Set of zebra + lower post repair piece

Assembled Battery-back port module repair kit for the often damaged flexible PCB in the battery bay (and I/O ports) of the HP-41c range of calculators.

It is made of a flexible circuit, already collated to an 3D-printed battery-expansion ports module, ready for assembly within your HP41c. Standard colour of the base is black, but it can also be ordered in white (like the pictures)

Instructions for battery and ports module

Open the calculator

First remove the rubber feet. To do so, use a small, flat screwdriver and introduce it beneath the rubber, taking care of pulling also the adhesive sheet that glues the rubber to the calculator. Try to make here a good job because usually you will have to reuse the rubber feet when you're done. Put the rubber feet aside so that they don't hinder the work (they have an uncanny ability to adhere to shirts, tools, calculators and eventually get lost.

Unscrew carefully and slowly the four screws beneath the rubber feet. Turn gently the screws: they operate on plastic that, after 30 years, is very brittle and fragile. It is very easy to break a screw post or "overdo" the thread.

Remove the back side of the calculator and put it aside. For comfort, remove also the intermediate piece between backside and main body. Later we will take care of putting it the right way, since it has two ways.

Remove the old piece

Now it is the time to remove the damaged battery-ports module. To do that, first remove all 4 module covers or modules; then pull the module vertically and carefully, since there are four plastic tabs in the calculator used to secure it, and it you do horizontal movements you can bend or break them. Yes, they have also became brittle!

Sometimes grit and grease have "glued" the old piece to the backside. It will be very difficult to remove it. Be aware that it is NOT glued by design - this is an unwanted effect of grease, grit and time. To remove the piece in this case, try pushing up with a screwdriver on the back module connectors. Increase upward force until eventually it separates from the body. Clean the backside plastic with water and soap or a lenses cleaner. It may happen that one or both of the screw supports are broken. You will have to repair it beforehand with the broken back repair piece.

Once the backside is clean and free from the old battery module, insert the new one carefully, making sure that the 4 vertical tabs are not bent. This is done without the module covers in. Be sure that it goes down to the calculator body. 

After it has been installed, put the module covers or modules so that they push the piece in place.

Reassembling

You can now reassemble the calculator. Put the keyboard face down on the table. Then, put the intermediate piece with the open side upwards, taking care that the wider part is up, like "opening up"  (this piece has a slight angle when looked from the front of the open side). This is important for the calculator to close properly. See picture.

Then put the back side on top. You can start by any screw - I usually start by the upper ones. If everything is ok, you will be able to screw through the piece and into the calculator. Screw carefully not to break the threads. If that happens, repair will be substantially more complex and will need the upper post repair piece and some drilling.

And that's it!!

Please be sure to eliminate rusting from the main board with Caig DeOxit (best), WD-40 (not as good) or other suitable cleaner, applied with cotton buds.

Save your HP41c !!

Assembled Battery-back port module repair kit for the often damaged flexible PCB in the battery bay (and I/O ports) of the HP-41c range of calculators.

This is the FLAT version, when the screw head domes are broken and grinded down - see pictures.

It is made of a flexible circuit, already collated to an 3D-printed battery-expansion ports module, ready for assembly within your HP41c. Standard colour of the base is black, but it can also be ordered in white (like the pictures)

Instructions for battery and ports module

Open the calculator

First remove the rubber feet. To do so, use a small, flat screwdriver and introduce it beneath the rubber, taking care of pulling also the adhesive sheet that glues the rubber to the calculator. Try to make here a good job because usually you will have to reuse the rubber feet when you're done. Put the rubber feet aside so that they don't hinder the work (they have an uncanny ability to adhere to shirts, tools, calculators and eventually get lost.

Unscrew carefully and slowly the four screws beneath the rubber feet. Turn gently the screws: they operate on plastic that, after 30 years, is very brittle and fragile. It is very easy to break a screw post or "overdo" the thread.

Remove the back side of the calculator and put it aside. For comfort, remove also the intermediate piece between backside and main body. Later we will take care of putting it the right way, since it has two ways.

