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calcupen?

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767Geoff

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calcupen?

Post12 Jan 2008, 06:02

Just picked up a calcupen. What type of batteries and does anyone know how to open one up if required.

At the present time the middle horizontal segment for all eight Led's does not light up. Hoping that it is a cold solder joint or something as easy to repair (?).

The functions all work correctly except for the display.

Any ideas would be appreciated.

Cheers, and Happy New year all!!!!!!!!!
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retroleds

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: calcupen?

Post12 Jan 2008, 17:45

Type "N" battery....looks like a AAA, but only about 2/3 as tall. Shame about the display...take some pictures and give us some details for posterity, please. A new ink nib can be made from a "Cross" or some other brands refill - throw in the freezer, pull out and quickly cut(small tubing cutter that uses a sharp wheel is perfect) and place a dab of slow cure epoxy over the cut end....it will be drawn in maybe .5mm in as the ink thaws and shrinks. It works!
http://www.retroleds.com - Sales of vintage LED, LCD, analog watches, parts and gadgets - repair tutorials & tips
Nov. 2022 - back in business!! BItter divorce is in home stretch, come grabs some great deals, I had to open the safe . . . damn attorneys. piss.
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: calcupen?

Post29 Jan 2008, 23:55

Just found this site and this post.

I thought I would add, I have one of these calcu-pens in it's presentation case. The calculator still works as well as it did when new. The buttons are too fiddley to be practical. the size "N" battery is also known as an MN9100. The four unused pen tips I have have long since dried up though.
I thought I would post some photos when I had time to take them but then I found the link below which also includes scans of the operating leaflet.

http://www.vintagecalculators.com/html/ ... cupen.html

Roy
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767Geoff

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SUCCESS

Post11 Feb 2008, 21:26

I will be taking photos of the dis-assembled calcupen including some hints. I am in the process of cleaning the contact cement off the top shell and the pen, smoothing out wrinkles in the top cover, cleaning contacts and allowing the electronics to dry.

It was a cold solder joint causing the display to drop an element all the way across. Soldering all the LED joints has solved this. More to follow with pics on dis-assembly as it is certainly not apparent how to do this.

Cheers, Geoff

PS: Roy thanks for the url and the info..
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: calcupen?

Post11 Feb 2008, 22:32

Geoff: It should/would have only required one solder joint(albiet the correct one) to be repaired if the same segment was out on all digits - the bond between the decoder and the particular trace that feeds the particular segment in all digits. I'll quote a small section from Louis Zanoni's book, since it is explained quite succintly - straight from "the man". The blue text is my inserts, for clarity.

" Note that all "a" [we will designate the failed segment as "a"] segments are connected together by one conducting line on the substrate. The same is true of all other segments of the display. You must be wondering by now why all the digit's don't display the same number if they are connected together. The reason is that each digit has a seperate return path[which I refer to as ground], and "only one digit return path is open[circuit completed] at one time. Although it appears that all digits are lit simultaneously, only one digit is on at any instant in time. Each digit is being turned on and off so rapidly that they appear to be on at the same time; something like a moving picture affect."

Otherwise, you would need seven "feed" paths for each digit, seven grounds paths for each digit and an ungodly number of connections at the decoder. With this elegent solution only 7 "Feed" paths are needed for the seven segments, and the four ground connections for the four digits - in a four digit display. Only 7 feed connections at the decoder and 4 connections for driving the ground conection. This is why early Pulsars have seven driver transistors.....later ones used four because the process was changed to alternate the grounds being turned on and off, rather than the "feeds".

The Calcupen is set up the same way....although, there are more ground connections since there are more digits.
http://www.retroleds.com - Sales of vintage LED, LCD, analog watches, parts and gadgets - repair tutorials & tips
Nov. 2022 - back in business!! BItter divorce is in home stretch, come grabs some great deals, I had to open the safe . . . damn attorneys. piss.
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767Geoff

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: calcupen?

Post11 Feb 2008, 22:38

Well said and quoted, problem is that the LED circuit board is covered, bonded in two layers and I could not track which solder joint was not connected.

Having repaired quite a few Summit Calculators I knew it had to be the common for the segment that had dropped out. Unfortunately it is not easily traceable. So, for the heck of it and to circumvent another tear down I soldered all the points and then cleaned as much of the circuit as I could reach.

The result is that the entire display works and I know there are no cold solder joints left on the display. I realize this is a hit and miss procedure but it worked!
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Re: SUCCESS

Post11 Feb 2008, 23:46

767Geoff wrote:I will be taking photos of the dis-assembled calcupen including some hints. I am in the process of cleaning the contact cement off the top shell and the pen, smoothing out wrinkles in the top cover, cleaning contacts and allowing the electronics to dry....
Congratulations on successful repair :-D
Can't wait to see the photos, I always wanted to know a Calcupen's inside :-)
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767Geoff

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PHOTOS ;-)

Post12 Feb 2008, 01:50

Here are the promised photos of the restoration.

The pen comes of course complete and together, stating the obvious here! It brings up a good point, how is it assembled; glue, screws, clamps, clips, pressure fit.....

Not knowing the answers and not finding any info I went with the glued and screwed scenario. At first I thought the Pen control nib was pressed and glued in position so I gently started prying it out. BIG mistake, it is actually held in place by two tiny screws. I managed to destroy the threaded plastic hole on one before realizing my mistake. This however led to the revelation that the top keyboard shell must have been applied after as it covers the screws.

I heated the top shell gently and found that an exacto knife would slide in between the top shell and the main pen body. Carefully I worked the knife along the whole seam connection the two parts. I also applied a little laqueur thinner with a fine brush which help separate the glue. Use it sparingly as you don't want it on the plastic parts. Just apply the laquer along the seam only!

Once the top shell was removed I applied some paint remover using a small artist brush on the inside lip of the top shell and removed all the excess glue. Once the glue was removed I placed the top shell on an extremely flat surface on a piece of paper. I then, using a rounded spoon handle edge, rubbed the inside lid applying pressure to smooth out the occasional ding the exacto knife made while loosening the top shell from the main body.


This photo shows the top shell removed and can be used as a disassembly or assembly reference:

Image

The offending screws which are completely invisible with the top shell in place:

Image

Follow the directions for sliding in or out of the main pen shell as you could damage the connections between the LED section and main keyboard:

Image

The module:

Image

The solder joints:

Image

Testing; "Its' alive"

Image

Closeup of the display now fixed:

Image

Cut some foam inserts to replace the original of which most had turned to dust:

Image

Dry assembled to make sure all parts fit, as a prelude to gluing. Now to gluing, what to use, crazy glue for metal, epoxy, contact cement etc

Image

I am not partial to the contact cement as it is to thick when cured and the seam would be visible. Epoxy seems the way to go at the moment but I would like a liquid glue that can seep into the seam as opposed to applying the glue with a brush like epoxy. Also have to figure away two pressure the to shells together, probably tape of some kind.

Any ideas on the glue let me know.

Cheers, Geoff
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Re: calcupen?

Post19 Jan 2023, 02:51

Thanks so much for the post Geoff. My CalcuPen started giving me problems where the buttons wouldn't respond unless I applied heat to the pen. Did the same and reheated the display solder points and wholla, it works like a charm... saved me $$$ from having to buy another one!

Regards,
Robert
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Re: calcupen?

Post19 Jan 2023, 20:49

By the way, to make the calculator serviceable again, I used 3M double stick adhesive tape to put the top cover back. I just installed a strip along the entire edge on both sides after cleaning off the old glue. Now if I need to service it again I can easily remove it in the same matter with an Xacto blade or razor blade w/o possibly damaging the cover.

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