hp28s a row doesn't work



#5

an entire row (from S to X and from STO to x) doesn't work anymore. I would like to have some suggestions about it and about how to open the calculator.

Thanks in advance

Fabio


#6

The problem is most likely one or more failed heat stake pins that hold the front and back case halves together, especially below the LCD. This causes a loss in contact between the keyboard connector and logic board.

It's not something that can be repaired... at least in a reliable or transparent way.

You can peel away the upper 28 logo label on the top half of the calculator and the lower keyboard surround label. Once they are off, you'll see a number of recessed plastic holes that are melted plastic pins that extend from the back half of the case into the front. Several will most likely fall out once the labels are off, those are what caused the problem, they shear off the back of the case. All the remaining heads will need to be drilled off for the case halves to separate.

Once done, there is no known good way to put Humpty Dumpty back together again...


#7

Thanks, Randy, for the interesting explanation. I have a 19B with a similar problem for the bottom row of keys (probably related to its having been mailed to me in an unpadded envelop!) By trial and error, I discovered that mine will work if I apply gentle (very gentle) pressure below the LCD. I need apply the pressure only once, each time I use the unit. How long this hocus-pocus will work remains to be seen.

Cheers, Tom

#8

thanks, randy, for your information. It's been useful not to solve the problem but to let me know what kind of problem it was...and much serious and hopeless! Indeed I find that if i press on the top of the display I can use all the keys of my old loved hp28s!


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