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25c
04-27-2017, 03:52 AM (This post was last modified: 04-27-2017 04:06 AM by dm123.)
Post: #1
25c
I have a 25c with no battery pack or ac adapter. Does anyone know where I can find replacement batteries for this? I have AA rechargeable batteries, 1.2 v. Does it requires a battery pack or can it run from AAs. Thanks

Update I did find one here


http://www.ebay.com/itm/Rebuilt-Recharge...SwB-1Y58oX


Dm
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04-27-2017, 05:10 AM
Post: #2
RE: 25c
Try searching the HP museum website:

http://www.hpmuseum.org/cgi-sys/cgiwrap/...read=28349

http://www.hpmuseum.org/forum/thread-6840.html

http://www.hpmuseum.org/cgi-sys/cgiwrap/...i?read=335

Some non-museum sites:

http://www.keesvandersanden.nl/calculato...dstock.php

http://compgroups.net/comp.sys.hp48/re-b...ack/426650

http://slideplayer.com/slide/2379732/

Find a battery pack, cut the spine at each end, remove NiCd and replace with alkalines AA; or replace with NiMh AA but charge them with an after market charger. DO NOT USE THE WOODSTOCK WALL WART to charge the batteries while they reside in the calculator. DO NOT USE THE WOODSTOCK WALL WART without batteries in the calculator.

Geoff
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04-27-2017, 05:41 AM
Post: #3
RE: 25c
(04-27-2017 05:10 AM)Geoff Quickfall Wrote:  Find a battery pack, cut the spine at each end, remove NiCd and replace with alkalines AA; or replace with NiMh AA but charge them with an after market charger. DO NOT USE THE WOODSTOCK WALL WART to charge the batteries while they reside in the calculator. DO NOT USE THE WOODSTOCK WALL WART without batteries in the calculator.

I prefer to cut the spine only on one end (at the battery contacs), bend it outwards to remove and insert batteries. This will leave the battery pack more intact.

Bernhard

That's one small step for a man - one giant leap for mankind.
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04-27-2017, 08:46 AM
Post: #4
RE: 25c
That's true Bernhard, also leaves it looking more original.

Cheers,

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04-27-2017, 08:53 AM
Post: #5
RE: 25c
A photo of a battery pack with the spine removed allowing removal of the rechargeable NiMH to be removed f on the pack for external charging:

[Image: 1672A7AB-5C7F-4EAF-9D36-BDDDA1CCFD77_zpso4xcdoxb.jpg]
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04-27-2017, 11:09 AM
Post: #6
RE: 25c
You 're so barbaric Smile. My collectors heart is shocked.
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04-27-2017, 11:19 AM
Post: #7
RE: 25c
(04-27-2017 05:10 AM)Geoff Quickfall Wrote:  DO NOT USE THE WOODSTOCK WALL WART to charge the batteries while they reside in the calculator.

What is the reasoning behind this? So long as the calculator is off and the batteries are not overcharged, there shouldn't be a problem. Unless the batteries explode, what damage can result?

Pauli
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04-27-2017, 11:54 AM
Post: #8
RE: 25c
(04-27-2017 11:19 AM)Paul Dale Wrote:  What is the reasoning behind this?

To be able to charge newer NiMH batteries faster?
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04-27-2017, 12:02 PM
Post: #9
RE: 25c
(04-27-2017 11:19 AM)Paul Dale Wrote:  What is the reasoning behind this?

To avoid inadvertent handling errors like switching on.

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04-27-2017, 12:03 PM
Post: #10
RE: 25c
(04-27-2017 11:09 AM)HP-Collection Wrote:  You 're so barbaric Smile. My collectors heart is shocked.

Yes, I agree! Please cut only one side of the spine!

