Vintage Calculators

An interesting vintage calculator, based off of the Sharp EL series which were a Japernise import were rebranded by Dixens when they use to exist. It is a basic 4 function unit, uses LSI as the logic is divided between two chips. The display is a rather nice 8 digit separate VFD tubes with interestingly styled digits.

Rather lovely VFD tubes. Not to common on hand heal calculators.

One of the processor chips. This chip set uses 2 chips.

Diodes & resistors.

Display driver chips.

I use to use this as my carry to work calculator, when I use to work in London. It often lived on the desk in the office & only came home on occasion, usually to charge the battery.

Now I perpetually work from home it lives in my calculator display cabinet.

But the nice thing about this image is you can see the funky style of the digits in the VFD tubes. I like the way they are rounded & also how zero is displayed with only half the segments in a VFD tube. This was common in Japernise calculators of the era, even some normal styled 7-segment displays would show zero is half a digit in the display.

The construction is once again, built to last, hence even 50 odd years later this calculator still functions, only using a 2 cell LiPo battery for power instead of the nasty Ni-Cad's it originally used. Which of course had leaked, but was luckily contained in the pack casing.

CASIO FX-730P

This is a rather nice programmable calculator, it uses the BASIC programming language which was popular on home computers of the 80s. It only has a signal line LCD display but, does have status segments on the display that tell you the mode. It is a scientific calculator although the functions are a little tricky to use, just like accessing the programming mode is a little tricky, but makes sense once to lean it.

Another 4 function calculator from 1973. It is a signal chip calculator so it is pretty much large pocket sized. As it has a VFD, there is a HV buck driver to up the voltage to about 30V, been a while since I last measure the output voltage. The chip in these calculators is a beautiful white ceramic. It does have a constant mode, quite common even in the oldest calculators.
Restoration video here: ROYAL Digital 5-T Restoration

The C-570 chip set was used in a few low cost calculators, it will actuality try & calculate a divide by zero sum, the display will go glitch & perpetually count.

9 digit VFD, meant to be 8 digit, but I had to replace the original as it got broken. The style of the VFD is the same as the original though.

The Sinclair Cambridge was released shortly after the Sinclair Executive. Once again uses a singal chip to do the calculation logic, it does have a display driver chip. Interestingly the C550 is similar to the Royal Digital 5-T chip set as it will behave the same way when you try to divide by zero. It is very cheaply built, like to mike tray plastic levels & also came as a built it your self kit. Mine required some fixing of a mistake that was probably made in the 70s. The kits will often got for more money than fully built calculators which is a shame.

C550 chip set is a lovely white ceramic with gold plating, it is similar to the C-570, probably part of the same range.

Lovely shot of the bubble LED display. Sadly digital cameras just can't catch the true pure RED these 70s LED produce. Will need to do a film shot at some point.

A zoomed in macro shot of the bubble LED's. Interestingly one segment is made up of 4-5 individual microscopic LED's. In the 70s it was not possible to manufacture large LED chips, that tech started to become available in the late 70s to early 80s.

This is my main desk calculator. Another 70s beast. This one runs on an Hitachi chip set so is from the era where the Japernise took over the calculator market. Once again a standard 4 function with constant function. The other chips seem to handle multiplexing of the display & keypad, quite common in calculators of this era. Has a nice 8 digit VFD comprising of 8 individual tubes.

The individual VFD's & a close up. Each tube only has one filament, but does have a control grid, handy as they are multiplexed.

The main calculator IC. Performs as you would expect a 4 function calculator chip to perform. The display register is filled with garbage when first turned on. That is the only quirk.

More support chips with some ceramic capacitors. Hate the cap codes used on these.

One of the support chips by another Japernise manufacture, Toshiba. Back when they made good stuff.

This is my only Nixie tube calculator, I waited years to get hold of one of these, talking almost 20 years. This now takes pride of place as my workbench calculator. The chip set in this bad boy are still LSI, but is a 6 chip array of lovely white ceramic gold plated pin chips. Real built to last construction that you just don't see today. Everything is socketed & the keyboard is a thing of pure beauty. The six chips are divided into 2 groups, A & non-A, not sure why at the moment. Will investigate when I next need to take it apart for repair. The six chips in the chip set are:

The left three of the chip set. Divided into the A group of chips.

