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My first HP-35 and a happy end
09-22-2014, 08:47 PM
Post: #1
My first HP-35 and a happy end
Today was a nice day for me!
This afternoon I collected my first HP-35 at the Post Office, and I have to share this with you:

The seller sold it for parts, as it didn't power on.
The charger cable near the 3-opin plug was tampered by someone that probably tried to repair a broken wire.

I was not expecting too much from this item, but when I measured the output of the charger, I saw to my surprise that the readings were at the wrong pins of the plug, having the 16V current and the 5V voltage sources swapped!

So I thought, surely this calculator has been beaten to death by receiving 16V to the power supply DC-DC converter.
What are the odds of these components to survive under these conditions?
Actually, a lot - The 16V are a current source to charge the battery.

Having corrected the mistake, I couldn't wait!
I used the multimeter in current mode and used its test probes as a switch, touching the switch contacts carefully while looking to the current meter... I saw 89.5mA... Yes, looks good enough so far...
And amazingly the calculator came to life on the first try!

The display gave that nice looking red color with a "0.".
I tried the classical multiply test: 12345679 ENTER 9 * -> 111111111
And just to make sure it works: 1000 log -> 3

This calculator was sealed from factory, never opened before, despite a lot of dirt in the keyboard area. So I decided to open it to do a good cleaning.
The electronics PCB is immaculate, though.

I will share better pictures later. For now I'm uploading the spontaneous shots took at the time of the troubleshooting.


[Image: SAM_7873.JPG]] [Image: SAM_7874.JPG]]

[Image: SAM_7877.JPG]] [Image: SAM_7879.JPG]]

Jose Mesquita
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09-23-2014, 11:54 AM
Post: #2
RE: My first HP-35 and a happy end
Congratulations on your good fortune. The HP-35 is surely a thing of beauty and obviously very robustly designed.

(09-22-2014 08:47 PM)jebem Wrote:  This calculator was sealed from factory, never opened before, despite a lot of dirt in the keyboard area. So I decided to open it to do a good cleaning.
The electronics PCB is immaculate, though.

Did you carefully remove the back label with heat and patience, or just poke holes to get at the screws? Which version is it? (Some experts can probably tell by looking at the circuit board and other evidence in your pictures, but I cannot.)

Dave - My mind is going - I can feel it.
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09-23-2014, 12:39 PM
Post: #3
RE: My first HP-35 and a happy end
(09-23-2014 11:54 AM)Jeff O. Wrote:  Did you carefully remove the back label with heat and patience, or just poke holes to get at the screws? Which version is it? (Some experts can probably tell by looking at the circuit board and other evidence in your pictures, but I cannot.)

Hi Jeff,
Thanks for your reply.

Well, usually I'm not a patient guy (like I should be on these nice rarities), only because I couldn't wait... although later I really regret by being like this.
So, I should have used a hair dryer, but this time I have just have used this old technique of breathing into the label while using a X-acto knife to carefully lift the label in order to access the screw holes.
I believe the label was not damaged in the removal procedures. I will see later when reassembling the unit after cleaning it.

Concerning the calculator generation, from what I've been reading, I came to the conclusion that there are 4 different generations (at least...?).
Mine should be a generation 3, made in USA yr 1973, because it already sports the "HP 35" logo in the front label, but the keyboard legends are still printed on the overlay.

I will upload full photos of the inside and outside as soon as I have time to do it.

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09-23-2014, 01:19 PM
Post: #4
RE: My first HP-35 and a happy end
To find a working HP 35 is quite a find. Very nice jebem!
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09-23-2014, 02:11 PM
Post: #5
RE: My first HP-35 and a happy end
(09-22-2014 08:47 PM)jebem Wrote:  Today was a nice day for me!
This afternoon I collected my first HP-35 at the Post Office, and I have to share this with you

May be useful - great info about HP-35 calculator on Jacques Laporte website:
http://www.jacques-laporte.org/
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09-23-2014, 02:20 PM
Post: #6
RE: My first HP-35 and a happy end
Contragulations! It must have been a rush to see that old display light up.
I have an HP 67 missing its battery and charger on my bench that I've thus far been too cautious to attempt to power up, so this story is rather inspiring.

