41c repair



#14

I've got a 41C (2051 serial) which doesn't operate if the battery pack is fully inserted but seems to work fine if it is only half inserted. Does anyone here have any idea what the cause of this will likely be? I'm guessing the battery contact/port block isn't making good contact with the board below and the added pressure of full insertion is causing problems but I'd prefer to confirm before I open it up.

- Pauli


#15

Is there a piece of corrosion right on the forward, leading edge?

Your analysis seems plausible to me.

#16

you might be able to confirm this by placing the calculator on a table and gently pressing the front face (on the top left- and right corners) while trying to turn on the calculator. It sounds like it may be a broken post to me, though.

#17

My guess would be that the front pair of the four port block locating pins are sheared off along with damage to the bosses for the long case screws.


Edited: 27 Feb 2011, 2:33 p.m.

#18

Hi Pauli, if you need help with it, remember I'm just 80 klms south of you.

Cheers,
John


#19

John,

Thanks for the offer. Will see how I get along.


- Pauli

#20

Thanks for the idea. I feared a broken post, I'll know for sure when I disassemble. Sad really, the calculator is in great cosmetic condition.

- Pauli


#21

No split or broken posts!

The two posts holding the CPU board in place have nuts on them to hold the PCB onto the connector.


- Pauli

#22

I think I've figured this out. The battery / module connector had slightly flattened foam/felt which is stopping the electrical connection.

I took the connector out and put it into my 41cv and the problem appeared on that calculator. Swap back its original connector and it comes good. At this stage I've not tried swapping the cv's connector into the 41c.

My question now is what is the best way to fix this?
The padding is only very slightly squashed.


- Pauli


#23

Hello Pauli,
You can add a strip of similar material to recover what is missing.

Ignazio

#24

This worked for me many years ago, but is up to you to see if it fits your case: Take a piece of thin two-conductor cable (the kind used for small headphones, or two lines of flat ribbon cable), and slip it from one side of the connecting block, setting it between the foam and the flexible circuit film. When in place, looking from a side, you would find (bottom to top): the main circuit board, the flex circuit film, the cable, the foam and the plastic block. The extra thickness will ensure good contact between the main circuit and the flex circuit. Of course, the cable serves no electrical function, and care should be taken to avoid any conductive thread protruding at the ends.

#25

Hi Pauli,

Good find. Unfortunately it's virtually impossible to replace the foam piece without wrecking the flex circuit. Newer 41 calcs had that packing made of silicon type rubber instead of foam. I'd try something along the lines of the others are suggesting and slip something non-conductive between the foam and the flex PCB.

Good luck
John


#26

I slipped a toothpick in it. :)


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