Casio fx-61F: Scientific Electric Formula 27

[jebem]

I am looking since long time after this little beauty from Casio, model fx-61F, the only brand that I'm aware of able to produce such a specific machine.

Even LeDuDu doesn't have it yet!

I was surprised to find out that a neighbor of mine, this old retired engineer, has got one in his possession. Unfortunately, he is not willing to part with it.

This is a 10 digits mantissa + 2 digits exponent algebraic calculator oriented for the electrical engineer.
Some features:
- programmable with 30 steps (one function/step) supporting basic tests and jump;
- 14 internal registers (from these, one user memory and 6 constant memories are non volatile);
- sporting dedicated keys for impedance, parallel, angle of deviation and angular frequency calculations;
- 27 built in electrical formulas;
- complex number basic arithmetic handling;
- statistical functions;
- dec/hex/bin/octal base conversions and arithmetic support;
- R<->P conversions;
- common scientific functions.

And because it is oriented for engineers, it allows you to select the engineering exponent by choosing the unit as symbols directly from the keyboard (from Pico to Mega only) which are translated to the correct exponent value in the display.

The cherry on top of this cake is the hybrid power supply based on solar power and a single 1.5 Volt GR-927 lithium battery cell.
You save power during daylight and can still work when in the shadow.


Image from a TAS seller repository:

[striegel]

Well, now you've done it. I didn't even know this existed before but now I have to find one.

Alan

[Hlib]

If I should have known better, never bought FX-3600PV in 1996 :-)

[jebem]

Well, I am pleased to inform that I got the machine!

I had to pay an extravagant amount of money to convince this "old dog" engineer (well, I'm getting there as well, 7 more working years and I will be retired if this Portuguese social welfare system doesn't fail on me before I do)

First the bad things:
- It looks cheap in your hands because it is very light, but then it is a small machine that should go nicely in your shirt pocket.
- It uses rubber keys that I dislike on CASIO machines, as they could do much better by using plastic keys as found on other CASIO models from the same era.

Now the good news:
- It works flawlessly.
- As usual on CASIO machines, the keys never fail to register, no matter how fast you type.
- To test the hybrid power supply on solar panel only, I removed the tiny small single battery cell (it brought a 1.5V AG7 alkaline inside). I can tell you this machine solar panel is super-sensitive, as it can wake up the calculator even in the dark shadow inside home. I never saw this performance before in any solar calculator.

More to come when I have the time to do the usual dismantling photo magazine.

[HP67]

I had a Casio solar scientific in this general style and I just can't find it. Every time I see a picture of a Casio in the similar style I wonder where it could be. It is not like me to lose something. And my apartment is not that big...

[Dave Britten]

(04-07-2016 10:49 AM)jebem Wrote:  First the bad things:
- It looks cheap in your hands because it is very light, but then it is a small machine that should go nicely in your shirt pocket.
- It uses rubber keys that I dislike on CASIO machines, as they could do much better by using plastic keys as found on other CASIO models from the same era.

Now the good news:
- It works flawlessly.
- As usual on CASIO machines, the keys never fail to register, no matter how fast you type.
- To test the hybrid power supply on solar panel only, I removed the tiny small single battery cell (it brought a 1.5V AG7 alkaline inside). I can tell you this machine solar panel is super-sensitive, as it can wake up the calculator even in the dark shadow inside home. I never saw this performance before in any solar calculator.

I rather like the rubber Casio keys, because they're so easy on the fingers, and, as you mentioned, they're so responsive. I've got a handful of Casios, and I don't think any of them have failing keys (electronically or physically - they definitely used good rubber). Still trying to track down an fx-6000g.

[Massimo Gnerucci]

(04-07-2016 12:24 PM)HP67 Wrote:  It is not like me to lose something. And my apartment is not that big...

Believe me, you don't need that much space to lose something...

I only recently found my misplaced PIL-box kit envelope (that I still have to assemble). And I knew it was in that room!

[jebem]

Here it goes the tear-down.

The LCD display is highly customized, with 3 main areas:
Annunciations, on the left a dot-matrix area to display alphanumeric symbols, and the central area the usual 7-segment numbers.

I just tried the Formula 1 (LC resonant frequency). Nicely done.




