41CX with bad row of keys....



#9

Frustrated. I just can't get a fully working 41CX anywhere. I continue to purchase "fully working" units, only to discover they are completely dead, or in this case, has a dead row of keys (the trig row).

Do you think a dead row is a loose interconnect problem? I hate opening these up, because it seems like they never go back together tight again. The seller might take it back, but unfortunately it came with a printer, working card reader, and other goodies and I'd kind of like to keep those.


#10

Yes it could be a connection problem between the keyboard PCB and the CPU PCB in fact since you lost an entire row that would be my first suspect. This could be a problem with a cracked or broken post, if you put the calculator on a table top and press down firmly on the sides next to X and 3 does it help? If you have a damaged post you may even see the top half move slightly when you press down on it.


#11

I've come up with a very reliable solution to the cracked post problem. Replace them with a standoff.

I first tried a 4-40 standoff. The typical OD(.187) fits nicely into the hole vacated by the post, but the 4-40 screw is too big. The heads of most screws require you to modify the back case. I am going to try a 2-56 standoff next. It has a .156 OD, but I should be able to use a standard screw and not mess with the case.

#12

No, pressing down doesn't help any. Everything feels very solid.


#13

Most of the strange behavior I have encountered can be blamed on this contact. I'm not saying yours is to blame, but all takes is one of the gold contacts shown in the picture to loose contact for this to occur.

#14

Halfnut or Fullnut model? Big difference internally.


#15

I should have specified in the original post. This is a fullnut model.


#16

The logical problem would be a loss of connection between the keyboard and logic board for that keyboard column/row. Corrosion/loss of connection/etc. Disassemble and have a look, the only way to know for sure.


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