Finally acquired a Woodstock

[rprosperi]

(01-09-2018 03:14 AM)mfleming Wrote:  I struggled quite a bit to set up a Shapeways shop to make the design available for order (no markup) or download. Quite a pain! Try this link and PM me if there are problems. You'll like the case - no tape to hold the halves together.

https://www.shapeways.com/product/6NQAST...d=64514022

Mark,

I believe I somehow missed this case when you introduced it, and just saw this now. A 1-piece case is a very nice answer for this nagging problem.

Is this case designed for 'normal' cells with the button top on the positive end, or for 'flat top' cells like the originals that came with a Woodstock?

Also, do you have a recommended source for the required spring for the 'far' end of the holder? I've seen similar springs for '41 battery holders, but not sure if the case geometry is the same.

Nice!

[mfleming]

Hi Bob,

I'm using normal buttontop Eneloop cells and the replacement springs for the 41 battery case found on TAS. The battery holder snaps into the cavity with a nice fit and spring pressure keeps the batteries pressed tightly against the contacts inside. The holder requires a firm push downward to remove, so there's very little chance the holder will pop out of the calculator. The TAS springs use a thicker wire than the stock 41 springs and are almost fully compressed when the batteries are inserted.

The only change I made to the original design was to remove a couple of floating pieces. At the bottom of the case are two projections that slip into the well behind the two battery contacts and help hold the bottom of the case in place (excellent design!) It looked like the original designer wanted a hook to rise from the end of the two projections to provide further latching, but they were rejected during the design check. Not really needed in my opinion.

Having used an original battery holder and another two-piece Shapeways design, I can definitely recommend this one. It's a very clever piece of work by the original designer! Still haven't found time to match the original case color though

~Mark

[rprosperi]

(01-09-2018 03:48 PM)mfleming Wrote:  I'm using normal buttontop Eneloop cells and the replacement springs for the 41 battery case found on TAS. The battery holder snaps into the cavity with a nice fit and spring pressure keeps the batteries pressed tightly against the contacts inside. The holder requires a firm push downward to remove, so there's very little chance the holder will pop out of the calculator. The TAS springs use a thicker wire than the stock 41 springs and are almost fully compressed when the batteries are inserted.

Excellent, thanks for these details Mark. Gonna go get me one (well, 2).

Do you have a link or item # for the springs on TAS (or elsewhere)? I've done a few searches, and besides finding plenty of 41 battery cases (ranging up to $75+ !) I don't see a listing for just the springs. I'll search old posts as well; IIRC, Sylvain found some somewhere a couple years ago.

Update - Found it:

https://www.ebay.com/itm/6x-Copper-Spring-Coil-and-6x-Contact-For-Dual-18650-Lithium-Batteries/253193465702


Does this look like it will work (often the strand that connects across the bottom is diagonal, this one is straight)?

[Krauts In Space]

I fished my Woody in the bay right 10 minutes ago.
Googled for HP25, lead me to a fresh auction.
4 guys "just visiting", no bids (peeeeew!!!), buyed it, got it.
A fairly good HP25C with both manuals, charger (US, maybe UK, no European), pouch, box and 2 batt holders for 150 €/179 U$
Last auction ended with 161 €/192 U$ - without manuals and box.

[Dave Frederickson]

(01-09-2018 03:48 PM)mfleming Wrote:  Still haven't found time to match the original case color though

I was less than successful dying some 71B port covers dark brown. Do you have a recipe that works?

Also, if you like, I can add your battery holder to my Shapeways shop.

https://www.shapeways.com/shops/hpparts

Dave

[Krauts In Space]

(01-09-2018 05:17 PM)Dave Frederickson Wrote:  

(01-09-2018 03:48 PM)mfleming Wrote:  Still haven't found time to match the original case color though

I was less than successful dying some 71B port covers dark brown. Do you have a recipe that works?

Also, if you like, I can add your battery holder to my Shapeways shop.

https://www.shapeways.com/shops/hpparts

Dave

Give it a try with black tea, test it before to see if the color meets your mood

[Dave Frederickson]

(01-09-2018 05:34 PM)Krauts In Space Wrote:  

(01-09-2018 05:17 PM)Dave Frederickson Wrote:  I was less than successful dying some 71B port covers dark brown. Do you have a recipe that works?

Give it a try with black tea, test it before to see if the color meets your mood

That's a novel idea. I was using Rit dye, but if the color I'm going for is brown then that opens up other options. I wonder if coffee would work - maybe a dark roast like a Kona peaberry.

Dave

[larthurl]

(01-09-2018 03:14 AM)mfleming Wrote:  

(01-08-2018 10:06 PM)larthurl Wrote:  Hello Mark:

do you have a link to the shapeways version of the HP-25 battery holder you did?
I'd like to get one for my Dad's HP-25.

