old & rare? HP35:Help needed to repair

[isanchez]

Hi all,

I want to show you a new HP35 I have recently acquired, here in Spain.
It looks like one of the first hp35 (not red dot, of course), made in Singapore, with serial 1143 S 3965. The back sticker is in German. Nr 5 key with raised dot.
It comes with hard case and a (rare?) charger (only seen before in a red dot auction, searching in the Internet), the reference number is HP 00035-70001
It is in bad state, mainly dirty and many traces of corrosion...I am really willing to start working with it!
It does not work...for the moment!

I just wanted to share it with you...maybe you can add something...

I enclose some pictures for you
ADDED: I have opened it and made some additional pictures of the inside. You can find them here: https://photos.app.goo.gl/96n6BqFy3CHpiGYZ2

Kind regards

And Happy New Year!!

Ignacio

[Didier Lachieze]

Thanks for sharing. This is indeed one of the very early Singapore made HP 35. This is a nice find, they are pretty rare. I've seen a couple of power adapters like yours, they seem to have been quickly replaced in Europe by the HP 82010A.
If you succeed in repairing it, I would be interested to know if this unit has the 2.02 ln e^x bug

[Dieter]

(01-03-2018 11:42 AM)isanchez Wrote:  The back sticker is in German.

Looking at the back label there are two things that catch my eye:

First, the stack diagram at the bottom has the X and Y lines reversed. And in the third (or fourth) column there is an "E" instead of a 3. Are these errors also present in other languages? Or even in later German labels?

Then the instructions seem to suggest that STO does not enable stack lift, just like CLX and ENTER. Is this really true for the 35s?

Dieter

[isanchez]

Hi Dieter,
thanks for your contribution!
Concerning the label: looking at the picture shown in the HPMuseum, for the German label, it does not show the errors detected by you. Also, for Danish and Finnish labels, both mistakes are present. Seems to be an early version with a couple of errors.

Yesterday I had the opportunity to open it and make a deep clean.
The charger does work fine.
The calculator now turns on but shows nonsense characters.

I give you a description of the behaviour:
-When I turn it on, most of the times it shows three "zeroes" in the three extreme right (yes extreme right) display. Sometimes this behaviour changes but follows the same pattern)
-Some other figures (zeroes) are shown very dim.(mainly, the six ones starting from the left, but not always)
- When any number is pressed, it is shown in these three characters (and also in the dimmed).
-When I press "clx" it comes back to zeroes.
-When I press e^x it shows ones.
-ln0 shows blinking characters (error message)
-No apparent answer when "enter" is pressed.

I can make any test for you to give a clue about the problem.

I feel the board is Ok (it looked pristine) and could be either the display cathode or the anode...any idea? Is it possible to get a spare from an HP45?

Thanks and kind regards

Ignacio

[Didier Lachieze]

(01-04-2018 08:17 AM)Dieter Wrote:  Looking at the back label there are two things that catch my eye:

First, the stack diagram at the bottom has the X and Y lines reversed. And in the third (or fourth) column there is an "E" instead of a 3. Are these errors also present in other languages? Or even in later German labels?

Good catch ! Effectively the X and Y lines reversed and “E” instead of 3 in the third (or fourth) column are present in the early Singapore labels for several non-English languages (verified for German, Dutch, Italian, French and Spanish). These issues have been fixed in the second revision of the Singapore labels (German label ref changed from 00035-80013 to 00035-80040).

(01-04-2018 08:17 AM)Dieter Wrote:  Then the instructions seem to suggest that STO does not enable stack lift, just like CLX and ENTER. Is this really true for the 35s?

Yes, if you type: 25 STO 4 , 25 is stored in the memory register, then 4 replaces 25 in the X register.
This is also mentioned in the HP-35 manual:

Quote:MORE MEMORY
Your HP-35 has an additional memory register for storing constants. It is not affected by computations.
However, a keyboard entry or RCL immediately following STO does not raise the stack.

@Ignacio, unfortunately I've no clue on the issue with your HP-35, however you should be able to test your CPU board in an HP-45 to check that it is working correctly. If yes, then you will have to investigate the keyboard/display board of your HP-35 and eventually replace it or the display drivers (as far as I know you should be able to use a board from an HP-45 if you have one available).

[isanchez]

Dear Didier and Dieter,

thanks for your helpful comments.

I have installed the board in an HP45 and it WORKS perfect

Regarding the BUG (2.02 ln e^x=2): YES, it has the bug.

As the board works, seems that the problem is located in the display board. I can get a 45 as donor. I would like to keep the 35 original board as much as posible (not fully replacing it by the 45 one, as a first approach to the solution)

I am not sure where to start: by the cathode or the anode? Do you have any idea, taking into account the calculator behaviour?.

Seems that the cathode is fully compatible with HP45, but not the anode, but not sure about this.

Again, thanks for your help!

Kind regards

Ignacio

[Harald]

It is probably the anode driver that has failed. As far as I know all the drivers are compatible, so you could replace just the broken one. Depending on your soldering skills, you could replace just the single chip. But if you are not 100% sure you will manage to do the swap without breaking anything, I'd recomend you swap the whole keyboard/display PCB.

Good luck!

[AndiGer]

Just concerning the German back label:
My 1302S also has the 00035-00013 label as Ignazio's.
Can't tell it is a later version 2 or a version 3 as it misses the front label and does not have the raised dot on the 5.
Andi

[isanchez]

Hi again,

just confirm another HP35 from Singapour, sn 1143S 8596, with back label in Spanish and both errors present (Y, X swapped & E, instead of 3).
I believe it does not have the 2.02 bug, but I can check it.
Regards

Ignacio