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My First Classic
08-21-2018, 02:35 AM
Post: #1
My First Classic
My apologies if it isn’t the most scintillating topic for a new thread but I’m pretty excited about it. I am now the proud owner of an HP 45 - my first classic!

It’s a little rough around the edges and could use a bit of cleaning but I want to be careful and not do anything to harm it. It came with a rebuilt battery pack, the power supply and the handbook and it works perfectly.

Any thoughts on how long to let it charge and how best to clean it up would be appreciated.

Thanks,

Mike
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08-21-2018, 04:03 AM
Post: #2
RE: My First Classic
Welcome to the dark side.
Or is that light since they've got LEDs?

Pauli
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08-21-2018, 06:35 AM
Post: #3
RE: My First Classic
(08-21-2018 04:03 AM)Paul Dale Wrote:  Welcome to the dark side.
Or is that light since they've got LEDs?

Pauli

Of course it is the bright, red, side.

Greetings,
    Massimo

-+×÷ ↔ left is right and right is wrong
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08-21-2018, 08:32 AM
Post: #4
RE: My First Classic
(08-21-2018 02:35 AM)xmehq Wrote:  I am now the proud owner of an HP 45 - my first classic!

Any thoughts on how long to let it charge and how best to clean it up would be appreciated.

I never managed to get a 45.
Although i own a 25, a 35, and once i had a 55 and a 67 that i let go in a momentary lapse of reason. Still banging my head against the wall for that.

Having worked professionally as a HP distributor in the late 70's in the repair shop, and after that as a collector hobby since the late 2000, i have destroyed a few of these models while trying to improve them.
This is my shortlist of things to NOT do (exceptions may apply for specific models but better to be safe than sorry):

- Cleaning the keyboard and face plate with agressive or even alcohol based products. This is the way to have the labels removed or just faded away if you are lucky.
Usually i dismantle the unit piece by piece (this is a hobby after all) and then the individual components can be cleaned in full. I use warm water and hand dish detergent and a soft brush for everything except the electronics here i use isopropyl alchool.

- Charging the battery inside the calculator using the original HP charger while at the same time you use the calculator.
It is a matter of time until you have the calculator fried when the battery makes a poor contact due to oxidation / dry electrolysis causing the internal circuits to receive unregulated power supply (this only applies to models where the charger plug uses two pins).

I am sure the many experts here will add more details and help on these subjects.

Jose Mesquita
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08-21-2018, 08:34 AM
Post: #5
RE: My First Classic
Nice one Smile

I have one of those, too, but I need to find time to dismantle it and clean the keyboard up. It's bouncing a lot and some keys don't respond well at all.

My first `classic`, however, was a HP-35 in perfect working order. No "big bug" in mine, just the classic \(e^{ln(2.02)}\) bug.
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08-21-2018, 09:32 AM
Post: #6
RE: My First Classic
(08-21-2018 08:32 AM)jebem Wrote:  - Charging the battery inside the calculator using the original HP charger while at the same time you use the calculator.
It is a matter of time until you have the calculator fried when the battery makes a poor contact due to oxidation / dry electrolysis causing the internal circuits to receive unregulated power supply (this only applies to models where the charger plug uses two pins).

I am sure the many experts here will add more details and help on these subjects.

This is very good advice for most calculators, especailly woodstocks and spices. But the classics, with the exeption of the 65, do not have anything other than the charger connected to the battery. When the charger is unpluged, a bridge at the connector connects the battery to the calculator circuit. When the charger is plugged in, that bridge is opened.
So it is fine to charge the batteries in the calculator and even use it without a battery installed.

Cheers,
Harald
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08-21-2018, 02:18 PM (This post was last modified: 08-21-2018 02:22 PM by sasa.)
Post: #7
RE: My First Classic
(08-21-2018 08:32 AM)jebem Wrote:  - Cleaning the keyboard and face plate with agressive or even alcohol based products. This is the way to have the labels removed or just faded away if you are lucky.

Interesting. Do you know what exact paint (chemistry) and process was used to make labels on HP calculators in early 70s?

Many images shows they fade out after long usage, caused probably by oil from skin or a bit aggressive rubbing, especially around On/Off switch.
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08-21-2018, 02:40 PM
Post: #8
RE: My First Classic
Pauli and Massimo - I think it may be a little of both! I already feel like it whispers to me "now, just find a 35 and 55 to keep me company." :-)

Jose and Harald - thank you for the suggestions and information. Jose, a little digging turned up this thread about your HP 35 which I have bookmarked for reference. http://www.hpmuseum.org/forum/thread-2177.html

grsbanks - Fortunately, the keyboard on my example seems to be functioning well but it could use a little exterior clean-up.

