Lower Post Repair part - glueless

Piece to repair HP41c full nut series lower screw posts

Lower Post repair

Material needed:

• Lower post repair piece
• drill bit - small
• Long lower post screws

Let's assume that both posts are broken or cracked. The effect of this cracking is that the screws do not do their job. Usually, using longer screws may help, but this typically is short lived since the cracks will continue downwards. Once the pressure between both halves is softened, the calculator doesn't work anymore. The solution is to repair the broken posts.

Old methods to repair broken post is to glue them (but this doesn't hold together too long) and to tie them down with very small gauge copper cable, applying pressure so that it holds together. This may solve some cases, but not when the screw path has been destroyed - maybe due to strong tightening of the screws.

Other repair methods have been proposed, including drilling down the screw and placing in its place a cylinder with screw path, glued in place. We tried this method but there was a problem: the torque used to screw resulted in cracked glue and the cylinder separating from the substrate - every time.

Our method was devised with three goals in mind:

1. Try to avoid the torque from the screw deforming the part
2. Try to ensure that the front part of the calculator is pulled up when screwing the back side on.
3. Try to be compatible with all known zebra connectors - including our own.

The piece that we have designed requires drilling the old posts to 4mm below the circuit level. The design on the piece is such that the grip of the lowe part of the post is expanded when a long screw is introducing, fixing the part inside without the need of glue.

Remove with a X-acto knife the rivet head between the 1 and 2 keys so that the part remains flat on the keyboard. Place the part in the holes. It may require some pressure to do so.

Place the zebra connector on top of it. Place the circuit on top of the set, and then any spacers if needed. Then assemble the calculator, screwing the long screws with sufficient down pressure to make sure the part is secured and not taken out when arriving to the end. Then test the calculator