HHP-16K and 32K EPROM Emulators for HP-41 calculator series.

HHP-16K DIP switches

GRSLO CS-82ES Plus Scientific Calculator

And another Chinese calculator sharing the internal processor architecture with other Chinese brands.

All of them looks like the Casio models and even sports basically the same functions, although we can't say they are clones because the firmware and hardware is specific to these Chinese models.

They are able to work with 16-BCD digits internally, something not featured on the Casio models they try to look like.
The forensics test for this model result is: 8.999999998078897 exactly the same one as found on the Hoopson PS-12MS.

This brand name uses latin characters that are visually close to close the CASIO name: GRSLO

Specifications:
252 functions (Trig, Hyperbolic, Log/exp, power, Fraction, Sexagesimal, Base-n, 40 constants, Metric conversions, Simultaneous equations, Polynomials, Matrix, Complex, Coordinate conv,  Permutation/Combination, Standard Deviation and Regression. 
Equation solver
9 variable memories


Best served with Café da Ilha do Fogo:

Hoopson PS-12MS scientific calculator

This model can be found in some shops in Brazil.
I guess it is kind of rare, though.

A Chinese made machine distributed by "Mercoriental Importação e Exportação Ltda", copying the HP Voyager series style.

At first it looks like this model is cloning the Casio fx-82ms functions.
But the Mike Sebastian's Calculator Forensics test reveals a different beast inside.

This calculator seems to be able to work with 16 BCD digits internally, as the test result was: 8.999999998078897

A quick search in the Internet shows just a few machines with the same signature:

• Corner Office ATC-139
• Durabrand 828 (SC-1376)
• Fred Dual Power Scientific Calculator

Specifications:

• Two "AA" battery cells (3VDC)
• Two line display (text on top row, numeric on bottom)
• 10+2 digit numeric display
• 240 functions
• Made in China

Powering the calculator off will clear the display but the memory contents is preserved including the Ans register value.

Forensics test - extracting the remaining digits.

 
Dismantling the machine.
The back cover maintains the LCD display and the processor board in place.
Four small metal self taping screws need to be undone to remove it.
 

Mainboard PCB label: 82MS-9-2   13.06.14

After removing the back cover, the mainboard PCB and the LCD display are floating around.

Flexible flat cables interconnect the keyboard and display to the mainboard assembly.

The membrane keyboard is fixed using undone plastic rivets. Didn't try to dismantle it.

Reset key contacts on the left of the mainboard PCB assembly.

 Back side of the mainboard and LCD display. 

View from the unit top side.

Canon F-73P Scientific Statistical Calculator

This unit was made after May of 1984, according to the processor date code.

72 pages user manual, printed in Japan, 1983.

Handy little pocket calculator, CASIO style, with a useful set of features and a basic blind programming capability.

It has six operation modes: Decimal, Hexadecimal, Octal, 1-Var Stats, 2-var Stats, Program 1, Program 2.
Display mode supports Floating, Scientific and Engineering. Fix 0 to 7 digits.
One independent  memory register, six storage registers.
Programming:
45 program steps.
5 control instructions (Halt, Enter data, relative unconditional jump GoTo and two relative conditional jumps)

Calculator forensics test: 9.0000278593
Display mantissa digits: 10 digits
Internal mantissa digits: 11 digits

Getting the extra internal digit: (result - 9) * 1000000
 

Slim body with 70mm x 137mm x 8mm and just 75g weight.

Power supply: 3VDC 0.36mW (120µA nominal) from 2 x G13/LR44 1.5V battery cells.
Expected battery life: 4000 hours for G13 silver oxide, 1500 hours for LR44 alkaline.

Besides the hardware Power On/Off switch, this calculator features software Power Off and Power On functions along with inactivity Auto Power Off.

The hardware Power OFF switch wipes all the memory data.

However, the software OFF key will turn off the LCD display and put the processor in deep sleep mode while preserving all the memory contents. This is very well implemented in the Toshiba T6711 processor with less than 0.05µA of current consumption.

Current consumption measurements:
Power On idling: 30µA avg
Power On calculate 69!: 92µA avg
Power On running a looping program: 94µA avg
Soft Power Off: less than 0.05µA

Tear down.
Excellent quality stainless steel screws, hard to find these days on this kind of equipment.

Very well designed battery compartment.

The PCB is maintained in place by nine screws and eight lateral plastic latches.

To remove the PCB, it must be lifted from the lower keyboard side in first place, requiring gentle force on the plastic latches.
The LCD display is glued on the sides of the zebra strip connector and probably will come attached to the PCB. Cleaning the contacts is recommended to get a better LCD contrast.

The membrane keyboard is easily taken apart to be washed in warm water using dish washing detergent along with the plastic keys and case front panel and back cover.

LCD display, probably from EPSON.

SoC CMOS processor from Toshiba T6711 date code 4.E (1984, May).

