Should I bother? HP-34C in rough shape

[dm123]

Thanks Max, I will try to find it, then post it here to make sure it is legit, before buying it. I will update this thread once I power the old calculator up, as well. It's probably been over 30 years. Finger crossed

[dm123]

Hi Max, I found it here. Does this look ok? Do I have to take the old batteries out of the original metal casing, or can I just insert these batteries as is?
I have asked the seller the same.


http://www.ebay.com/itm/Battery-1000mAh-...SwzhVWs74G

[Massimo Gnerucci]

(04-19-2017 07:30 PM)dm123 Wrote:  Thanks Max, I will try to find it, then post it here to make sure it is legit, before buying it. I will update this thread once I power the old calculator up, as well. It's probably been over 30 years. Finger crossed

Look for waterhosko on eBay

[dm123]

Thanks Massimo, I will order it. Best regards, dm

[Massimo Gnerucci]

(04-19-2017 08:50 PM)dm123 Wrote:  Thanks Massimo, I will order it. Best regards, dm

These are NiMH...

[rprosperi]

Here's one:

http://www.ebay.com/itm/Hewlett-Packard-...2480179874

[dm123]

Thanks all the battery is on its way. The test will follow. I will keep you all posted.

Best regards,

dm

[dm123]

Wow, I'm trying to get the thing open, and the bottom part won't budge. I've tried everything including the dental floss Loop method. Nothing will budge it, and I don't want to crack it while opening it.

[AndiGer]

Did you try this? To my experience must apply much power, don't fear to break it.
http://www.voidware.com/calcs/spicerepair.htm
Andi

[dm123]

(04-26-2017 03:57 AM)AndiGer Wrote:  Did you try this? To my experience must apply much power, don't fear to break it.
http://www.voidware.com/calcs/spicerepair.htm
Andi

Andi, brilliant. It worked. I read about the method, but a picture is worth a thousand words.

Prior to this, I inserted my new battery from eBay (the good seller), and plugged in the ac power adapter. Not what I expected. A little red dot in the upper left corner. I know the display is good because every now and then the entire display flashes stuff, almost like it is iterating through a program. But I don't get anything more.


I opened it up and took a picture and posted it here. There was some green stuff on the power strip I cleaned up. Everything else,I'm leaving till I hear back from some experts on this thread. There is no corrosive material inside, which is good.

Do I need to simply charge the battery . I'm not sure if he shipped it out charged. Without ac, the display is dead. With ac red dot and periodic flashing of lots of digits in the display.


Here Are the pictures. Titled hp34c opened Thanks all for the help so far

https://imgur.com/gallery/pHgYz

I just added a close up of the battery/power lead connector as well

https://imgur.com/gallery/WS2uq

[AndiGer]

As there seems to be same oxidation (blue copper) on the flex cable as well:
Did you check these go thru to the electronics?

--> Cathode (upper battery contact) vs. 6th connection counted from the left of the flex cable as you look on it
--> Anode (lower battery contact) vs. 3rd connection of the flex cable counted from the left as you look on it
--> Rivet in the middle between the battery contacts to left most connection (but not so important - is cathode from charger for charging electronics AFAIK). If this one is not connected / goes thru you can not charge the batteries inside the calculator.

If all connections ok you have to disable more I guess. But yours is the soldered (therefore the more reliable) version as I can see from the pictures.

Andi

[dm123]

(04-26-2017 05:04 PM)AndiGer Wrote:  As there seems to be same oxidation (blue copper) on the flex cable as well:
Did you check these go thru to the electronics?

--> Cathode (upper battery contact) vs. 6th connection counted from the left of the flex cable as you look on it
--> Anode (lower battery contact) vs. 3rd connection of the flex cable counted from the left as you look on it
--> Rivet in the middle between the battery contacts to left most connection (but not so important - is cathode from charger for charging electronics AFAIK). If this one is not connected / goes thru you can not charge the batteries inside the calculator.

If all connections ok you have to disable more I guess. But yours is the soldered (therefore the more reliable) version as I can see from the pictures.

Andi

Hi Andi, I posted another close up. The blue copper is there as you can see. It's peeling. Can I pull it off, or,is there a recommended solvent to get it off.
A large chunk fell off when I rotated it.
There's quite a bit of it,as you can see. I think this is the issue

Can you confirm, 3rd and 6th connections, are those on the board (a total of 10, I counted), correct?
See photo called hp34c connector

https://imgur.com/gallery/chUj6
I put the big chip that fell off on the main circuit board so that you can see it.
I'm not very electronic savvy. I am a EE, but went into the software industry out of school
I need to see if we have a multimeter in the house.
Thanks for the help

[AndiGer]

Yes, right, the 10 connections on the board.