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09-23-2014, 02:42 PM
Post: #7
RE: My first HP-35 and a happy end
My dad got his 35 in 1973. I have this beautiful calculator with it's instruction book, it's plastic carrying case, and the box it was mailed in from HP on my desk (next to my best slide rules). My dad rarely used it...it is in close to mint condition and works wonderfully on it's original power supply. I had to remove the rechargeable batteries.
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09-23-2014, 03:27 PM (This post was last modified: 09-23-2014 05:13 PM by aurelio.)
Post: #8
RE: My first HP-35 and a happy end
(09-23-2014 12:39 PM)jebem Wrote:  
(09-23-2014 11:54 AM)Jeff O. Wrote:  Did you carefully remove the back label with heat and patience, or just poke holes to get at the screws? Which version is it? (Some experts can probably tell by looking at the circuit board and other evidence in your pictures, but I cannot.)

Hi Jeff,
Thanks for your reply.

Well, usually I'm not a patient guy (like I should be on these nice rarities), only because I couldn't wait... although later I really regret by being like this.
So, I should have used a hair dryer, but this time I have just have used this old technique of breathing into the label while using a X-acto knife to carefully lift the label in order to access the screw holes.
I believe the label was not damaged in the removal procedures. I will see later when reassembling the unit after cleaning it.

Concerning the calculator generation, from what I've been reading, I came to the conclusion that there are 4 different generations (at least...?).
Mine should be a generation 3, made in USA yr 1973, because it already sports the "HP 35" logo in the front label, but the keyboard legends are still printed on the overlay.

I will upload full photos of the inside and outside as soon as I have time to do it.

I can understand your feeling Josè, 'cause now you not just own such a glorious calculator, but you are the doctor who gave it life again Smile

Share please the pics of your beauty when reassembled and... compliments renewed

The HP 35 is one of the calculator I like more, never I saw it when retailed, I was too young at that time...the HP 25c was already in the shops five years after, cheaper and programmable!!!

I have now one 2d edition, the third (french labeled) and the fourth as well. For the red dot there's still time Smile

It was the first of the classical calculator I added to my small collection and it's impressive to compare the weight of this "mother of all pocket scientific calculators" to the one of the calculator of about twenty years later (or ago) like the 42s, or even the just recalled HP 25c
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09-23-2014, 10:50 PM
Post: #9
RE: My first HP-35 and a happy end
Thank you, Eddie and Leonid for your comments and help!

Hi, W.B.Grant (William?)
The HP-67 - You have a fantastic machine!
I had one long time ago as a student, great machine, but it is much more complex than the HP-35 and that card reader requires special attention.
I'm sure the HP hardware experts can help on that if required.

Hi, lrdheat,
You are very fortunate to have one complete HP-35 in your possession!
I could only acquire the calculator, the charger (faulty on arrival) and one battery pack (faulty on arrival, case opened and original batteries replaced by someone).

Hi, Aurelio,
Thanks for your comments!
Ah, I see you are chasing the full HP-35 series for your collection.
What a fantastic hobby we have, isn't it?

Meanwhile I have cleaned the 35 keys and the power switch, by leaving them in water for a few hours, and then used soft dish detergent and a tooth brush to remove the dirt.
The top cover received the same treatment, but unfortunately the LED lens is just a little bit scratched and so far I am not in the mood to polish it.

[Image: SAM_7885.JPG]]


And as a side note concerning the previous owner:

When I was opening the HP-35 calculator back cover, I noticed a metallic label stuck to the side of the battery compartment.
This label has the following information:
"Property of Richard T. Hawkins"

A quick search in the Google machine reveals a number of people with that name.
However, just one fits the typical user profile of such machine, epoch and age, and motivation to put a professional label in their equipment:
Department of Chemistry and Biochemistry Brigham Young University, Provo, UT 84602

Searching just a bit more, I found this obituary:
A retired Brigham Young University organic chemistry professor Richard Thomas Hawkins passed from this mortal existence December 12, 2013, in Orem, Utah, at the age of 84.

