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My new(ish) HP-45
01-13-2020, 10:39 AM (This post was last modified: 01-13-2020 10:41 AM by teenix.)
Post: #1
My new(ish) HP-45
Hi all,

A little while back I got a HP-45 from TAS. The ad said it was dead but it looked tidy and I got it for $45.00.

On inspection it wasn't dead but had some half dead displays. I had another old 45 that Harald gave me to develop the MultiCalc on which had good displays so I transplanted the keyboard. It needed half a dozen or so broken CPU to Keyboard pins replaced which came from the new keyboard.

I scrubbed up a powdery blue battery terminal and gave it a polish with nanna's old toothpaste and looks almost as good as new.

The back label was pristine but after reassembly I managed to get most of the wrinkles out and I left out the 2 screws for future work. I don't think they are really needed.

It is missing a battery cover retainer/rubber foot but one will show up one day.

So this finally takes me back to my school days when nostalgia got me started on this journey into HP calculators.

[Image: HP45.jpg]

cheers

Tony
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01-13-2020, 10:54 AM
Post: #2
RE: My new(ish) HP-45
I just got two HP-45s and after some TLC they are now functioning great. Fortunately mine were in good overall condition and only needed some keyboard cleaning to eliminate keys not registering or bouncing.

I belive the HP-45 is a great calculator for most basic needs when programming is not required. I am particulrly fond of the shifted funcions being printed on the faceplate instead on the keys themselves, which make them easier to read.


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01-13-2020, 02:35 PM
Post: #3
RE: My new(ish) HP-45
Nice restoration Tony!

I've picked up a couple 45's myself on the Bay in recent years ($25-30/ea, they are plentiful) and though both are fully working they need serious keyboard cleaning. This great post has motivated me to pull them out and get them into the project queue. I've held off since I didn't want to spoil the rear labels, but this nice job shows that it can be done w/o resulting in the oft-seen 'folded corners' syndrome.

Thanks for sharing this motivational post.

--Bob Prosperi
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01-13-2020, 02:42 PM
Post: #4
RE: My new(ish) HP-45
The 45 is often available for a steal. In objective terms, it's better than the 35 in a number of respects and worse in none (except being evolutionary and not revolutionary), AND you can often find them for <=$50. What's not to like?. I've got a couple myself that I picked up as "opportunistic deals" and both are great.
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01-13-2020, 09:42 PM
Post: #5
RE: My new(ish) HP-45
(01-13-2020 02:35 PM)rprosperi Wrote:  Nice restoration Tony!

I've picked up a couple 45's myself on the Bay in recent years ($25-30/ea, they are plentiful) and though both are fully working they need serious keyboard cleaning. This great post has motivated me to pull them out and get them into the project queue. I've held off since I didn't want to spoil the rear labels, but this nice job shows that it can be done w/o resulting in the oft-seen 'folded corners' syndrome.

Thanks for sharing this motivational post.

I don't know if it has been mentioned before, (most likely has), but I am careful not to bend the label, resulting in a crease, just gently tease it up.

On replacement, I rub it down with light finger pressure trying not to push the label into the screw hole.

Then to finish, place some paper, like a post-it note, over the label and a bit of the surrounding plastic.

I then use the 1" wide flat end of a steel ruler angled at 45 degrees or so, and drag it over the paper with a little pressure towards the corner of the label. The point contact from the ruler edge seems to iron out any small creases and ripples. The tiny step in the plastic label area serves as a guide to drag the ruler along.

The ruler cannot have any damaged edges or razor sharp corners or you risk scoring the label and ripping the paper. Fine emery paper could take the edge off it.

cheers

Tony
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01-13-2020, 11:00 PM
Post: #6
RE: My new(ish) HP-45
Thanks for these techniques and tips Tony, very helpful suggestions.

I planned to use a heat gun to soften the label adhesive before pulling it back. I've heard several folks (some that do this all the time) suggest it's best to remove the label fully, clean the old adhesive from the label and the calc. body, and then add new sheet adhesive to mount the label. Either way, I'm not putting the 2 screws underneath back in; I don't know if I'll ever need to open them again (hopefully someone else will be doing it in another 45 years) but there's surely no need to have 6 screws, 4 will do just fine.

