The Museum of HP Calculators

HP Forum Archive 10

[ Return to Index | Top of Index ]

dismantle 48 series
Message #1 Posted by Mike on 17 Jan 2003, 2:16 a.m.

I have a 48 series calculator that is on the blink, sometimes it works then it sort of resets itself or turns its self off. I have 2 questions, 1) has anyone had this happen to them before? and 2) how do you dismantle one without damaging the case??

Thanks Mike

      
Re: dismantle 48 series
Message #2 Posted by Randy Sloyer on 17 Jan 2003, 9:20 a.m.,
in response to message #1 by Mike

Does it come back to life with a "Try to Recover Memory" message? Or does it retain memory and display the stack as it was before dying?

Anything been spilled into the keyboard? Most probable cause of what you describe.

Opening a 48 is best done by prying open at the appropriate locations. There are 10 heat stake posts that can be "popped" and 6 side catches that must be defeated. Pops open in few minutes and they snap back together like a Lego set. Don't try to peel the bezel off - it's a disaster and the "cutting method" is a total hack job.

            
Re: dismantle 48 series
Message #3 Posted by Paul Brogger on 17 Jan 2003, 7:05 p.m.,
in response to message #2 by Randy Sloyer

I've found the "cutting method" to work fine -- I've opened a few that way.

Instructions for the "cutting method" may be found here.

Regarding the other method described, I wonder how one gets enough grip on the front & back to pop the heat stakes.

Can anyone point us to instructions for the other method?

Thanks, (and good luck!)

Paul B.

            
Re: dismantle 48 series
Message #4 Posted by Mike on 17 Jan 2003, 10:26 p.m.,
in response to message #2 by Randy Sloyer

It comes back to life and displays the stack as it was before dying. As far as has anything been spilled on it I don't know, I bought it second hand so it may have. I will look over which way may be the easiest way to open it.

Thank you to Randy and Paul.

      
How I open a 48
Message #5 Posted by Randy Sloyer on 17 Jan 2003, 9:06 p.m.,
in response to message #1 by Mike

Having tried both cutting the stakes from inside the calculator and peeling the bezel off a dead 48G with a heat gun, I was less than satisfied with either method. I was ruminating on this weeks later, thinking the 48 was just a big pioneer with more heat stakes when I found this article: http://www.hpcalc.org/details.php?id=4701 I stumbled a bit with the language, but the concept was clear. They can indeed be popped open. I tried the method and it was deceptively simple, it became a matter of finding a tool to do the job without marring the calculator.

I found that tool in the form of a wooden craft stick. I use the ones that are approximately 1" wide, 6" long. The wood is typically (and should be) softer than the plastic, so it does not leave marks like metal tool suggested in the article.

Using the craft stick, I cut one end off straight and shaved one side to form a chisel. It slides right under the top lip of the case. The long stick is a great lever to pop the heat stake mushrooms out. The top four stakes are easy. Just slide the stick in and lift up. The two stakes on each side pop right open. I then take another craft stick that has been cut on a 45 angle and shaved again to be an angle chisel. This can then be slid down the side of the case to release the three catches on each side. Back to the straight chisel and slide it in and pop the six bottom heat stakes and it's open. Do the bottom six in a set of two topmost then the remaining four. Once the outer bottom left and right are free, the center two can be popped like pulling the back off a pioneer machine.

You may bend the keyboard plate a bit at the end on the last two stakes, but it is easily straightened. I have found the G and G+ easier than the GX due to the expansion connector limiting access to the bottom six stakes.

When reassembling, straighten the top plate, especially at the top corners as these are usually bent upward. I then use a pair of flat jawed "duck bill" pliers to bend the seven locking tabs of the keyboard plate into the proper position so they relock into the case bottom. Prepare the stakes, using the same pliers, grab the top of a stake and twist 360 repeatedly, using a light pressure to compress the mushroomed end of the heat stake into a cylinder about the same size as the hole into which it is being inserted. Repeat for all ten stakes. I trim a small amount of the flash from the top of the stake so it does not extend too far and deform the keyboard bezel. I do not shave down the sides of the heat stake as you want the mushroom at the top of the stake to lock back into the keyboard plate.

Place the two halves together, start at the top and squeeze each stake area with just finger pressure. The whole thing snaps back together with a satisfying click. A drop or two of plastic welding solvent cement on each stake can be used if you want a really tight case. If you chose to do this, tightly tape the whole thing together and leave overnight to allow the solvent cement to do its thing and really lock the two halves together.

You can still disassemble in the same manner after gluing. I had one unit I must have popped open three or four times until I found the bottom tab of the positive battery clip was shorting out on the keyboard plate once the batteries where installed. That one is still tighter than many cases I see on new units. It's the same G+ that I installed a black on gray screen in from a dead 49 :-)


[ Return to Index | Top of Index ]

Go back to the main exhibit hall