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Victor 18-1441 Desktop Calculator

Updated 8/16/2022

This Victor 18-1441 is one of a number of of different calculators in the of 1800-Series introduced by Victor Comptometer Corporation in 1971. A number of different calculators were made in the series, with varying model numbers and capabilities. The 18 in the model number signifies the 1800 series, with the first two digits (14) of the model number defining the number of digits of capacity of the machine, and the last digit signifying that the machine has one memory register. Apparently three different models of the 18-144x calculators were made, the 1440, with no memory functionality, the 1441 exhibited here with a single memory register, and the 1442, with an additional memory register. It is suspected that all three of these machines are identical inside, with the only difference between them being the inclusion of the necessary memory function keys on the keyboard. Other 1800-series machines also were made, including two 18-154x series machines, the 18-344x printing calculators, and the 18-1721 Scientific display-only calculator.

Inside of the Victor 18-1441

This calculator dates from the late 1971 time frame based on date codes on parts in the machine. It uses a 6 chip Large Scale Integration (LSI) chip set made by Rockwell for its the calculating logic. All of the LSI's are dated in the October 1971 time frame, and other components in the machine share similar dating. This makes the Victor 1800 a fairly early all-LSI machine.

Closer View of Rockwell LSI's

The Rockwell-fabricated chips are numbered 10177, 10178, 10179, 10180, 10182, and 15000, and are packaged in 42-pin ceramic packages. The curator does not know if there ever was a 10181 chip, but it is clearly not in the sequence of part numbers. Perhaps the original 10181 chip had problems, and was superseded by the 10182, but that is only supposition. The chips are packaged in what can be best described as "zig-zag" packages, which are technically known as QIP (pronounced like quip) packaging, which stands for Quad In-Line Package. On a QIP-packaged IC, the pins coming out the side of the package are arranged in two alternating lengths so that the pad pattern on the circuit board that the pins connect to form a zig-zag pattern, with two rows of pins of each length. This arrangement allows for tighter spacing between the pins of the IC than other pin out methods, saving space on the circuit board.

The 10177 through 10180 and 10182 chips are common to all of the 1800-series display-type calculators. These five chips combine to form the a micro programmable calculator-specific "CPU" (Central Processing Unit) that is programmed to carry out the function of the calculator. The sixth chip, the 15xxx (in the exhibited calculator, part number 15000) device is a custom, mask-programmed read-only memory (ROM) that contains the microcode that gives the calculator its functionality.

The top-of-the-line Victor 18-1721 scientific calculator shares an identical main logic board with the 10177, 10178, 10179, 10180 and 10182 chips, but taking the place of the 15000 chip in the exhibited (18-1441) calculator, is a chip numbered 15320. This chip contains the specific microcode for operating the much more advanced 18-1721 calculator. The microcode for the 18-1721 contains the additional code to perform the complex scientific functions that the calculator provides. It appears that the three digits after the '15' in the microcode ROM part number identifes which microcode and revision is programmed into the read-only memory at the factory.

It is possible that there are different versions of the microcode ROM for a given model of calculator depending on when the calculator was produced. For example, there may be a different chip replacing the 15000 chip in a later version of the 18-1441 calculator that has a different part number and contains updated microcode. Different versions of the microcode for a given 1800-series calculator could indicate that a bug was found and new microcode issued at some point in the production of the calculator to fix the bug, or perhaps there were efficiency improvements to the code that provided faster operation for the math functions of the machine, with the more efficient microcode included at some point in production during the calculator's production lifetime. There is no way to know if there were different version of the firmware ROM for the same model of calculator other than to survey the remaining 1800-series calculators that still exist to identify the 15xxx part number.

Unfortunately, it appears that the 15xxx-parts in the Victor 1800-series calculators suffer from a common malady whereby the parts fail over time. Since these calculators are around a half-century old, it is not terribly surprising that parts would fail, but it only seems like the 15xxx ROM parts tend to fail. The other chips that make up the microcoded engine that run the calculators seem to fare much better. It was clearly never expected that these calculators would be operating 50+ years after they were manufactured, so the fact that some components suffer an age-related failure is not really a big deal, because at the time these calculators were manufactured, the general life-expectancy of a desk calculator was typically somewhere in the range of five to seven years, with the calcualtor being replaced by vastly superior technology after a few years of use, even if the machine still worked.