Thanks.

--Bob Prosperi
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01-13-2020, 11:48 PM
Post: #7
RE: My new(ish) HP-45
(01-13-2020 11:00 PM)rprosperi Wrote:  Thanks for these techniques and tips Tony, very helpful suggestions.

I planned to use a heat gun to soften the label adhesive before pulling it back. I've heard several folks (some that do this all the time) suggest it's best to remove the label fully, clean the old adhesive from the label and the calc. body, and then add new sheet adhesive to mount the label. Either way, I'm not putting the 2 screws underneath back in; I don't know if I'll ever need to open them again (hopefully someone else will be doing it in another 45 years) but there's surely no need to have 6 screws, 4 will do just fine.

Thanks.

I think I remember something mentioned about 3M adhesives, but it eludes me.

Do you know a suitable kind that will still allow removal?

cheers

Tony
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01-14-2020, 12:03 AM (This post was last modified: 01-14-2020 12:05 AM by teenix.)
Post: #8
RE: My new(ish) HP-45
Hi all,

I was just removing some bubble displays to swap around for good ones. This proved to be a bit more difficult than I thought as the manufacturing process put small blobs of solder on the display pins on the upper surface of the board. I have an electric de-soldering tool but it had difficulty removing this solder as did de-solder braid.

LEDs don't like a lot of heat, so to help keep the display innards cool I attached a spring loaded binder clip over the pins to act as a heat sink. This was warming up during the process so hopefully it was absorbing the unwanted heat.

The red plastic is a bit softer than I thought and the binder clip slipped off and the sharp corner scuffed over one of the display lenses and gouged it making the digit look like it had distorted LED segments. Murphy is still around so it had to be a good display.

Anyway due to the rarity of these today, I got a fine needle nose file and gave it a clean up as best I could, then out with the old toothpaste again to polish the surface and it came up pretty good.

Its hard to pick the damaged one - 2nd from left:-)

cheers

Tony


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01-14-2020, 02:59 AM
Post: #9
RE: My new(ish) HP-45
(01-13-2020 11:48 PM)teenix Wrote:  
(01-13-2020 11:00 PM)rprosperi Wrote:  Thanks for these techniques and tips Tony, very helpful suggestions.

I planned to use a heat gun to soften the label adhesive before pulling it back. I've heard several folks (some that do this all the time) suggest it's best to remove the label fully, clean the old adhesive from the label and the calc. body, and then add new sheet adhesive to mount the label. Either way, I'm not putting the 2 screws underneath back in; I don't know if I'll ever need to open them again (hopefully someone else will be doing it in another 45 years) but there's surely no need to have 6 screws, 4 will do just fine.

Thanks.

I think I remember something mentioned about 3M adhesives, but it eludes me.

Do you know a suitable kind that will still allow removal?

cheers

Tony

Nah, I wish I did. I've found that if an adhesive is good enough to 'permanently' attach a label, it will not be easily removable. But I've also found using a heat gun to be the best means to loosen adhesives, though you have to be really careful to not melt the plastic underneath or damage anything inside. The key is to keep the heat gun constantly moving while continuously trying to pry/pull off the label, and never, ever use a hair dryer.

--Bob Prosperi
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01-14-2020, 03:18 AM
Post: #10
RE: My new(ish) HP-45
Use a hair dryer for releasing the adhesive. Much milder on the case and less of a chance of melting it.

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01-14-2020, 03:22 AM
Post: #11
RE: My new(ish) HP-45
Check out this link

HP 45 resto
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01-14-2020, 03:52 AM
Post: #12
RE: My new(ish) HP-45
Sorry Geoff, we'll just have to agree to disagree about using hair dryers.

Every person that has used them that I know (except you...) has damaged the device due to the excessive heat and lack of control. Of course heat is just heat, so it's not the dryer per se that damages things, it's just a ball-peen hammer when sometimes a tack hammer is needed. You obviously have tons of skill and experience so it's no surprise you had success, but I'd hate for people new to repairs to think that's the best tool to use.

The kind of heat gun used for shrink wrap (which I assume Tony has) is IMHO better suited for things like label removal.

