HP 34C repair


Hello! i'm trying to repair a hp34c with the flat connection cable broken 'cause of the corrosion (battery leakage) I tried to repair it witha flat cable but maybe I wrong something (it still doesn't work, and I hope to have no done more damages)
Anyhow I've found a previous topic and a reply by Jon where he told to have picture showing theconnections. I ask him, please, or anybody knows the pictures or istructions to identify the connections, where are the three points to connect. Thank-you

here's the topic link


Please take a look at the pictures in this photobucket album (courtesy of Luiz C. Vieira, a contributor to this forum).


Thank-you Gerson, and thank-you Luiz, great picture!
I'll keep you informed of the repair, thank-you a lot!

Edited: 29 Nov 2009, 5:05 p.m.


conections restored, but calculator still not shows signs of life, maybe corrosion has created other problems. by a first wiev, nothing appears..................


this article may help you. In bocca al lupo! :-)


Thank-you Gerson, now I go to sleep (1 o'clock in the mornig, today I'll read it carefully, Stay tuned an THANK YOU AGAIN


I repaired my 34c using following these instructions with great success.

- Pauli


Hey, Gerson; thank you for your reminding! I appreciate! Nothing else pays better than the satisfaction of helping someone in need. Unfortunately not all people think this way...

I would like to add another link, to this picture, because chances are that Aurélio will have to replace the flex circuit. I have already done this replacement successfully at least two times.

Best regards and success, Aurelio!



Thank you Luiz for your help! I have quite a good new: now the calculator at least wake up!
When I switch on on power up and shows me something in the display:
most of the segments don't light (Don't know if it is a problem of display) but it try tho show: "program error" , the message which usually appears after you replace the battery pacK, I tried to key each number of the keyboad to get something, but what the display shows is irregular and nosense, partial characcers, blanks...I don't know if this dipends on the display, ton he flat cable, on the other components, or on the blue oxidation on the pin of the ICs.
If Iwould like to replace the flex circuit, do you have a picture of the other side? I mean the other end of the flat


Hi, Aurélio;

of course I can provide other pictures, just gimme a couple of hours (if I do not find the pictures, I'll take new ones...).

One question: can you tell if your calculator has the IC´s soldered in place or if they are just assembled over a flex-circuit surface (solderless-type). These solderelss units usually have this problem with the LED display, and it is just bad contact.

If you need further info or images, just let me know. And as soon as I have the picture I´ll post again (have no Spice opened now, and I do not remember which HP38 is the one with the flat cable...)


Luiz (Brazil)


Hi Luiz, now I'm quite far from my home and I'll be away from the calculator till to friday, anyway as I can remember the ICs the BIG one and the three small, ROMS I think, are soldered on the printed circuits (I have to check it better). I don't undrstand why the spices have only one board (circuits+keyboard toghether) I could not see the rear of the ICs (when usually the pin are soldered'cause of that)

Pictures and all your tips and help are welcome, of course, THANK-YOU a lot

Edited: 1 Dec 2009, 7:30 a.m.


Hi Luiz!
Just reopened the calculator and seen that the ICs are mountend on a board, but the pins don't pass though the board (I don't se any hole. It seems anyhow that somebody (maybe the previous owner) made any soldering point 'cause I see that some pin have been touched.
There is a sign o The big IC It seems that somebody touched it with a soldering iron. The rear of the board have the keyboard contacts. This is not separated as in the woodstocks......On this surface there is a plastic sheet with the other side of the contact..........

Edited: 5 Dec 2009, 11:40 a.m.


Hi, Aurélio;

please, see if your calculator looks like this one:

Details of the HP38E chips alignment

Although it is an HP38E, the HP34C has the same arrangement. The IC´s are soldered directly over the conductive tracks (a bit thicker there) so they do not pass through the PCB.

I'll take a picture (the one I promised I would... sorry!) showing the contacts and post it here later, OK? In the meantime, I tnink you'd like to have a look here, because Alberto Fenini took great pictures of his HP38E, and the last ones show the battery contacts. The same for the HP34C.

'I'll be back!'

Luiz (Brazil)


Thank-you Luiz the picture matches, it's the same kind of PCB.
Compliments to alberto for the picture and the work he has done!


Hello! Any news about the connections to replace?
More I look at this calculator and more I understand that somebody tried to repair already it, I see infact a lot of remade soldering points 8expecially on the pins of the ICs, I don'nt know if this is a good or a bad detail...........


Hello, Aurelio;

I completely missed the picture I promised... Sorry!

In the meantime, can you add a picture of yours? Just for us to see what you see.


Luiz (Brasil)


Hello and merry Christmas!
here pics of my 34c


Hello, Aurelio;

I completely missed the picture I promised... Sorry!

In the meantime, can you add a picture of yours? Just for us to see what you see.


Luiz (Brasil)

Hi Luiz, Hi all, any news for me? thankyou


Hi, Aurelio;

I sent you an e-mail; did you get it?

Luiz (Brazil)


HI Luiz, just now I've replayed, thank-you

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