Thanks

.....Art

Hi Art,

I struggled quite a bit to set up a Shapeways shop to make the design available for order (no markup) or download. Quite a pain! Try this link and PM me if there are problems. You'll like the case - no tape to hold the halves together.

https://www.shapeways.com/product/6NQAST...d=64514022

~Mark

Thank you Mark. I just placed my order. Looking forward to seeing if new batteries will bring this heirloom to life.

btw, do you recommend AA alkaline or Enerloop AA rechargeables?

.....Art

[mfleming]

(01-09-2018 04:04 PM)rprosperi Wrote:  ...snip...
Update - Found it:

https://www.ebay.com/itm/6x-Copper-Spring-Coil-and-6x-Contact-For-Dual-18650-Lithium-Batteries/253193465702


Does this look like it will work (often the strand that connects across the bottom is diagonal, this one is straight)?

That's the one. I think you can order just the springs if you don't need the other parts. I'm thinking of shortening the spring a coil or two so it's not completely compressed. I'll post a picture so you can see what I mean.

(01-09-2018 05:17 PM)Dave Frederickson Wrote:  ...snip...

Also, if you like, I can add your battery holder to my Shapeways shop.

https://www.shapeways.com/shops/hpparts

Dave

That would be great (I've bought a few things from there!) I like the idea of HP parts in as few places as possible, and I'm unlikely to make any of my own. Just provide a reference to the original author, Chris Osborn (aka "FozzTexx") and the Creative Commons license (I'm going to add those details soon if I leave this up for a while).

(01-09-2018 05:34 PM)Krauts In Space Wrote:  

(01-09-2018 05:17 PM)Dave Frederickson Wrote:  I was less than successful dying some 71B port covers dark brown. Do you have a recipe that works?

Give it a try with black tea, test it before to see if the color meets your mood

Love it

(01-09-2018 07:36 PM)larthurl Wrote:  Thank you Mark. I just placed my order. Looking forward to seeing if new batteries will bring this heirloom to life.

btw, do you recommend AA alkaline or Enerloop AA rechargeables?

.....Art

Ka-ching! Now I can frame and display on the wall my first non-existent dollar bill from my first no-markup sale!

I'd go with the rechargeable batteries. Alkalines may last a little longer, but we're talking battery life of only a few hours. That'd get pretty expensive if you're buying a pair every day or two. A big plus with the Eneloop (or Amazon Basics-labeled version) is the low discharge characteristic. Holds a charge for many months without trickling away...

~Mark

[mfleming]

Here are a couple of pictures to illustrate the battery case with springs. The first has a 41 battery holder using the TAS springs to show them in a fully extended position. There are five coil loops for each. The battery case is flush with the back of the calculator, there are grips at the top to push the case down, and the gap at the bottom is the distance it must traverse for the top latch to come free.



This is the battery case removed and rotated 180 degrees. You can see how compressed the spring is above the battery button on the right. That I may clip a coil loop off and bend the tip inwards for contact with the battery.



Hope the pictures help!
~Mark

[rprosperi]

Thanks a lot Mark, all very helpful.

[Krauts In Space]

(01-09-2018 05:52 PM)Dave Frederickson Wrote:  

(01-09-2018 05:34 PM)Krauts In Space Wrote:  Give it a try with black tea, test it before to see if the color meets your mood

That's a novel idea. I was using Rit dye, but if the color I'm going for is brown then that opens up other options. I wonder if coffee would work - maybe a dark roast like a Kona peaberry.

Dave

I could imagine lots more "green" dyes, like: red wine, black coffee, black tea, red beets, brown balsamic vinegar, "molassed" (chewing) tobacco. Or try some sort of cola (Pepsi or Coke - it's your choice ). (Chewing) tobacco might work best, but ... the smell??? X)
Let's go scientific! Try any sort of dyeing liquid or stuff and see what comes out.
The color might be a specific combination of pastics with dyeing fluid.
Even pink could be possible B)

[larthurl]

[/quote]

Ka-ching! Now I can frame and display on the wall my first non-existent dollar bill from my first no-markup sale!

I'd go with the rechargeable batteries. Alkalines may last a little longer, but we're talking battery life of only a few hours. That'd get pretty expensive if you're buying a pair every day or two. A big plus with the Eneloop (or Amazon Basics-labeled version) is the low discharge characteristic. Holds a charge for many months without trickling away...

~Mark
[/quote]

Do you think any less leakage with Enerloops over traditional Alkaline?
It took me many years to learn my lessons on leaving batteries in electronic devices for long periods.

.....Art

[larthurl]

(01-09-2018 09:57 PM)mfleming Wrote:  Here are a couple of pictures to illustrate the battery case with springs. The first has a 41 battery holder using the TAS springs to show them in a fully extended position. There are five coil loops for each. The battery case is flush with the back of the calculator, there are grips at the top to push the case down, and the gap at the bottom is the distance it must traverse for the top latch to come free.



