Poll: Should I bother with this HP 34C?

AndiGer · 04-28-2017, 03:32 AM

I think you can. But be sure you remember the polarity of the batteries.
An idea: Just release one side of the metal plate. This way a charger can hold both batteries anyway. So you know how to reinsert after charging.
Andi

pier4r · 04-28-2017, 09:38 AM

Had Adam success with his 34c?

dm123 · 05-12-2018, 10:13 PM

Hi all,

Sorry for reviving an old thread. I’m just getting to the bypass on my unit, a year later. Sad

Life’s interruptions.....

My question is to Geoff or anyone else who is familiar with the 34C spice power strip byass.

I practiced my soldering skills, and had a question before attempting the solder.

The -ve pin on the board is very small (pin 6). Is it ok to shove the stripped portion of the wire through the little hole to help position the wire prior to the solder?. Otherwise , I don’t know how to position the wire without a second person hold the wire for me. I can get a second person to help hold the wire.

Also, when soldering to the terminals, per Geoff’s photograph, should one shove the stripped portion of the wire through the hole and then solder, or try to solder directly onto the circular metal contact?

My last question is for tearing off the old cracked power strip. Can one just cut it close to the pcb board and leave the part on the pcb board intact. Same with the part that goes to the terminals, leave the overlay of the strip on the terminal board but trim it close to the board. I’d rather do less than more in trearing off the old power strip, if possible.

Thanks

brickviking · 05-13-2018, 01:37 AM

I was a bit ambivalent about voting on this, given I can see both sides of the equation. However, I voted "Yes".

So, first the list of pro's.

You'll have a classic LED calculator that was arguably the most powerful for its time aside from perhaps the HP-67.
It wasn't totally superseded by the 41C, though that overtook it for sheer features available even if the features weren't entirely duplicated.
You'll have a sense of achievement. Not many people these days have the patience to work through
repairing old calculators of that era and dealing with some of…the design issues of the era. Only you can
decide for yourself whether it's worth it to you.
Batteries last longer these days, but see cons.
The calculator's fast enough for the job. People might disagree with me, but let's face it, you're not likely
to be using it to solve for roots every time you pick up the calculator.
Almost all the functions of the calculator are exposed on the keypad. If you hunt hard enough, you'll
eventually find what you want to hit, even if it's h-PI h-x!.
Oh yes! They implemented the gamma function! How cool is that?
Plenty of useful exploration can still be done with this calculator. I had fun trying to model an inverse
to the Gamma function, only to find out decades later that such a function was undefined.

Now for my short list of cons:

It's an old LED-era calculator with the energy demands they had. Your batteries won't last anywhere
near as long as they would do in a LCD calculator. Thankfully, rechargeable batteries will last longer than
they used to merely by having far higher capacity.
Batteries might have to be "retro-fitted" or sourced with flat tops so they fit the battery holder.
Those batteries will probably have to be charged in an external charger, instead of relying on the slow
trickle-charge of the original power pack.
Apparently, the battery hatch and the framework nearby have a weakness in design. Other forum posts
have referred to this.
The LEDs aren't really very visible in bright lights. I struck this when I was using it in a supermarket on a regular basis.
It's definitely a far slower calculator with less memory capacity than later ones. That's only to be expected
for its age. You have to balance register requirements against lines of code.
It's keystroke-programmable. Looking at listings (basically column-row pairs plus bits) can do your head
in until you get used to the disconnect, especially if you're looking "through" indirect register references.

Conclusion: If I was going to have a Spice calculator, this would be it, though I'd go for one of the later
soldered models, not the earlier press-fit models.

(Post 218)

dm123 · (This post was last modified: 05-13-2018 05:23 AM by dm123.)

(05-13-2018 01:37 AM)brickviking Wrote: I was a bit ambivalent about voting on this, given I can see both sides of the equation. However, I voted "Yes".

So, first the list of pro's.

You'll have a classic LED calculator that was arguably the most powerful for its time aside from perhaps the HP-67.
It wasn't totally superseded by the 41C, though that overtook it for sheer features available even if the features weren't entirely duplicated.

You'll have a sense of achievement. Not many people these days have the patience to work through
repairing old calculators of that era and dealing with some of…the design issues of the era. Only you can
decide for yourself whether it's worth it to you.

Batteries last longer these days, but see cons.

The calculator's fast enough for the job. People might disagree with me, but let's face it, you're not likely
to be using it to solve for roots every time you pick up the calculator.