And I bought this calculator less than one month ago from a large eBay seller in Salt Lake City, Utah, United States.

Too many coincidences for a random event.
I think I have found the original owner's name. May he rest in peace.
I will take good care of this nice piece of computer history for him.

[Image: SAM_7883.JPG]]

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09-24-2014, 01:18 AM (This post was last modified: 09-24-2014 01:19 AM by Mark Hardman.)
Post: #10
RE: My first HP-35 and a happy end
(09-23-2014 10:50 PM)jebem Wrote:  And as a side note concerning the previous owner:

When I was opening the HP-35 calculator back cover, I noticed a metallic label stuck to the side of the battery compartment.
This label has the following information:
"Property of Richard T. Hawkins"

A quick search in the Google machine reveals a number of people with that name.
However, just one fits the typical user profile of such machine, epoch and age, and motivation to put a professional label in their equipment:
Department of Chemistry and Biochemistry Brigham Young University, Provo, UT 84602

Searching just a bit more, I found this obituary:
A retired Brigham Young University organic chemistry professor Richard Thomas Hawkins passed from this mortal existence December 12, 2013, in Orem, Utah, at the age of 84.

And I bought this calculator less than one month ago from a large eBay seller in Salt Lake City, Utah, United States.

Too many coincidences for a random event.
I think I have found the original owner's name. May he rest in peace.
I will take good care of this nice piece of computer history for him.

It is a very small world Jose. I took Organic Chemistry from "Brother" Hawkins as an undergraduate at BYU in 1982. At the start of the semester, he was amazed that I was taking notes on my HP-75C and proudly produced his HP-35 for me to admire.

He was an excellent instructor and I remember enjoying his class.

As a side note, I severed as secretary/treasurer of the university's HP Calculator club during those years.

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09-24-2014, 08:25 AM
Post: #11
RE: My first HP-35 and a happy end
(09-24-2014 01:18 AM)Mark Hardman Wrote:  
(09-23-2014 10:50 PM)jebem Wrote:  And as a side note concerning the previous owner:

When I was opening the HP-35 calculator back cover, I noticed a metallic label stuck to the side of the battery compartment.
This label has the following information:
"Property of Richard T. Hawkins"

A quick search in the Google machine reveals a number of people with that name.
However, just one fits the typical user profile of such machine, epoch and age, and motivation to put a professional label in their equipment:
Department of Chemistry and Biochemistry Brigham Young University, Provo, UT 84602

Searching just a bit more, I found this obituary:
A retired Brigham Young University organic chemistry professor Richard Thomas Hawkins passed from this mortal existence December 12, 2013, in Orem, Utah, at the age of 84.

And I bought this calculator less than one month ago from a large eBay seller in Salt Lake City, Utah, United States.

Too many coincidences for a random event.
I think I have found the original owner's name. May he rest in peace.
I will take good care of this nice piece of computer history for him.

It is a very small world Jose. I took Organic Chemistry from "Brother" Hawkins as an undergraduate at BYU in 1982. At the start of the semester, he was amazed that I was taking notes on my HP-75C and proudly produced his HP-35 for me to admire.

He was an excellent instructor and I remember enjoying his class.

As a side note, I severed as secretary/treasurer of the university's HP Calculator club during those years.

People die and things survive
But things help people in reminding other people

And it's so interesting with the old stuff, to think about and to guess who owned it before, what's his history?
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09-24-2014, 06:30 PM
Post: #12
RE: My first HP-35 and a happy end
(09-24-2014 01:18 AM)Mark Hardman Wrote:  It is a very small world Jose. I took Organic Chemistry from "Brother" Hawkins as an undergraduate at BYU in 1982. At the start of the semester, he was amazed that I was taking notes on my HP-75C and proudly produced his HP-35 for me to admire.

He was an excellent instructor and I remember enjoying his class.

As a side note, I severed as secretary/treasurer of the university's HP Calculator club during those years.

Thank you so much for sharing your past experience related to this calculator and to Professor Hawkins, Mark! Indeed we live in a global village!
This calculator will remain with the original owner's label attached as it was originally.

As promised, here are the first batch of photos showing the calculator internals.