Remove the old piece

Now it is the time to remove the damaged battery-ports module. To do that, first remove all 4 module covers or modules; then pull the module vertically and carefully, since there are four plastic tabs in the calculator used to secure it, and it you do horizontal movements you can bend or break them. Yes, they have also became brittle!

Sometimes grit and grease have "glued" the old piece to the backside. It will be very difficult to remove it. Be aware that it is NOT glued by design - this is an unwanted effect of grease, grit and time. To remove the piece in this case, try pushing up with a screwdriver on the back module connectors. Increase upward force until eventually it separates from the body. Clean the backside plastic with water and soap or a lenses cleaner. It may happen that one or both of the screw supports are broken. You will have to repair it beforehand with the broken back repair piece.

We assume that the screw supports are broken. Grind down to flat the screw supports with a dremel-like machine with some grinder head.

Once the backside is clean and free, glue the lower side of tthe module with E6000 glue, including putting some in the holes where the tabs are going to be. Then insert the module carefully, making sure that the 4 vertical tabs are not bent. This is done without the module covers in. Be sure that it goes down to the calculator body, and put pressure on the sides with cloth pegs to ensure good contact. Put also the module in to ensure good vertical position. Leave it overnight.

Reassembling

You can now reassemble the calculator. Put the keyboard face down on the table. Then, put the intermediate piece with the open side upwards, taking care that the wider part is up, like "opening up"  (this piece has a slight angle when looked from the front of the open side). This is important for the calculator to close properly. See picture.

Then put the back side on top. You can start by any screw - I usually start by the upper ones. If everything is ok, you will be able to screw through the piece and into the calculator. Screw carefully not to break the threads. If that happens, repair will be substantially more complex and will need the upper post repair piece and some drilling.

And that's it!!

Please be sure to eliminate rusting from the main board with Caig DeOxit (best), WD-40 (not as good) or other suitable cleaner, applied with cotton buds.

Save your HP41c !!

This piece is for repair of HP41c full nut calculator, substituting the damaged or corroded zebra connector that links the main board with the processor circuit. New design in a single piece, with 50 times more conductivity than elastomeric contacts.

Installation instructions

Open the calculator

First remove the rubber feet. To do so, use a small, flat screwdriver and introduce it beneath the rubber, taking care of pulling also the adhesive sheet that glues the rubber to the calculator. Try to make here a good job because usually you will have to reuse the rubber feet when you're done. Put the rubber feet aside so that they don't hinder the work (they have an uncanny ability to adhere to shirts, tools, calculators and eventually get lost.

Unscrew carefully and slowly the four screws beneath the rubber feet. Turn gently the screws: they operate on plastic that, after 30 years, is very brittle and fragile. It is very easy to break a screw post or "overdo" the thread.

Remove the back side of the calculator and put it aside. For comfort, remove also the intermediate piece between backside and main body. Later we will take care of putting it the right way, since it has two ways.

Remove the processor.

There are two possible cases:

• In the old calculators the processor circuit is pressed down to the main circuit by a couple of nuts screwed on the plastic posts. The post do not have any thread themselves - the thread is carved by the nut itself. These have to be removed with care because you risk to break the post, by unscrewing counterclockwise. More than a couple of in and outs and the post will break for sure. Once done, lif the circuit. 
• In the newer ones, this pressure is exerted by two cylinders around the screw holes in the back side of the case. These are not present in the old models. You just need to lift the circuit.

Once the circuit is lifted, you will see the zebra connectors. These may be of three different types (thanks to monte Dalrymple for the image)

• The left one can be reused if treated with care and not corroded - clean it with paper embedded in Caig Deoxit. However, it doesn't work in some circumstances and there is no clear reason why.
• The second is completely useless and will need to be replaced. Every time.
• The thirs type is the best of the lot and can be reused with care if not corroded. It is also sensitive to friction and can be easily damaged. Discard if corroded.

Reassembling - closing the calculator

You can now reassemble the calculator. Put the keyboard face down on the table. Then, put the intermediate piece with the open side upwards, taking care that the wider part is up, like "opening up"  (this piece has a slight angle when looked from the front of the open side). This is important for the calculator to close properly. See picture.