Almost all the functions of the calculator are exposed on the keypad. If you hunt hard enough, you'll
eventually find what you want to hit, even if it's h-PI h-x!.

Oh yes! They implemented the gamma function! How cool is that?

Plenty of useful exploration can still be done with this calculator. I had fun trying to model an inverse
to the Gamma function, only to find out decades later that such a function was undefined.

Now for my short list of cons:

It's an old LED-era calculator with the energy demands they had. Your batteries won't last anywhere
near as long as they would do in a LCD calculator. Thankfully, rechargeable batteries will last longer than
they used to merely by having far higher capacity.

Batteries might have to be "retro-fitted" or sourced with flat tops so they fit the battery holder.

Those batteries will probably have to be charged in an external charger, instead of relying on the slow
trickle-charge of the original power pack.

Apparently, the battery hatch and the framework nearby have a weakness in design. Other forum posts
have referred to this.

The LEDs aren't really very visible in bright lights. I struck this when I was using it in a supermarket on a regular basis.

It's definitely a far slower calculator with less memory capacity than later ones. That's only to be expected
for its age. You have to balance register requirements against lines of code.

It's keystroke-programmable. Looking at listings (basically column-row pairs plus bits) can do your head
in until you get used to the disconnect, especially if you're looking "through" indirect register references.

Conclusion: If I was going to have a Spice calculator, this would be it, though I'd go for one of the later
soldered models, not the earlier press-fit models.

(Post 218)

Thanks Viking.

Regarding the batteries, I know it’s not recommended, but I “flattened” some of my AA rechargeable with a towel over the battery and a hammer. I know it’s not advised, but it did work in flattening the batteries so that they fit in easily.

“Batteries might have to be "retro-fitted" or sourced with flat tops so they fit the battery holder.
Those batteries will probably have to be charged in an external charger, instead of relying on the slow
trickle-charge of the original power pack”

Is there a place that sells battery holders that bridge the one side of the pair, like the original holders did, and at the same time allow you to slide out the batteries so that they can be recharged. I’m trying to find out if there is an easy solution to this. I could not find any battery holders like this. This would be the bast solution

Also, another idea I had, is if one could stick a conducting plate on the nonterminal side of the battery compartment of the calculator so that the batteries could be imsertd right into the compartment directly.(with correct polarities ,right directions)

Negative Positive
Positive. Negative
I could not find any chargers that charge a bound battery pack as a pair, which is the third option,,given that the bound packs are available on eBay.

brickviking · 05-13-2018, 05:43 AM

(05-13-2018 05:19 AM)dm123 Wrote: Is there a place that sells battery holders that bridge the one side of the pair, like the original holders did, and at the same time allow you to slide out the batteries so that they can be recharged. I’m trying to find out if there is an easy solution to this. I could not find any battery holders like this. This would be the best solution.

I'd agree wholeheartedly with this, given that modern methods now allow for perhaps 3d-printing them up.

(05-13-2018 05:19 AM)dm123 Wrote: Also, another idea I had, is if one could stick a conducting plate on the nonterminal side of the battery compartment of the calculator so that the batteries could be imserted right into the compartment directly.(with correct polarities, right directions)
|+ ===== -
|- ===== +

I could not find any chargers that charge a bound battery pack as a pair, which is the third option,,given that the bound packs are available on eBay.

I actually found I could unbond the two batteries for charging, though I suspect it's not easy. I don't remember exactly how it was done, given that it was 1994. From what I remember, it's a metal framework around a plastic centre, with two slots for the batteries and one end free, exposing the two relevant ends. Obviously plugging the batteries back into the cradle the right way around is essential. If you can find the solution you mentioned above, that would be the best way around, but you'll still need a metal plate bridging one end.

(Post 219)

Zaphod · (This post was last modified: 05-13-2018 06:28 AM by Zaphod.)

(05-13-2018 05:19 AM)dm123 Wrote: Is there a place that sells battery holders that bridge the one side of the pair, like the original holders did, and at the same time allow you to slide out the batteries so that they can be recharged. I’m trying to find out if there is an easy solution to this. I could not find any battery holders like this. This would be the bast solution

Also, another idea I had, is if one could stick a conducting plate on the nonterminal side of the battery compartment of the calculator so that the batteries could be imsertd right into the compartment directly.(with correct polarities ,right directions)

This manufacturer I found does a plethora of battery terminals and plates (they also do cell holders too)

http://www.keyelco.com/category.cfm/Batt...404/id/410

They are stocked by most of the big distributors (Mouser, Digi , RS and Farnell etc).