It is believed that the 15xxx ROM chip is the most complex chip of all of the chips in these calculators, and because it was a stretch of the state-of-the-art of Rockwell's MOS LSI manufacturing processes, there could be age-related defects that develop over time, most specifically the condition known as metallization creep, that renders the chips no longer functional. Even a single bit in the ROM that goes bad could result in a non-functional calculator. It seems that a great many of the Victor 1800-series calculators, at least the display-type models, tend to suffer from malfunctions ranging from no sign of life at all, to no response to the keyboard with random patterns in the display. It is a relative rarity to find one of these calculators that is operational today. In cases where an 1800-series calculator exhibits a malfunction, it is highly likely that the ROM chip is at fault, and unfortunately, replacements for these chips haven't been manufactured for well over 35 years. The chips contained proprietary microcode, and were custom programmed by Rockwell per Victor's specificaftions, and as such were not documented in terms of their functionality or microcode content in any publicly-accessible way, and any such documentation that may have existed at Victor Comptometer or Rockwell is long since discarded.

If you own a Victor 1800-series display-only calculator, the Old Calculator Museum would be greatly appreciative if you would be willing to carefully open up the calculator and note the part number of the chip that begins with "15", and has five digits in the part number, e.g., 15320. All of the other chips should have chip part number that begin with 101, and have two more digits, so it is quite easy to pick out the ROM chip with the 15 at the beginning of its part number. If you could then note the model number of the calcualtor, (e.g., 18-1441) from its model/serial number tag, and send an E-Mail to the museum providing this information, it would be most helpful in compiling a list of the ROM part numbers for the various versions of Victor 1800-series display-only calculators.

The chips are mounted on a nice quality fiberglass double- sided circuit board, with plaated-through feed-through holes providing connections between the two sides of the circuit boards. Along with the LSI integrated circuits there are a few basic discrete support components such as diodes, resistors and capacitors. The main logic board connects to other sections of the calculator via flexible ribbon cables. Even the power supply connects to the main board through a flexible cable. The power supply and main board are mounted to the base of the case, with the keyboard, display, and display driver circuits mounted to the top part of the case.

The Gas-Discharge display panel of the Victor 18-1441

Hybrid Display Driver Modules

The 1800 uses a gas-discharge display panel similar to a Burroughs Panaplex, however, it appears to have been manufactured before Burroughs introduced the planar Panaplex display. In the exhibited calculator, there is no indication of the manufacturer of the display can be found. The display is of a somewhat different design than Panaplex panels. Burroughs Panaplex panels use a clear metallized electrode electro-deposited on glass in front of the segments, whereas the panel used in the exhibited calculator has a wire grid (similar to that of a Nixie tube) in front of the segments. It is possible that this display is an example of an earlier panel-type display invented by Burroughs that was marketed as the Segmatron display. The Segmatron display was developed prior to the Panaplex display technology as a way to put multiple segmented digits (up to sixteen digits) and decimal points inside a single display panel, providing common connections to each of the segments and decimal points inside the panel, as well as connections to a special grid positioned in front of each digit position on the panel. This arrangement required far fewer connections to the panel due to the panel being designed to utilize multiplexing rather than driving each digit individually. This display panel, with sixteen digit positions, would require sixteen connections for the digit grids, and nine connections for each of the the nine segments used in rendition of the digits, one connection for the common decimal points, as well as another connection for a larger common grid across all of the digits that carries a high voltage (+180 Volts) that provides just below the potential required to light up a digit segment, but is enough that once an individual digit grid is electrified with around 40 Volts, and with a small voltage on segments desired to be lit up, the combined voltages trigger the segment(s) to light up and stay lit even if the digit grid returns to 0 Volts. This makes a total of 27 pins versus 177 pins if each of the segments and decimal points had to be brought out of the panel on separate pins.