This is the battery case removed and rotated 180 degrees. You can see how compressed the spring is above the battery button on the right. That I may clip a coil loop off and bend the tip inwards for contact with the battery.



Hope the pictures help!
~Mark

Let us know how the clipping goes.
I ordered the springs too, and am curious what tool needed to cut the springs to size.

.....ARt

[mfleming]

(01-10-2018 06:30 PM)larthurl Wrote:  Do you think any less leakage with Enerloops over traditional Alkaline?
It took me many years to learn my lessons on leaving batteries in electronic devices for long periods.

.....Art

The HP25 Owners Manual states that a rechargable battery pack should last from 2 to 6 hours. I've experienced battery life at the low end of that range with Eneloop rechargables. Alkaline batteries wouldn't last mich longer.

I know what you mean about leaving batteries, even fairly new ones, in a lightly used electronic device. The only lesson I've able to discern after decades of experience is; The more expensive the device, the more likely a leak. Seriously. It's like they want to ruin your whole day.

If you've ordered springs and also bought the contacts, see if the contacts also work if bent properly. I suspect they might be a good alternative to the springs, but I don't have any to test that assumption. On my part, I'll let you know how trimming down the spring coils goes...

~Mark

[Dieter]

(01-11-2018 06:56 AM)mfleming Wrote:  The HP25 Owners Manual states that a rechargable battery pack should last from 2 to 6 hours. I've experienced battery life at the low end of that range with Eneloop rechargables.

The operating time in the manual refers to a capacity of 400...500 mAh as it was usual for NiCds in the Seventies. The Eneloops have 2000 mAh, i.e. at least 4x this capacity and thus 4x the expected operation time. So if you only get 3 hours from a correctly charged set of Eneloops something must have gone wrong.

(01-11-2018 06:56 AM)mfleming Wrote:  Alkaline batteries wouldn't last mich longer.

AA size Alkalines have a somewhat higher nominal capacity than NiMHs (2800 or 3000 mAh are typical values) but this does not always mean that the device can be powered 40 or 50% longer.

But again, if you say you can operate the calculator only 3 hours from a set of freshly and correctly charged AA Eneloops there definitely is something wrong. This would mean that the device constantly draws a current of 700 mA (!). How do you charge these batteries?

Dieter

[mfleming]

(01-11-2018 10:10 AM)Dieter Wrote:  ...snip...
But again, if you say you can operate the calculator only 3 hours from a set of freshly and correctly charged AA Eneloops there definitely is something wrong. This would mean that the device constantly draws a current of 700 mA (!). How do you charge these batteries?

Dieter

Well, the batteries were recharged but unused for several months which may have affected total capacity. Also, not exactly a stock HP25, as evidenced by the IR diode at upper right. I had the ACT replacement configured for full speed, internal ROM as I worked my way through all of the on-board Application Program examples, making occasional program listings. Not sure what the IR diode current draw is, but it has a decent print range.

The calculator went a little wonky just past the two hour usage clock mark, which I (perhaps hastily) interpreted as time for a recharge. I charge the batteries with an external Panasonic BQ-CC17 charger. If given a vintage wall charger, I'd heave it as hard as I can, as far away, as possible

~Mark
Edit: added charger model

[mfleming]

(01-10-2018 06:33 PM)larthurl Wrote:  Let us know how the clipping goes.
I ordered the springs too, and am curious what tool needed to cut the springs to size.

.....ARt

Here's the result of clipping two full turns from the spring, as shown in the left-hand side picture and the amount of spring compression with batteries installed on the right-hand side picture. The spring was cut with heavy duty wire cutters, and note how the end of the right-hand spring was bent inwards to make contact with the battery button.



I'll have to say this was a useful modification. The battery case is much easier to snap in and out, but the spring tension is still enough to maintain good physical and electrical contact between battery and spring. That likely puts less stress on the calculator battery contacts as well.

~Mark

[rprosperi]

(01-13-2018 12:20 AM)mfleming Wrote:  I'll have to say this was a useful modification. The battery case is much easier to snap in and out, but the spring tension is still enough to maintain good physical and electrical contact between battery and spring. That likely puts less stress on the calculator battery contacts as well.

Thanks for sharing your results Mark.

Did you cut both sides, or only the contact that touches the positive 'button' terminal. I presume both, but the photo could imply just one (or more likely was used to show the difference before/after trim)? Just wanted to make sure, as my parts are on their way.

[Bill Duncan]

Nostalgia time. Finally got my hp-29c going again after a few years. Fortunately I had taken the battery out, so the little leakage encountered didn't impact the machine.

What I finally ended up doing was cutting the crossbar out of the original battery. Spread the sides out a bit and pop the old cells out. Clean everything up a bit, pink eraser on the spring and the calculator contacts. Pop some new cells in. I had to shim out the ends a bit with some aluminum foil. Presto, the "Error" display. Back in business..