Dieter · (This post was last modified: 05-13-2018 08:32 AM by Dieter.)

(05-13-2018 05:19 AM)dm123 Wrote: Regarding the batteries, I know it’s not recommended, but I “flattened” some of my AA rechargeable with a towel over the battery and a hammer.

"Not recommended" is not quite the correct term here... #-\

(05-13-2018 05:19 AM)dm123 Wrote: Is there a place that sells battery holders that bridge the one side of the pair, like the original holders did, and at the same time allow you to slide out the batteries so that they can be recharged. I’m trying to find out if there is an easy solution to this. I could not find any battery holders like this. This would be the bast solution

FWIW, here is my "best solution" for the 34C: Take a lok in the battery compartment. On the left you'll find the two contacts for + and – while on the right hand side there is a small metal plate – if I remember correctly, I may be wrong here. I removed this plate (if there was one ;-)) and replaced it with a piece of aluminum foil, folded several times. This way two standard Sanyo/Panasonic Eneloop AA cells (with standard button top) fit nicely into the compartment. You can do even better if you replace the aluminum foil with something more suitable.

(05-13-2018 05:19 AM)dm123 Wrote: Also, another idea I had, is if one could stick a conducting plate on the nonterminal side of the battery compartment of the calculator so that the batteries could be imsertd right into the compartment directly.(with correct polarities ,right directions)

Exactly – I see you got the idea. ;-)

(05-13-2018 05:19 AM)dm123 Wrote: I could not find any chargers that charge a bound battery pack as a pair, which is the third option,,given that the bound packs are available on eBay.

A battery pack with 2xAA is a standard item that can be found in any decent eletronics store. There are also battery specialists that will build any pack you like from any cells you want. You'll also find smart chargers that are suitable for packs from, say, 1 to 6 cells. These are common items in the RC model world (cars, airplanes etc.), but the most chargers may be overkill for your application.

The solution with two standard AAs and a thin metal connection works fine for me.

Dieter

AndiGer · 05-13-2018, 11:39 AM

For charging a connected pair of flattops I simply modified a broken hair cutting machine that contained 2 AA cells.
Just use the charger and broke away some plastic parts of the "battery case".

dm123 · 05-13-2018, 06:50 PM

(05-13-2018 08:31 AM)Dieter Wrote:
(05-13-2018 05:19 AM)dm123 Wrote: Regarding the batteries, I know it’s not recommended, but I “flattened” some of my AA rechargeable with a towel over the battery and a hammer.

"Not recommended" is not quite the correct term here... #-\

(05-13-2018 05:19 AM)dm123 Wrote: Is there a place that sells battery holders that bridge the one side of the pair, like the original holders did, and at the same time allow you to slide out the batteries so that they can be recharged. I’m trying to find out if there is an easy solution to this. I could not find any battery holders like this. This would be the bast solution

FWIW, here is my "best solution" for the 34C: Take a lok in the battery compartment. On the left you'll find the two contacts for + and – while on the right hand side there is a small metal plate – if I remember correctly, I may be wrong here. I removed this plate (if there was one ;-)) and replaced it with a piece of aluminum foil, folded several times. This way two standard Sanyo/Panasonic Eneloop AA cells (with standard button top) fit nicely into the compartment. You can do even better if you replace the aluminum foil with something more suitable.

(05-13-2018 05:19 AM)dm123 Wrote: Also, another idea I had, is if one could stick a conducting plate on the nonterminal side of the battery compartment of the calculator so that the batteries could be imsertd right into the compartment directly.(with correct polarities ,right directions)

Exactly – I see you got the idea. ;-)

(05-13-2018 05:19 AM)dm123 Wrote: I could not find any chargers that charge a bound battery pack as a pair, which is the third option,,given that the bound packs are available on eBay.

A battery pack with 2xAA is a standard item that can be found in any decent eletronics store. There are also battery specialists that will build any pack you like from any cells you want. You'll also find smart chargers that are suitable for packs from, say, 1 to 6 cells. These are common items in the RC model world (cars, airplanes etc.), but the most chargers may be overkill for your application.

The solution with two standard AAs and a thin metal connection works fine for me.