The panel has 16 positions, with the right-most digit position used for indicating sign (-), and the far left position serving as an indicator for overflow conditions (F), leaving fourteen positions available for numeric display. The display panel has a fairly large circuit board crammed with custom hybrid devices that serve as the display drivers. The hybrid modules contain a ceramic substrate upon which passive components, along with discrete high-voltage transistor chips that provide the high-voltage switching to drive the gas-discharge display. Display digits are formed from nine segments. The standard seven-segment arrangement is modified to add two vertical segments wired together that allow the '1' to be displayed centered within the digit. Each digit position also contains a right-hand decimal point. The display logic inside the LSI chipset perform both leading and trailing zero suppression.

Victor 18-1441 Keyboard Layout

The Victor 18-1441 is a four-function calculator with one memory register. The calculator operates pretty much as expected for a machine of this vintage, with the [+] and [-] keys operating adding-machine style. For example, to perform 10 - 8, one does 10 [+] 8 [-] and the answer of 2 appears in he display. Multiplication and division use the [=] key to generate the result. The machine has a full-time constant, which operates in all four functions. This can be demonstrated by pressing "[1] [+]", followed by repeated presses of the [+] key, which results in the display incrementing by one for each press of the [+] key. A constant in all four functions is a useful ability that is not shared by many calculators from this era. The memory functionality of the machine is fully featured, with [M+] and [M-] keys adding/subtracting the content of the display to/from the memory register without affecting the display. The [=+] and [=-] keys serve to terminate a multiply or divide operation (like the [=] key), but also adds/subtracts the resulting answer to/from the memory register, leaving the result of the multiply/divide operation on the display. This is very useful for sum-of-products types of operations. When the memory register is non-zero, a small round indicator on the right side of the display panel (labeled "M1") lights. Rounding out the memory functions, the [MR] key recalls the content of the memory register to the display, and the [MRC] key recalls, then clears, the memory register. The [EX] key exchanges the operands of math functions, IE: [4] [÷] [8] [EX] [=] will result in 2 (having performed 8/4 rather than 4/8). The [C ALL] key clears everything except the round-off setting, including the memory register. The [C] key clears overflow indications, as well as clearing the display to allow entry errors to be corrected.

The Unusual "Round" Function Setting (showing the machine is set to round to 9 digits behind the decimal)

The Victor 1800-series display-only calculator are full-floating decimal point machines, meaning that the decimal point is automatically placed to provide maximum precision of results. However, the 1800-series calculators add an unusual twist icture by providing a special round-off function. Two keys on the keyboard with ∩ symbols on them; one [∩ SET], and the other [∩]. These keys are used to set the position of, and perform, a round off function. The [∩ SET] key, when pressed (see image above), switches the display to show a single digit from zero through nine, indicating the current number of digits behind the decimal point that the machine will round off to when the [∩] key is pressed. Pressing any digit from zero through nine while holding down the [∩ SET] key will set a new rounding position for the machine. Releasing the [∩ SET] key restores the display to its original content. Once a rounding setting has been established (the calculator by default powers up with a sensible rounding setting at 2 digits behind the decimal point), any time that the operator wishes the number on the display to be rounded-off to the desired setting, the [∩] key is pressed, and the number on the display is immediately rounded to the selected number of digits.

Overflow Indication (F)

The 18-1441 is quite a fast machine, with virtually instantaneous results, even on the "all-nines divided by one" benchmark. A guess would be that the all nines division takes perhaps 60 to 80 milliseconds...fast enough that the result seems virtually instant to a human operator. During calculation, the display is quiet, with no spinning of the digits or other indication that the calculator is busy. The machine is good about detecting overflow conditions, by displaying an "F" in the left-most position of the display, and logically locking the keyboard. Overflow detection is also activated when division by zero is attempted. Pressing the [C] key when overflow lockout exists clears the display and the overflow condition, resetting the machine for continued use.

This great old calculator was found at a flea market by my aunt, who was always on the lookout for interesting old calculators for me when she was out treasure-hunting. The machine is in like-new condition -- whomever owned it took very good care of it. Total price paid: $0.10. Thank you, Auntie Dyann.

Text and images Copyright ©1997-2023, Rick Bensene.

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