HP-42S Scientific Calculator   current consumption

Some people complains about fast battery drain when using this calculator.
this should not happen, as the current consumption is very low under normal circumstances.
  
Assuming that the calculator passes the full self-tests, this suggests one of two possible causes:

1) - The battery batch you are using presents very high internal resistance due to a manufacturing defect or maybe they are out of date.
This results in a very fast voltage drop at the battery terminals especially under load (with the machine in power on state).

2) - Your calculator current consumption is way above the average.
This one is easy to spot as long as your multi-meter is able to measure current.

Here are the normal current consumption on a HP-42S, brand new, barely used:
(Test done using an external 4.5VDC power source. Any 4.5VDC 3R12battery will do,or else you may use 3 x 1.5VDC AA or AAA batteries in series installed in a battery holder)

Power off state: 9μA average (9 micro Ampere, to be clear)
Power On idle: 0.3mA average
Power On pressing keys: 2.5mA average

If you machine have much higher values, specially when in powered off state, then you need to check possible current drainage causes, starting from previous battery leakage (most common cause IMHO) to a bad bypass capacitor.

Casio fx-180Pa calculator easy fix for LCD display missing segments

It's a "Program FX" type calculator as Casio like to call it.

Typical education calculator supplied with an hard plastic protective case (not shown here).

Feature rich calculator for such a low cost machine.
It feels very light on the hand due to the reduction costs design choices.


This unit developed a fault in the LCD display, common on this type of calculators.
There were missing segments in some digits.
Although it was a easy fix. See below.

There is a reason for this back cover large recession.
To reduce production costs, this calculator uses the back cover as part of the keyboard assembly. Casio used this approach on other models too, like the ultra light and compact Casio fx-3900Pv model.

This is a unbelievable low current consumption design although being powered by a huge AA 1.5Volt battery cell.
Average power of just 0.00003 Watt translating to an avg current of 20µA.
The battery will last forever until eventually starts leaking and destroying the internal circuits.

The keyboard keys carbon contacts are installed at the back cover.

There is no conventional rigid PCB (print circuit board).
The keyboard matrix and SoC processor are deposited on a ultra thin plastic foil acting as a flex PCB that is fixed over the keyboard membrane by using melted plastic rivets.

There is no soldering at all. The battery bypass electrolytic capacitor leads are just melted to the plastic front cover, as well the battery terminals, and they connect to the main flex PCB by just the natural elastic pressure from the plastic foil with the help of the back cover.  

To fix the missing LCD segments, I used an very old trick that can work most of the times on this kind of LCD "flat cable" connections where the "wires" are just conductive paint deposited over a thin plastic foil.
Because the are no real wires and no conventional soldering involved, we can't use conventional tools and techniques to fix it.
However plain hot air can fix this kind of faults.
So I used a conventional air dryer over the flex PCB near near the LCD "flat cable" interconnection for a couple of minutes. Job done. I got a new high contrast LCD display.

SHARP EL-5120 Programmable Scientific Calculator

The SOLVER machine.

Compact, well built, direct algebraic logic calculator, with a handy uncommon 3 lines alphanumeric characters matrix display, from 1994.

Obviously the SOLVER capacity is the main feature of the model complemented by its programming ability. I didn't spend my time checking it in detail, but, here are some highlights taken from the manual:

Powered by a single CR-2025 battery cell.  3mW power consumption.
Contrast adjust by software.

Display: 14 characters and 2 exponents x 3 rows, 5x5 dot matrix.
Number of display digits: 10 mantissa + 2 exponent
Number of internal calculation digits: 12 mantissa

Variables:
27 named global variables (A,..,Z, θ) persistent between operation modes.
9 additional named local variables in each equation or program.
Last Answer memory.

Total user memory capacity: 1211 Byte. 
Memory manager shows free memory.
Memory is shared between Variables, Programs and Equations.
Each variable consumes 8Byte (where its name takes 1Byte).
Each new Program structure takes 32 Byte; each line takes 3Byte plus the number of characters (1Byte each) or commands (1Byte each).


Setup allows to chose Deg, Rad, Grad, Floating, Fixed, Scientific, Engineering, Fractions.
 

It has four Operation Modes:

• REAL - Using real numbers, perform standard operations, expression solver calculations, integration and statistical operations on one & two variable, factorials, combinations and permutations, as well as polar-rectangular;
• NBASE - Perform binary, octal, decimal and hexadecimal operations and conversions;
• SOLV - Calculate unknown variables using an equation;
• PROG - Create and use named programs in REAL or NBASE modes to automate simple or complex calculations. BASIC alike programming with input, print, end, labels, goto, gosub, if, logical conditions, wait, rem, statistical commands,

There are three ways to calculate an unknown variable concerning its SOLVER calculation methods:

• Expression solver - Uses substitution; 
• Integration - Uses Simpson rule;
• Solver functions - Uses Newton rule.