Dieter

Hi Dieter, thanks for your suggestions. Unfortunately there is no metal plate on the 34c, as the original hp battery pack was what bridged the two nonterminal sides of the battery. They sell these packs on eBay, and Andy has a recharger that works with the bound batteries. My recharger has a very thick separator between battery insertions and won’t work unless I break the batteries apart.

I do have aluminum foil tape and used that on the nonterminal side of the 34c battery compartment, but it tears easily when taking out and inserting the batteries.

I’m looking at the other link just sent out at this battery supply place and looking for a thin plate option, to be glued (? Not sure if this is safe due to heat) to the nonterminal side .

http://www.keyelco.com/category.cfm/Term...1/c_id/771

Zaphod · 05-13-2018, 07:04 PM

What about:
http://www.keyelco.com/category.cfm/Slid...39/id/1218

dm123 · 05-13-2018, 08:03 PM

(05-13-2018 07:04 PM)Zaphod Wrote: What about:
http://www.keyelco.com/category.cfm/Slid...39/id/1218

Thanks. I think I found a good option.

https://www.amazon.com/Tenergy-2000mAh-R...AYDV5&th=1

These are flat heads. Both batteries come with the metal tab already soldered to negative. I would bend the tab out on one (they have a picture of the folded metal tab in the 5th photo). I could leave it bent out and it would still insert into the charger. So would not have to keep bending it back and forth.

Inserting it into the 34c would work fine as the tight fit would cause the other battery to contact.

So insertion would be

Top battery. Negative (leave tab bent in or remove) ———-positive
Bottom battery. Positive——————————————————negative (bend tab out)

https://www.amazon.com/Tenergy-2000mAh-R...AYDV5&th=1

Dieter · 05-13-2018, 08:06 PM

(05-13-2018 06:50 PM)dm123 Wrote: Hi Dieter, thanks for your suggestions. Unfortunately there is no metal plate on the 34c, as the original hp battery pack was what bridged the two nonterminal sides of the battery.

Yes, I remember.

(05-13-2018 06:50 PM)dm123 Wrote: They sell these packs on eBay, and Andy has a recharger that works with the bound batteries. My recharger has a very thick separator between battery insertions and won’t work unless I break the batteries apart.

What kind of charger is this? And how does it charge the batteries, i.e. what kind of charge control is used?

(05-13-2018 06:50 PM)dm123 Wrote: I do have aluminum foil tape and used that on the nonterminal side of the 34c battery compartment, but it tears easily when taking out and inserting the batteries.

You have to fold it a few times so that you get, say, a four layer insert. ;-)
I have had no problems with inserting and removing the batteries. At least not in the last ten years.

(05-13-2018 06:50 PM)dm123 Wrote: I’m looking at the other link just sent out at this battery supply place and looking for a thin plate option, to be glued (? Not sure if this is safe due to heat) to the nonterminal side.

That's another option – something like "aluminum foil deluxe". ;-) Maybe you don't even have to permanently attach it to the case at all.

(05-13-2018 06:50 PM)dm123 Wrote: http://www.keyelco.com/category.cfm/Term...1/c_id/771

I can't see how one of these parts may be of any use for this application. The link Zaphod posted looks more promising: take a look at part #5227. There also is a datasheet with the exact dimensions, e.g. the thickness (1,2 mm). But I doubt they will sell you a single piece of this. Maybe you can build something similar yourself.

Dieter

Zaphod · (This post was last modified: 05-13-2018 09:03 PM by Zaphod.)

(05-13-2018 08:06 PM)Dieter Wrote: I can't see how one of these parts may be of any use for this application. The link Zaphod posted looks more promising: take a look at part #5227. There also is a datasheet with the exact dimensions, e.g. the thickness (1,2 mm). But I doubt they will sell you a single piece of this. Maybe you can build something similar yourself.

Dieter

Digikey will sell you just one (with a handling charge of course) https://www.digikey.co.uk/product-detail...ND/2342488

Mouser too:
https://www.mouser.co.uk/ProductDetail/K...qonEdMH0JQ==

Of course if you're ordering along with other stuff and get it over their threshold you'll pay no handling charge.... (maybe get someone who uses them a lot to order one for you )

I'm waiting myself to build an order up past £33 so I can add some part 181 AAA spring terminals for that Sharp pocket computer I received with corroded terminals

dm123 · 05-15-2018, 01:18 AM

Hi all,,
I did the soldering and wiring, but how can one get the bottom cover back on? The wires get in the way of the top ( terminal board) sliding into the bottom housing.

Thanks