On the topic of the keyboard, it's interesting comparing the feel of the keyboard to some of my "newer" calculators (15c and 41cv). As much as I like using the latter calculators, there really is a substantial difference in the feel of the keypresses that I like on the 45 - it seems much more "certain" if that makes sense.
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08-21-2018, 02:49 PM
Post: #9
RE: My First Classic
(08-21-2018 02:40 PM)xmehq Wrote:  Jose and Harald - thank you for the suggestions and information. Jose, a little digging turned up this thread about your HP 35 which I have bookmarked for reference. http://www.hpmuseum.org/forum/thread-2177.html

Thanks for digging that thread out! I now have a better idea of what to expect when I finally get round to disassembling my HP-45 Smile
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08-21-2018, 03:16 PM
Post: #10
RE: My First Classic
(08-21-2018 02:35 AM)xmehq Wrote:  My apologies if it isn’t the most scintillating topic for a new thread but I’m pretty excited about it. I am now the proud owner of an HP 45 - my first classic!

It’s a little rough around the edges and could use a bit of cleaning but I want to be careful and not do anything to harm it. It came with a rebuilt battery pack, the power supply and the handbook and it works perfectly.

Any thoughts on how long to let it charge and how best to clean it up would be appreciated.

Thanks,

Mike

Ahh, memories! My first calculator was a 45. I wanted a 35 but by the time I had enough money for one (being a poor college student) the 45 was announced so I got that instead. When you open it up to clean it, you might as well install a crystal so the undocumented stopwatch functions are accurate! See here for details: http://www.hpmuseum.org/45crys.htm

Tom L
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Look who we each married!
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08-21-2018, 04:18 PM
Post: #11
RE: My First Classic
(08-21-2018 02:18 PM)sasa Wrote:  
(08-21-2018 08:32 AM)jebem Wrote:  - Cleaning the keyboard and face plate with agressive or even alcohol based products. This is the way to have the labels removed or just faded away if you are lucky.

Interesting. Do you know what exact paint (chemistry) and process was used to make labels on HP calculators in early 70s?

Many images shows they fade out after long usage, caused probably by oil from skin or a bit aggressive rubbing, especially around On/Off switch.

The labels printed on the face plate don't fade, as far as I'm aware, but they rub off very easily, and you don't need solvents for that to happen, either. I noticed this once while trying to clean the keyboard on my HP-25, when it was still new; after a bit of rubbing to remove a spot of grease between two keys, the INT label was half gone. Oops! Luckily my fingers are thin enough that I never hit the face plate by accident, and ever since I only clean the face plate by gently wiping it with a soft, dry cloth. The HP-67 and another HP-25 that I got more recently have good face plate labels, could be that they looked a bit crisper when those machines were new, but they look fine to me now as well.
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08-22-2018, 12:47 AM
Post: #12
RE: My First Classic
(08-21-2018 09:32 AM)Harald Wrote:  
(08-21-2018 08:32 AM)jebem Wrote:  - Charging the battery inside the calculator using the original HP charger while at the same time you use the calculator.
It is a matter of time until you have the calculator fried when the battery makes a poor contact due to oxidation / dry electrolysis causing the internal circuits to receive unregulated power supply (this only applies to models where the charger plug uses two pins).

I am sure the many experts here will add more details and help on these subjects.

This is very good advice for most calculators, especailly woodstocks and spices. But the classics, with the exeption of the 65, do not have anything other than the charger connected to the battery. When the charger is unpluged, a bridge at the connector connects the battery to the calculator circuit. When the charger is plugged in, that bridge is opened.
So it is fine to charge the batteries in the calculator and even use it without a battery installed.

Cheers,
Harald

This is true with the topcats as well.
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08-22-2018, 02:27 PM
Post: #13
RE: My First Classic
(08-21-2018 02:35 AM)xmehq Wrote:  Any thoughts on how long to let it charge and how best to clean it up would be appreciated.

Thanks,

Mike

Charging time will depend on the capacity of the cells in the rebuilt pack. I assume you plan to charge using the original AC adapter, correct? (No danger to the calculator as others have stated). If I recall correctly, charging time with original cells was something like 12 hours. Modern cells have double or more the capacity, so charging time will extend accordingly.

(08-21-2018 03:16 PM)toml_12953 Wrote:  Ahh, memories! My first calculator was a 45. I wanted a 35 but by the time I had enough money for one (being a poor college student) the 45 was announced so I got that instead.

I could say the exact same thing, except replace “poor college student” with “poor high school student”. To heck with saving up to buy a car, I wanted a calculator!

Dave - My mind is going - I can feel it.
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08-23-2018, 02:03 AM
Post: #14
RE: My First Classic
The battery pack doesn’t have any obvious indicator of its capacity. There is a blue label with what appears to be a stylized A and the part number 1420-0272 but my internet search for the number was inconclusive. I did see in there user handbook that charging takes about 14 hours for the original battery.

Electronics and batteries not being my forte, I was actually concerned about determining if there is a problem with leaving it plugged in for extended periods.

In any case, I’m enjoying getting to know the calculator and reading the manual. Why is it that so few products come with well-written manuals?

Anyway, thanks for the insights.
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