As you can see, my lack of patience already destroyed a perfectly good rubber foot only because I was not looking to what I was doing. Silly me. Hopefully the rubber
foot will stick back nicely.

[Image: SAM_7900.JPG] [Image: SAM_7898.JPG] [Image: SAM_7886.JPG]

[Image: SAM_7887.JPG] [Image: SAM_7888.JPG] [Image: SAM_7889.JPG]

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09-24-2014, 06:48 PM
Post: #13
RE: My first HP-35 and a happy end
(09-24-2014 08:25 AM)aurelio Wrote:  People die and things survive
But things help people in reminding other people

And it's so interesting with the old stuff, to think about and to guess who owned it before, what's his history?

Yap, perhaps what distinguish people from regular animals is that people have this ability to use their hands to make tools and build objects, modifying the planet landscape in a way that can last for centuries.

However, now that I think about this, the more technically advanced one given civilization is, the less evidence it leaves about its knowledge.
The new era of paperless storage have its dangers...

Following are the remaining photos of the calculator internals.

[Image: SAM_7892.JPG] [Image: SAM_7890.JPG] [Image: SAM_7893.JPG]

[Image: SAM_7894.JPG] [Image: SAM_7895.JPG] [Image: SAM_7896.JPG]

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09-24-2014, 07:32 PM (This post was last modified: 09-24-2014 07:35 PM by aurelio.)
Post: #14
RE: My first HP-35 and a happy end
(09-24-2014 06:48 PM)jebem Wrote:  
(09-24-2014 08:25 AM)aurelio Wrote:  People die and things survive
But things help people in reminding other people

And it's so interesting with the old stuff, to think about and to guess who owned it before, what's his history?

[OMISSIS]
The new era of paperless storage have its dangers...

Following are the remaining photos of the calculator internals.

Agree, Josè.........
Thank-you for sharing the internals pictures

Certainly, comparing these 35's boards, keyboard, circuits and connections to the ones of just a few years later (spice series I mean), it's practically unpossible for me: like to compare sky and earth

Maybe the spices represents the low cost project for scientific calculators (31c), but if Ithink to the 34c I can't believe that was made using ribbon connectors and unsoldered connection with all the related problems we quite well know.

It seems actually that the classics (expecially the 35A) were made to live forever while the others not..... Smile
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09-26-2014, 12:43 PM
Post: #15
RE: My first HP-35 and a happy end
(09-24-2014 07:32 PM)aurelio Wrote:  Certainly, comparing these 35's boards, keyboard, circuits and connections to the ones of just a few years later (spice series I mean), it's practically unpossible for me: like to compare sky and earth

Maybe the spices represents the low cost project for scientific calculators (31c), but if Ithink to the 34c I can't believe that was made using ribbon connectors and unsoldered connection with all the related problems we quite well know.

It seems actually that the classics (expecially the 35A) were made to live forever while the others not..... Smile

1+ Smile
To me, the technology used by HP in their products during the 70's was superior to most of the other manufacturers.
Ok, maybe Tektronix lab equipment was superior to the equivalent HP ones, but not by much.
Apparently economics and calculator market shrinking dictate that a calculator must be cheap to manufacture in order to be able to sell it...

But at least HP has retained the good click feel on most of their calculator's keyboards, and I salute HP for doing so.
Just look the the other calculator manufacturers... they look "cheap" to me when I put their products side by side with HP machines.

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09-26-2014, 06:00 PM (This post was last modified: 09-26-2014 07:13 PM by aurelio.)
Post: #16
RE: My first HP-35 and a happy end
(09-26-2014 12:43 PM)jebem Wrote:  
(09-24-2014 07:32 PM)aurelio Wrote:  Certainly, comparing these 35's boards, keyboard, circuits and connections to the ones of just a few years later (spice series I mean), it's practically unpossible for me: like to compare sky and earth

Maybe the spices represents the low cost project for scientific calculators (31c), but if Ithink to the 34c I can't believe that was made using ribbon connectors and unsoldered connection with all the related problems we quite well know.