And as I can see: the inner strip is corroded. The one leading to the 3rd connection on the board. You can bridge it with an additional lead. Look where it is leading to and solder where you already have original solder joints. Soldering the lead at the battery side is not so simple because soldering to the battery contact will not connect very well, but is possible.

Look at this
http://keesvandersanden.nl/calculators/hp33c_inside.php

and this (last picture how Kees did it)
http://keesvandersanden.nl/calculators/h...pair_1.php

Andi
BTW: I am mathematician, have no deeper electronic knowledge

[dm123]

Hi Andi,

I knew before hand once I visually inspected the ribbon, with the info you gave that the anode was completely oxidized. The chunk that fell off completely severed the connection

I did find an old radio shack multitester, which itself had a corroded double AA. I cleaned it up, replaced the battery and calibrated the multitester and set it on lowest resistance (most sensitive)

Cathode and that middle node for charging the battery are strong to their respective connectors. The anode to 3rd is completely dead. I think with that chunk in place it was intermittent, hence the flickering display. I assume now, without testing it yet, there will be no display acrtivity, since the anode to connector 3 is severed. I think you can see it in that latest photo I posted. There is a lot of oxidation on that side of the strip.

It's a shame. The rest of the calculator is very clean. I saw all the LEDs lighting up. Is here anything that can be done at this point. .? I have not soldered in years, even if I could remove the old ribbon and replace it.

Update: after moving the ribbon around, the cathode is now unresponsive, due to cracking of the oxidation

Is the copper dangerous? I put gloves on for part of this, but touched some of it.....

[AndiGer]

Never thought about it is dangerous. As long as you don't eat it and wash your hands after working on it.
The broken cathode after moving the flex cable is often and the Achilles heel of the spice series. The flex will break at the border where the strips are coated.

I think you should find someone - a friend or neighbor maybe? - who can help you with the soldering. The calculator IMHO will work after this fix done.
As long as you can charge the battery outside the calculator as already mentioned no need to re-connect the river-left most connection - because there is no obvious place you can solder to without further disassembly. Otherwise you must remove the calculator's guts to remove the upper circuit board. Then you have the chance to clean the keyboard :-). Then be sure not to loose the 2 switch contacts.
Good luck

[dm123]

Thanks Andi

Yes the calculator will work once this is fixed. The connectivity to that first connector from the middle node is strong. I know I can't leave the ribbon in place after the change, too bad, because it would recharge the battery. I purchased the battery pack from that good seller on eBay. I do have a battery charger.but the batteries are banded together. What kind of charger would charge the banded battery pack?

[Geoff Quickfall]

Trace the circuit from the two battery contacts and the third charger contact point in the battery housing.

Personally I do not bother reconnecting the charge wire but you can. Here is a photo of the correct -ve and +ve solder points.

I cut the ribbon out of this 34C as it was cracked and corroded beyond saving. Combine this with the post I listed earlier in this thread:



Another view:



And look through the following post:

http://www.hpmuseum.org/forum/archive/in...-2111.html

Geoff

[dm123]

Hi Geoff, thanks. Will these batteries work in it once its reworked?

1.2 V 1.900 mAh. Eneloops rechargeable.

(I know never to plug in ac adapter with non-original or no batteries.)

I posted pics on the 25c thread.

http://www.hpmuseum.org/forum/thread-825...l#pid72492

[AndiGer]

Original batteries vs. today's batteries were a little bit shorter. If you choose today's batteries they will stress the battery terminal especially if you plan to take them out every time for recharging. Personally I think the terminals were designed to take the batteries out every other 5 years or so to replace them.
I bought some flathead rechargeable batteries about 49 mm long not connected by the permanent bridge but seperated. Connection on the opposite side of the terminals by a piece of a solder tab instead of aluminum foil.
Andi

[dm123]

Hi Andi would it be ok to split this new NiCd I just bought on eBay? The black part is soft foam and is stuck to the metal plate that joins the cathode ends of the pair. I can insert that and the metal plate into the 34c battery compartment. I will also be able to test and charge the batteries in my charger.