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Broken HP 28S battery cover repaired with brass sheet
02-12-2016, 11:59 PM
Post: #1
Broken HP 28S battery cover repaired with brass sheet
The battery door of an HP 28S is kind of fragile, but parts of the case are also prone to crack away. That has been discussed elsewhere on the forums, along with some fixes. Common ones involve tape or just a rubber band around the case to hold the door in place and an unusual fix was shown with a steel strap that extended from edge to edge.

I have a 28S with the tiny corners of the door broken away and a portion of the case meant to guide and hold the door also cracked off (but not lost).
[Image: Close-up%20of%20HP%2028S%20broken%20batt...0guide.JPG]

Gluing the piece of the case with cyanoacrylate was not strong enough to hold against the spring pressure, so in addition to the glue, I drilled a tiny hole and inserted a brass pin through it and into the case.

The drill is a size 76 (~.52 mm diameter) and I used a hard, tapered brass pin of the type sold for clock repairs. It only needed a very short length of the pin, so I clipped it off near the surface and pressed it into place.

To take the place of the battery door, I cut out a piece of brass sheet (0.8 mm thick) using a jeweler's saw and filed it to fit then bent it over.

The brass is rigid and a sufficiently snug fit that it holds in place all by itself. Because the brass is conductive, it serves both as battery contact and cover.
[Image: Close-up%20view%20of%20brass%20battery%2...%2028S.JPG]


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02-13-2016, 07:55 AM
Post: #2
RE: Broken HP 28S battery cover repaired with brass sheet
Another Clamshell saved. Nice work!
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02-19-2016, 08:14 PM
Post: #3
RE: Broken HP 28S battery cover repaired with brass sheet
Has anyone tried to replace the metal springs instead? It seems that the ones used are just too strong and end up putting too much pressure onto the place where the cover connects with the case. I don't have my HP28S in front of me, so perhaps this idea may simply be impractical.

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