. The lower right hand corner of my HP-11C display seems to be 'sagging'. Anyone know this problem? Can the display come loose altogether? Can this damage the calculator? Any way to solve it without taking the calculator apart?

Hope you can help me.

[damaltor]

I suggest unscrewing the four screws under the rubber pads, carefully removing the back plate (watch out, there are two tiny, but soft springs which are easy to keep if you open it carefully) and look at it from the back side. also, if you want to, you could add a photo to your description, maybe someone has already seen something similar.

[Rogier]

Thanks! Here's a photo.

[Zaphod]

You will have to remove the back cover , remove the four feet carefully (as you will be reusing), four screws underneath

But then you face the same problem as someone in another thread today , you will need to remove plastic melt stakes (but leave enough post so you can remelt) so you can remove the PCB and gain access to the display.
I’m guessing it uses a self adhesive pad around the display and the front frame , but you’ll soon know how to sort it out once you get that PCB out.

Take a look at this for disassembly techniques : https://m.youtube.com/watch?v=qERwsdjoX7c

I wouldn’t attempt it unless you feel confident as you can quickly mess up those posts so you will never get a strong fixing via the post-repair post melting technique.

[Rogier]

Doesn't sound appealing. Any idea what may happen if the other corners start to let loose too? Will that impai calculator function? So far it is working fine.

[Zaphod]

(04-25-2018 08:21 PM)Rogier Wrote:  Doesn't sound appealing. Any idea what may happen if the other corners start to let loose too? Will that impai calculator function? So far it is working fine.

What I might suggest is remove feet and screws and see if there is space to push some packing material in between PCB and LCD back ?.......

If it comes loose all round it’ll let in (more) debris and will be supported only by it’s solder connections

What I don’t understand is from the pictures shown here: http://www.decodesystems.com/hp11c-apart.html

The LCD rests on the PCB , so for the display to sag means the PCB is also sagging ..... which could mean some of the melted post tops (shown in video and photos above) have come adrift ....

Never had one to bits to the extent of removing the PCB so I can’t really offer any more help

Do the keys near the sagging end of the display still have the same ‘feel’ ? Or do the feel a bit soft ?

What’s even more confusing is that latest link shows the PCB mounted in the rear casing , not in the front like the YouTube video.

I’d get those feet off and screws out and take a look inside, what have you got to lose to see if the PCB is held in the rear or the front casing.

[Rogier]

I'll look into it. The keys feel fine. All of em. From what I see of HP-11c interiors this shouldn't happen. At least not without the entire keyboard "going down".

[Rogier]

I looked carefully at the pictures on http://www.decodesystems.com/hp11c-apart.html. Particulary this picture:
    That shows the display encased in some sort of metal frame that rests on the PCB with something like 8 metal supports.

From this picture and what I see on my calculater I deduce that:
- The PCB is intact (all keys are working fine),
- The metal frame that holds the display appears to be in place too. It would take major damage to 3 or more feet or a break in the PCB to get that to move
- So I think that my display is sagging inside the frame
- That frame looks like something you shouldn't mess with
- Opening the calculator would mean messing with the heat-stakes and I don't know if I will get them back again (although maybe I won't have to: I read earlier models don't have them, and my 11C has a serial nr starting with 2219A, so maybe it's an early model).

I decided not to open my calculator, since its working fine and I expect I won't find anything I can fix. Instead I put the vacuum-cleaner set to maximum suction over the display, and that partially corrected the problem. Now its hands off the display and hope for the best.

Thanks for your tips. If I ever open the calculator I'll post my findings.

[damaltor]

I guess i would not go further, too. As long as it works i would live with the sagging display.