The HP 45 complete restoration with PICTURES!


I purchased this through ebay as a parts machine.

When it arrived I noticed the case, aside from the labels on the side was in pristine condition, almost perfect with no attempt to access the insides.

The keyboard was unresponsive on 80% of the keys, the on off switch was intermittant at best. The only way to power it up was with an adapter as the battery function seemed unservicable also.

Well, using previously posted articles in the REPAIR section of the HP museum I was able to bring this up to snuff and fully functional to boot.

Please excuse the typos on the photos. Also I usually do not reinstall the label on the back but keep it with the calculator for attachment at a later date when I am assured that I do not have to get into the calc again.

So to date the following have been restored (R) and collected (C):

HP 92(R)
HP 97(R)
HP 67(X 3, R)
HP 67(NOS still shrink wrapped in original box)
HP 25c (R)
HP 35 (R)
HP 45 (R)
HP 55 (R)
HP 41C (used in university)
HP 41CX (X 2 plus many accessories used in university)
Here are the pictures with embedded explanations:

Edited: 18 Jan 2008, 5:50 p.m. after one or more responses were posted


Good work.
¿did you take some precautions against static electricity?.
¿How did you manipulate the electronics?

Bye, ricardo


I use a grounding strap attached to the common ground at an electrical outlet and attached to a bracelet on my left arm. I am right handed!

The circuit board was removed with the strap in place and placed on a plastic ground sheet I save from computer products. The theory is that you ground the charge to the sheet before you touch the circuits.

The soldering was kept to a minimum, the power wires that attach the keyboard to the battery section.

The circuit keyboard was washed with a natural hair paintbrush and vinegar then rinsed with alcohol and blow dried on medium heat.

The label was removed after the corners were peeled back and the back case half was separated from the top or front case back. This kept the heat from the hairdier to a minimum with respect to the internal circuits.

Cheers, Geoff


Congratulations! Enjoy your new toy :)


I am thinking of doing this but the instructions at this site have confused me a bit. Does one need the choke or not?

Cheers, Geoff


Very nice! just one question (not critical just curious): you said "the label was completely removed after the back was separated" did you glue it back in? if not, why did you removed it completely?, it does not seem necessary, did it break?, in any case, good work!

Regards, Thor

Edited: 18 Jan 2008, 5:38 p.m.


To remove the back label I heated the corners with a hair dryer. To much heat can harm the internal circuit board but it is the only way I know to gain access to the screws without destroying the label.

Once the screws are exposed, I dis-assemble the calculator and am left with the bent label on the rear shell of the calc. At this point I can then heat the rest of the label and remove it.

It is then placed in a heavy vinyl envelope and rubbed with a spoon to remove the wrinkles and creases created by the removal process.

The label as you can see in this picture (which I meant to include in the above posting) is in perfect condition.

The reason to remove it is to smooth it out and curve it by rubbing so that when it is re-applied it looks as though it was never removed.

I have not however attached it to the calc as this is part of my private collection and I may need to get into the calc again for some tweeking (quartz crystal insertion for the timing circuit) and do not want to go through the label removal procedure again.

Cheers, Geoff

Edited: 18 Jan 2008, 5:52 p.m.


On units that I service, I put the label back on the case omitting the two screws under the label. The four remaining screws are more than enough to hold everything together.

Thanks go to David Smith for the idea. Where has he been? Long time no post.


Thanks Randy, nice suggestion.

All of the restoration work done here was with reference to various contributors to the HP Museum.

I have used there postings to repair my HP 67's, 97's, 92 printer and the HP 41 card readers I have.

Cheers, Geoff


Thanks for the reply, Thor


Thanks much.

It makes me fee lmore motivated to clean my (still functioning) 45!


I am thoroughly impressed, not only by the final product but also by the display of diligence and love for detail. Amazing work, stunningly beautiful end result!




any ideas about the quartz crystal would be helpful.

Cheers, Geoff

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