HP-65 card motor screws

[Kees Bouw]

Hi All,

Last week I could hear a small object rolling around in my HP-65... it turned out to be one of the two screws of the card motor. I think this may have been caused by vibrations from the running motor. However, if I fasten the screw too tight, reading and writing is no longer reliable. Can anyone confirm that the position of the screws can be critical, and has anyone found a way to fix the screw (some kind of lacquer perhaps) so it does not come loose? I am quite new to restoring HP calculators, so any help will be appreciated. Another question: does a HP-65 Service Manual exist and where can I find a PDF version?

Many thanks in advance,

Kees.

[aj04062]

Use a very small drop of BLUE (not RED) Loctite on the screws and they will NOT get loose.

[Kees Bouw]

Quote:

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Use a very small drop of BLUE (not RED) Loctite on the screws and they will NOT get loose.

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Thank you for your response! Can you be a little bit more specific about which type of Loctite to use? On amazon.co.uk there are 649 Loctite products in the DIY department :-) The "Loctite 243 Lock 'n' Seal Fast Acting Thread Lock and Sealant 3ml" seems to be appropriate, but that's RED. The BLUE ones are mostly some form of superglue, is that what you mean?

[Ethan Conner]

Loctite "blue 242" threadlocker.

[Kees Bouw]

Quote:

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Loctite "blue 242" threadlocker.

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Loctite 242 and 243 appear to be the same stuff, judging by the specifications. The confusion about the colours is probably caused by the fact that (both 242 and 243) are in a RED bottle while the substance itself is BLUE.

[Ethan Conner]

I'll agree with you the packaging color is a mistake. I actually have a tube of 242 and the packaging is blue, of course i bought it five years ago. Trust me on this they may appear to be close in the spec but the red doesn't have near the holding power of the blue. I highly recommend the blue for your application unless you just like tinkering and want to go in often and reset hardware. :)

[Kees Bouw]

This is the one, right? I can't find it on amazon.co.uk but it is on amazon.com.

[Ethan Conner]

Yes that is what you want. I use it on places where there is something rotating or a pivot point and it works very good.

[Kees Bouw]

Additional info received from Henkel Ltd., UK:

"The product is just called Loctite 242, the blue refers to the products colour. In America they often refer to the colours of the product as the numbers are a bit tricky. Loctite 243 is an improved version of 242 so you might find this easier to find."

[Raymond Del Tondo]

It's Not the Position of the screw as such, but the movement space at the ends of the motor axis. If the screws are too tight, the pressure against the ball bearing on the external side of the axis may be too high, and thus the motor movement is out of tolerance.

Ray

[Kees Bouw]

Quote:

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It's Not the Position of the screw as such, but the movement space at the ends of the motor axis. If the screws are too tight, the pressure against the ball bearing on the external side of the axis may be too high, and thus the motor movement is out of tolerance.

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Thank you for your response. That really helps to understand the problem. I wonder how it was done in the factory, and in repair shops at the time. There must be people still around who worked there and know exactly how it is supposed to be done! What also puzzles me is that no-one has ever seen a HP-65 Service Manual. Did it not exist, is it very rare, was it impossible to scan into a pdf document, what is going on with this. For most other calculators there is a Service Manual, so why not for the HP-65?