It seems actually that the classics (expecially the 35A) were made to live forever while the others not..... Smile

1+ Smile
To me, the technology used by HP in their products during the 70's was superior to most of the other manufacturers.
Ok, maybe Tektronix lab equipment was superior to the equivalent HP ones, but not by much.
Apparently economics and calculator market shrinking dictate that a calculator must be cheap to manufacture in order to be able to sell it...

But at least HP has retained the good click feel on most of their calculator's keyboards, and I salute HP for doing so.
Just look the the other calculator manufacturers... they look "cheap" to me when I put their products side by side with HP machines.
For me HP is "the calculator".
Then when you drink wine, an excellent wine, water is nothing if compared.
And what you expect from a DOC (*) wine is a unique taste and the excellence that others haven't.
From it you expect always the best, but we know for wines the are good and bad seasons, but this is not under our control I think.

Never I personal opened, before joining our forum a few years ago, a calculator to see what's inside and how it works,
My father did it with the 25c, he had not schemas but he was able to test ICs and the electronics inside and his great experience with electronics at that time was helpful. I used also the spices (31 and 33) availble in mostly the radio-electronics laboratories at that time and I enjoyed them alot (expecially the 33) like my 25c but prettier (cause of the dark one colour case) and the more readable display, never I thought at their internals or at their future life....

But maybe these are all considerations of a middle age man nowadays, with homesick for the past, never in peace with himself Smile


(*) term signifying that a wine is of a certain origin and quality
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09-26-2014, 06:13 PM
Post: #17
RE: My first HP-35 and a happy end
(09-23-2014 10:50 PM)jebem Wrote:  ...
Hi, W.B.Grant (William?)
The HP-67 - You have a fantastic machine!
...

Walter, actually, but I generally answer to my middle name, Bruce.

Regards,
WBG
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09-27-2014, 10:10 AM
Post: #18
RE: My first HP-35 and a happy end
(09-26-2014 06:00 PM)aurelio Wrote:  Then when you drink wine, an excellent wine, water is nothing if compared.
And what you expect from a DOC (*) wine is a unique taste and the excellence that others haven't.
(*) term signifying that a wine is of a certain origin and quality

Here in Portugal we use the same system designation to sell our wines - DOC ("Denominação de Origem Controlada").
Most of them are good, some are excellent and others, well, have their name protected by "DOC" but they are best used as a cooking condiment.

Alright, here it is my last batch of photos of my HP-35.

It works fine, even the battery pack is almost perfect after taking about 14 hours of charging to regenerate the cells.
And the famous "exp(ln(2.02) = 2" bug is of course missing in this firmware release.

[Image: SAM_7946.JPG] [Image: SAM_7947.JPG] [Image: SAM_7948.JPG]

[Image: SAM_7949.JPG] [Image: SAM_7951.JPG] [Image: SAM_7952.JPG]

[Image: SAM_7953.JPG] [Image: SAM_7954.JPG] [Image: SAM_7955.JPG]

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09-27-2014, 11:35 AM (This post was last modified: 09-27-2014 11:45 AM by aurelio.)
Post: #19
RE: My first HP-35 and a happy end
(09-27-2014 10:10 AM)jebem Wrote:  
(09-26-2014 06:00 PM)aurelio Wrote:  Then when you drink wine, an excellent wine, water is nothing if compared.
And what you expect from a DOC (*) wine is a unique taste and the excellence that others haven't.
(*) term signifying that a wine is of a certain origin and quality

Here in Portugal we use the same system designation to sell our wines - DOC ("Denominação de Origem Controlada").
Most of them are good, some are excellent and others, well, have their name protected by "DOC" but they are best used as a cooking condiment.

Alright, here it is my last batch of photos of my HP-35.

It works fine, even the battery pack is almost perfect after taking about 14 hours of charging to regenerate the cells.
And the famous "exp(ln(2.02) = 2" bug is of course missing in this firmware release.

thank-you for sharing and compliments for your machine...it looks really very nice and well conserved, I like so much the shape of the battery springs: they look like new!!!

About wines, here in Italy too we can't say that every DOC wine is excellent or good......but you know biscuits not always come out well cooked and the cook sometimes is too lazy Smile
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