Problem with my HP-41


I have a problem with my HP-41. I've removed the display to clean it. Now i only only see ramdom characters in display. I've check all contact in display using a digital multimeter and everything is ok.

If i check the batery i get 5.4V. I don't know where is the problem.



Hola, Luiz.

Check it the mainboard is perfectly aligned and in contact with the keyboard contacts. I had this problem many times, and in some of them I added two plastic washers between the case and the mainboard, fasten it a bit closer to the zebra connectors.

Did you disassembled the LCD assy? I mean, did you remove the "top" and "bottom" frames in order to clean polymer surfaces?

I have an HP15C that I removed the LCD frame and after reassembling the displays were fading and randomly ON and OFF. I disassembled it again, deeply cleaned the polymers and reassembled it again. It is working perfectly fine since then.

I read that the LCD assy is ESD sensitive and is easily dammaged if mishandled. Did you take ESD precautions?

Hope this helps.
Luiz C. Vieira - Brazil


Go down the line of connections with a probe and gently tug on each one. See if any pop loose from the LCD circuit board or possibly the keyboard. Also make VERY sure all solder flux has been removed. Clean the contacts and the back of the LCD with 91% isopropyl alchohol. Make sure none leaks onto the display window or you will be removing the LCD again to clean the white stains off.


The problem stay.

I've reasambled all circuits: unsolder and solder again the display, and main board. I've claned all contact.

I've changed four LR1 batterys.

I can see in screen something like this:
- -

just only a digit.

And the following labels: BAT USER GRAD SHIFT O

When i insert the battery pack, the HP41 goes on
If i press ON i can see in the screen: MEMORY sound a beep and return to initial state.
When i press R/S occurs the same, but not inmediately, first label GRAD goes to RAD and after one second i can see the MEMORY message and ear the beep.

There is not response to others keys.



The problem is not allways the same. If i remove memory modules and i connect the battery i can see label USER and i i press key 1 or 2 i can seen in the display these digits, but i can press keys very strong.

I think maybe a problem with contact between main board and keyboard.

Do you know how can i solve this problem?




can you tell us what sort of connector you have between them both? I know three different zebra connectors used to do so, ant the best one is the most difficult to deal with: the one with very thiny golden-plated cooper trails.

Best regards.

Luiz C. Vieira - Brazil

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