You've no idea how many laptops, calculators, tablets and phones, etc. I've seen in varying stages of melt-down, since hair dryers were "handy" and "available".

--Bob Prosperi
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01-14-2020, 04:14 AM (This post was last modified: 01-14-2020 04:15 AM by Geoff Quickfall.)
Post: #13
RE: My new(ish) HP-45
Not to worry, i thought you meant the same heat gun I have for paint removal and working on the 73 Celica. It is either on or off!

So a heat gun with fine heat control would be fine! I should have been more specific. I have a hair dryer with low medium and hot and I only use the low setting.

Happy new year!
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01-14-2020, 04:17 AM
Post: #14
RE: My new(ish) HP-45
(01-14-2020 03:52 AM)rprosperi Wrote:  Sorry Geoff, we'll just have to agree to disagree about using hair dryers.

Every person that has used them that I know (except you...) has damaged the device due to the excessive heat and lack of control. Of course heat is just heat, so it's not the dryer per se that damages things, it's just a ball-peen hammer when sometimes a tack hammer is needed. You obviously have tons of skill and experience so it's no surprise you had success, but I'd hate for people new to repairs to think that's the best tool to use.

The kind of heat gun used for shrink wrap (which I assume Tony has) is IMHO better suited for things like label removal.

You've no idea how many laptops, calculators, tablets and phones, etc. I've seen in varying stages of melt-down, since hair dryers were "handy" and "available".

Hi Bob,

I used the "handy" hair dryer but only on a moderate setting and I just made sure nothing was getting too hot. I actually keep my thumb under the airflow to feel what is happening. Unfortunately, as you say, it is easy to over do things with heat and once the damage is done there's usually no going back.

PS - I fired up the repaired display after its cut and polish and it looks great. Smells nice and minty as well :-)

cheers

Tony
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01-14-2020, 05:16 AM
Post: #15
RE: My new(ish) HP-45
Tony

Are you going to add the quartz crystal to the timing circuit for an accurate timer?

Did that to mine including the enter key mod to allow for a two finger push to activate versus the three finger push.

Geoff
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01-14-2020, 06:09 AM (This post was last modified: 01-14-2020 06:10 AM by teenix.)
Post: #16
RE: My new(ish) HP-45
(01-14-2020 05:16 AM)Geoff Quickfall Wrote:  Tony

Are you going to add the quartz crystal to the timing circuit for an accurate timer?

Did that to mine including the enter key mod to allow for a two finger push to activate versus the three finger push.

Geoff

Hi Geoff,

You never know :-)

I'm not sure where to get the crystal as it has an odd frequency.

I take it just add another bump under the enter key for the extra contact.

cheers

Tony
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01-14-2020, 06:37 AM
Post: #17
RE: My new(ish) HP-45
(01-14-2020 03:22 AM)Geoff Quickfall Wrote:  Check out this link

HP 45 resto

All of this soon available on THE Book!

;)

Greetings,
    Massimo

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01-14-2020, 09:35 AM
Post: #18
RE: My new(ish) HP-45
Two answers!

It’s already in the book and 2nd the crystal is the same freq as the HP55 so you need to find a donor 55.

And yes the book is coming. I know I know but...
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01-14-2020, 11:56 AM
Post: #19
RE: My new(ish) HP-45
Details of the crystal mod are linked from the museum front page.
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01-14-2020, 02:16 PM
Post: #20
RE: My new(ish) HP-45
(01-14-2020 04:17 AM)teenix Wrote:  I used the "handy" hair dryer but only on a moderate setting and I just made sure nothing was getting too hot. I actually keep my thumb under the airflow to feel what is happening. Unfortunately, as you say, it is easy to over do things with heat and once the damage is done there's usually no going back.

PS - I fired up the repaired display after its cut and polish and it looks great. Smells nice and minty as well :-)

cheers

Tony

Using your fingers is the right technique. If the thing you are heating is too hot to touch, you will almost certainly damage it.

You stole my line - I was preparing to ask if the LED smelled minty fresh!

I'd also like to hear the technique you used for polishing with toothpaste and which brand had the right amount/type of fine abrasive; toothpaste ads for exotic flavors and vague guarantees to whiten are easy to find, but abrasion level specs. not so much.

--Bob Prosperi
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