Then put the back side on top. You can start by any screw - I usually start by the upper ones. If everything is ok, you will be able to screw through the piece and into the calculator. Screw carefully not to break the threads. If that happens, repair will be substantially more complex and will need the upper post repair piece and some drilling.

And that's it!!

Adhesive circuit for the often damaged flexible PCB in the battery bay (and I/O ports) of the HP-41c range of calculators. Shipping included in price.

Designed to be folded in shape, it has an adhesive back with a 3M Very High Bond surface.

Please looked to the attached manual.

Shipping included in price.

Set of 8 pairs of spacers for nut-screwed full-nut HP41c calculators. Substitutes the nuts that are screwed on the lower posts to secure the circuit. These nuts can only be used a couple of times before the posts are destroyed. The diameter is just right for the original posts, and the height can be chosen to adjust perfectly so that the case can be closed completely and the pressure to the zebras is transmitted efficiently.

The heights provided are: 1,2mm, 1,4mm, 1,6mm, 1,8mm, 2,0mm, 2,2mm, 2,4mm and 2,6mm

Two long screw for the lower screw posts of HP41c calculators. As they are slightly longer, they can still hold when the original screws have destroyed the thread.

The screws are too "self-threading". Made in 304 inox steel.

Two long screw for the lower screw posts of HP41c calculators. As they are slightly longer, they can still hold when the original screws have destroyed the thread.

The screws are too "self-threading". Black 314 Stainless steel (A4)

Two long screw for the lower screw posts of HP41c calculators. As they are slightly longer, they can still hold when the original screws have destroyed the thread.

+ two screws for the upper posts - standard size

The screws are too "self-threading". Made in 304 inox steel.

4 pieces for repairing HP41c back cases.

As many units suffer from broken upper screw supports on the back side of the calculator, we have created pieces for the repair of the back side of the HP41C - which offer bigger surface for adherence and also serve to hold the battery assembly in case the little wings in the back side are broken.

Includes shipment within Europe

Instructions for use of back side repair piece.

1. Be aware, before everything else, that the piece has a right side and a left side. This is due to the space for the tabs in the calculator that keep the battery-port assembly in place. You need to be aware of this at all times - more so if you want to cut it as explained below.

2. Decide whether you will replace both sides or just one. The decision is easy when both are broken, but if one is not, you'll have to check whether the old standing support will withstand the pressure for long. Our recommendation is to replace both sides. If later one of the sides breaks down, the repair will be much more difficult and probably less solid. And you have already paid for both sides!!

3. If you are going to replace just one side, cut with a hobbyist scissors just the side you don't need, according to picture enclosed, again, be careful of cutting the side you dont need, since the piece has a single correct orientation!. The rest of the piece will serve to increment the glued area, better align the piece in place and also to better support the battery-port assembly.

2. With a Dremel machine, file and level the area that had the support. You don't need to remove the tabs in between the two screw post, but you need to remove them if they are twisted or half-broken.

5. Put the piece in place. There is only one "right" way. The cross part is tight because it is needed to properly locate both holes at the extremes. Do not force it. Please make sure it is not bent downwards. Make sure it makes good contact. Remove the piece.

6. Put some glue in the bottom of the piece. Do not put too much or it will go out when pressed. We have used E6000 black glue with good results. Do not use cyanoacrylate glues. Put the piece back in place. Press and remove with a stick or a blade the excess glue, if any. If the screw holes are partially obstructed by glue, pass a screw in the opposite direction (to avoid separating the piece from the back side).

7. Secure the piece in place with a pair of clamps - lighter pressure like clothes' pegs will not be enough. Be careful that there is no excess glue from the other side of the case and the clamps are adhered to the piece! Leave for 24h for the glue to cure. And you're done! You have a repaired back that will withstand a lot of abuse again.

8. The piece is designed to accept both the original and the new battery-ports assembly - so you need to press it down to have it in place. The screw holes should fit a little bit tighter than in the original calculator, but should be perfectly aligned with the assemblies and the screw posts below.

Also, if you're buying from the US, it is maybe better to buy it directly from Shapeways there (just click on the link)