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04-27-2017, 01:16 PM
Post: #11
RE: 25c
Paul,

The ooooooooooooooooops factor! Turning on while plugged in to the wall but without a battery pack: ooooooooooooooooopops!
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04-27-2017, 06:44 PM (This post was last modified: 04-27-2017 07:44 PM by dm123.)
Post: #12
RE: 25c
Thanks all. I will find a holder somewhere and cut the spine at the ends
Are these batteries safe?. I don't want too much current frying out the calculator Sad
They are NiMh
Sorry so blurry. Had to reduce size to post. 1.2 V 1,900 mAh. Enteloops

Update: after reading through the links from Geoff, the battery specs look ok. Let me know if this is not the case. Thanks again
   

   
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04-27-2017, 07:57 PM
Post: #13
RE: 25c
(04-27-2017 06:44 PM)dm123 Wrote:  Thanks all. I will find a holder somewhere and cut the spine at the ends

http://www.hpmuseum.org/forum/thread-819...l#pid72007

Quote:Are these batteries safe?. I don't want too much current frying out the calculator Sad

Yes.
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04-27-2017, 09:25 PM
Post: #14
RE: 25c
Thanks dave
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04-28-2017, 01:13 AM
Post: #15
RE: 25c
Thanks dave
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04-28-2017, 07:39 PM
Post: #16
RE: 25c
(04-27-2017 07:57 PM)Dave Frederickson Wrote:  
(04-27-2017 06:44 PM)dm123 Wrote:  Thanks all. I will find a holder somewhere and cut the spine at the ends

http://www.hpmuseum.org/forum/thread-819...l#pid72007

Quote:Are these batteries safe?. I don't want too much current frying out the calculator Sad

Yes.

Hi Dave, does this look like the right one. Just want to be sure before ordering.

Woodstock bottom standard

I have an hp 25c
   
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04-28-2017, 08:39 PM
Post: #17
RE: 25c
That and the top.
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04-28-2017, 08:41 PM
Post: #18
RE: 25c
(04-28-2017 07:39 PM)dm123 Wrote:  Hi Dave, does this look like the right one. Just want to be sure before ordering.

Woodstock bottom standard

I have an hp 25c

Yes, this is the right one, you also need the Woodstock Top Std part.

Bernhard

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05-06-2017, 04:42 AM
Post: #19
RE: 25c
Hi all

I did get the battery pack from shapeways. The pack fits pretty good into the hp. The front top does not fit too well.

More importantly, i put it into the hp25c and I got nothing at all. I opened up the hp 25c and it looks clean as new.

I then tested the battery pack apparatus which has the coil springs from eBay in it mounted, and the multitester shows a nice 2.4 volts.

I am thinking, is it possible that the battery terminals are not making good contact with the terminals on the hp 25c?

Dm
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05-06-2017, 05:16 PM (This post was last modified: 05-06-2017 05:24 PM by Geoff Quickfall.)
Post: #20
RE: 25c
The two 'rivet tabs' take a lot of stress. I have found many continuity faults between the rivet contact and the PCA. I have found many attempted repairs with huge globs of solder.

Test:
- remove the battery pack.

- jump with wires directly to the rivet contact and try calc.

- no joy, remove the PCA from the shell.

- continuity test the rivet contact to a point further in the PCA.

- no continuity tester (ohm meter) then jump the power to a point just after the contact rivets on the PCA trace.

- typically the rivet contact is no longer contacting the PCA trace.

Repair:

- remove excess solder using flux to penetrate the rivet contact and trace interface.

- clean rivet contact with fine fibre brush or wire brush trying to avoid PCA trace.

- add flux and a small amount of solder to the PCA trace and rivet contact to establish new connection between them.

- confirm connection with continuity tester.

- reassemble and test.

- no joy and continuity between rivet contact and PCA is now good, then problem further up the PCA.

So a clean PCA usually means a bad rivet contact or a bad ACT. That, of course, after establishing no corrosion or oxidation damage. The rivet contacts may look good but under 40 years of battery changes and continuous flexing, they fail. The second failure other then a bad ACT is the board under the large resistor. This resistor warms up and cooks the PCA board to a nice well done toast look and may fail itself.

I have resurrected three non working 29c and a few 25s by correcting the contact rivet continuity.

Geoff

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