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HP Forum Archive 14

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How to open up an HP-28C
Message #1 Posted by John Nelson on 22 June 2004, 5:45 p.m.

Anyone know how to open up a 28C? I am having problems when I turn mine on, it goes off or flickers. I find that if I squeeze the top portion a bit (front to back) it fixes things, so I'm thinking something must be loose inside.

I would think you would need to take the four rubber pads off the back and then there might be screws or something.

Also, is there something I can use to replace the rubber pads? I hate to take them off, but this is driving me buggy.

Thanks!

      
Re: How to open up an HP-28C
Message #2 Posted by Randy on 22 June 2004, 7:24 p.m.,
in response to message #1 by John Nelson

Peeling the feet will reveal nothing.

Repeat of a previous post (with modifications):

Open it you can, repair is very questionable.

Opening a 28 is for all practical purposes, a non-reversible procedure. Kinda like a calculator post mortem. Reminds me of the Monty Python skit where John Cleese says "I can't take him, he's not dead yet." But he will be. It's time to bury your 28C.

If you want to have a look-see and assuming you are working on the right side:

Peel off the 28C label at the top of the unit and then peel off the label surrounding the keyboard. Most likely, several small plastic rivet heads will fall out. Those broken rivets are your only problem. The ones that don't fall out, drill out by hand by rotating an appropriately sized twist drill until the head of the plastic stake releases. Once they've all been removed, the case halves will separate.

There is no good way other than gluing to reassemble. Some have mentioned small screws or bolts to hold the halves together.

Good luck.

The most common problem I've encountered is a loss of a row or column on the keyboard. It is caused by internal case part failures, you'll see the cause should you open yours. The plastic pins that hold the front and back case halves together break off and allow the case to separate, breaking the connection between the keyboard and logic board. If you press down along the raised bottom edge of the case, below the LCD, you can usually get the unit going again but it's only temporary.


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