PC-100 US Version

[Maximilian Hohmann]

Hello!

Sorry for the off topic, but people who repair calculators seem to like repairing other stuff too :-)

(03-14-2022 04:53 PM)rprosperi Wrote:  Indeed, I have a D-cell Maglite that needs the same work. What clue(s) can you summarize to tackle this, Max? I was going to start with letting the swelled end soak in some vinegar to loosen it, then switch to a flat-blade screwdriver and light hammer...

I guess I should have taken some pictures...

Pouring some vinegar in will certainly make things easier because it dissolves the electrolyte which may have accumulated between the batteries and the housing. But my batteries had swelled considerably so that alone was not enough.

To remove the upper two batteries I basically used the method shown in this video: https://www.youtube.com/watch?v=3aZCns5yaLU
Drill a hole (8mm approx.) into them, drive a thick wood screw with hexagonal head into them and either pull or hammer them out.

But the third and fourth batteries are too deep inside for that method to work, unless you can get hold of a very long drill and screw. So the flashlight needs to be opened from the top as well. Remove the rubber guard over the switch (it can be popped out with the tip of a screwdriver) and loosen the screw that fixes the switch/lamp holder unit in place. You will need an allen key for that, I guess it is an american size but one of my metric keys worked also, there is no big torque that needs to be applied.

Without the batteries in place this unit would normally now just fall out the back end of the flashlight, but here of course the stuck batteries are in the way. To get it out the front side, a securing circular spring has to be pryed out of it's groove. This is the difficult part because the spring needs to be moved out of the groove and pulled upwards at the same time with considerable force. And the operation is performed mainly by feel because it is all very tight and difficult to see - a bit similar to lockpicking.
The only way I could get the spring out was to drill a shallow hole (using a 5mm drill, a smaller one would have been sufficient but was not long enough to reach all the way down) next to one end of the sping (see the photo below).
Now I filed a little nick into the side of a screwdriver close to the tip. And using this "special tool" and the extra room provided by the drill hole I could apply enough leverage to get the end of the spring out of it's groove. With luck it gets caught in the indentation made into the screwdriver and can be pulled out. I still took quite a few attempts...

Now the other two batteries are accessible just like the first two. After that I used plenty of vinegar to remove the remainig electrolyte, applied a thin coat of silicon oil and put everything together again. It looks like new and if no more batteries leak inside may last another 20 years!

Regards
Max

It looks as if the spring is y-shaped but that's only the reflection!