I measured the solar cells panel and it generates 3V under normal light conditions.
The hybrid power supply takes a 3V solar panel and a 1.5V battery backup, a couple of silicon diodes, two resistors and two capacitors.

Processor from Hitachi model HD62021A04.




It is not usual to see this LCD damage occurring on Casio displays, despite it is not visible when inside the case (well, not yet).
Some marks of humidity are visible on the PCB as well.

I think I am entitled to a refund...

[jebem]

(04-06-2016 01:05 PM)Hlib Wrote:  If I should have known better, never bought FX-3600PV in 1996 :-)

Yes, some of the Casio pocket models only allowed 'blind' programming, like this 61F, so we don't see what commands we inserted and there is no way to edit a program.
But these specific models didn't had real programmability in mind, as the machine was designed to natively offer most of the required features to most of the target users.

As I see it, these tiny small pocket machines were very popular among students and even professionals exactly due to is portability and great number of specialized features. We cold just put it in any pocket and we didn't notice it was there thanks to its small size and weight.

[jebem]

(04-07-2016 12:24 PM)HP67 Wrote:  I had a Casio solar scientific in this general style and I just can't find it. Every time I see a picture of a Casio in the similar style I wonder where it could be. It is not like me to lose something. And my apartment is not that big...

Hi, welcome back!

Exactly! So tiny and light they are that it an be anywhere.
Did you look between the pages of that FORTRAN advanced programming encyclopedia already?

[jebem]

(04-06-2016 02:06 AM)striegel Wrote:  Well, now you've done it. I didn't even know this existed before but now I have to find one.

Alan

If I see another one in my local flea market internet sites, I will let you know.
Good luck in your search, but the prospects are not good as the eBay only lists a couple of them sold in the last couple of years.

[jebem]

(04-07-2016 01:28 PM)Dave Britten Wrote:  I rather like the rubber Casio keys, because they're so easy on the fingers, and, as you mentioned, they're so responsive. I've got a handful of Casios, and I don't think any of them have failing keys (electronically or physically - they definitely used good rubber). Still trying to track down an fx-6000g.

Good point.
My only remark on rubber keys is that sometimes, despite being an odd situation, the key labels are weared down or even totally absent.
I rejected one fx-5000F because of his issue. The seller could not explain what hapenned, maybe a child used it as a toy scrapping it on the hard floor, who knows?

The 6000g and 6500g are on my search, fetch and get as well.
The 6300g is so much easier to find!

[Csaba Tizedes]

(04-07-2016 10:49 AM)jebem Wrote:  First the bad things:

Really bad thing about this calc is: no regression calculation, only one-var statistics
BTW my personal favourite CASIO is fx-50F. Far better than any other CASIOs (maybe the fx-4000P is slightly better but that is another category).

Csaba

[jebem]

The HD62021A04 SoC seems to be able to work at really low power supply voltages, most probably at around a minimum of 1 Volt.

Some more details on the hybrid power supply:

The two diodes allowing for solar panel/battery switching are marked on the PCB as MA700 and MA723 which should be schottky diodes. I measured them to check for Vf:
- The MA700 has a Vf=0.5V.
- The MA723 has a Vf=0.3V.
This later diode must have a lower forward drop voltage as it is in series with the 1.5V single battery cell. So for a fresh battery, the SoC will see around 1.2Volt when operating in very low ambient light conditions.

[jebem]

(04-10-2016 09:50 PM)Csaba Tizedes Wrote:  Really bad thing about this calc is: no regression calculation, only one-var statistics

Yap, we can't have all in one in such a small package, can we?

[HP67]

(04-09-2016 08:35 AM)jebem Wrote:  

(04-07-2016 12:24 PM)HP67 Wrote:  I had a Casio solar scientific in this general style and I just can't find it. Every time I see a picture of a Casio in the similar style I wonder where it could be. It is not like me to lose something. And my apartment is not that big...

Hi, welcome back!

Exactly! So tiny and light they are that it an be anywhere.
Did you look between the pages of that FORTRAN advanced programming encyclopedia already?

Hi Jose, thanks for the welcome meu amigo. We're still working things out. I need help with the math, I can figure the FORTRAN part out after that.

Enjoying your threads but going through a very busy period right now, only time to read a few thread and then have to get back to cleaning...ate logo!