The right three of the chip set. Divided into the non-A group of chips.

The keys use reed switches actuated by magnets, so theoretically should not ware out. Beautiful construction, built to last.

This lovely beast was my main calculator I used on my desk for quite few years, until I moved into my own house. Even then it was still on my computer desk. It only really got moved to the cabinet when got the Nixie calculator. It did get moved to be the main workbench calculator when I moved the current desk calculator into its present location.

This calculator uses a 9 digit aka 9 tube gas plasma display, or as I call them 7-seg Nixies. This is quite rear for a gas plasma display for two reasons. one each display is its own tube & two, the calculator runs on battery's, there is not even an option for mains power which is unusual for a calculator of the 70s as battery's were more expensive back then. Of the 9 digits, 8 are used for the numbers & the 9th is used as the overflow indicator or negative indicator.

I still need to print a battery cover for this calculator. I call it Kovac The Killer Calculator as Kovac sounds a little Soviet to my aspie brain. I also had replace the HV regulator diode in it as the old 70s one kicked the bucket.

HP 12C

This is probably my most modern "vintage" calculator as it is a design that havens back to the 80s but was really built with 90s tech.

It is a financial calculator that still very much has a place today & modern versions are still being sold. They can calculate unusual things such as mortgage payments, super easy to do percentage on unlike every other calculator. Another fun fact about these calculators was the first versions were were built with a saphia base instead of a silicon process for the chips. This is a process that is normally only reserved for space hardware & probably millarty tech.

The internal build construction is far better than any calculator I have taken apart from the 90s or even 80s. The use of gold plated traces is a nice touch, the chip is obviously a HP custom job & sadly not part of the saphia process as it is the more cost reduced version from the 90s, however the modern version is even cheaper & uses the dreaded Black Blob Chip.

Prinztronic 80

This is rather interesting, not meany calculators have the pedigree of being proper pocket calculators with panplex tubes, sure its a singal tube display & no option for external power. Runs on 4 AA battery's which is great as no evil Ni-Cad's in sight. The display shows errors by blanking the display & showing all the decimal places.

Has a Constant mode, but can limit some of the basic maths functions which is a little irritating, so you can't leave it on. It once again has an 8 digit panplex display, aka neon like the Nixies.

Opened you can see the use of space is quite clever with not much wasted space, quite true when you consider the tech available to the engineers of the time. The display is also nice & bright with big digits so is very readerble. There is also a singal 70s red LED. It is not very bright but does not use the standard 20mm plastic housing. It even have gold plated pins & is not very bright.

This is probably the smallest multiplexed panplex display I have ever seen, however interestingly these calculators do not all use the same chip sets, heres a link to the Vintage Calculator website where it uses a D2710. My example is completely different & seems to use LSI rather than a singal chip. So I could have an older version. Sadly we have not date codes in the calculator.

Sounddesign 8301

This is quite a cheaply constructed calculator for the 70s, interestingly the main power source is a battery with the option to power the unit from a mains AC power pack & not the other way round. This was a common option for handheld & pocket calculators of the era.

It has an 8 segment panplex display with a few indicators for over flow & even a segment that goes out when the battery's are two low. The on & off buttons are way to sensitive to use as a "pocket" or even a portable calculator, this one is better suited on an office desk on a day to day basis.

Opened up you can see it is quite cheaply constructed, you can also see where the external power goes in. The top half has the C cell sized battery's. Despite all the parallel rows of pins this calculator only uses one IC.

The back of the panplex display. It is a singal tube unit which is quite standard for panplex calculators. Shame these are not used any more.

Standard 4 function desk calculator of the early 70s (1972). It uses a TI TMS0103 chip set which is TI,s second generation of singal calculator chips. Interestingly if you film the display in slow motion you can see the calculation in progress. Aside form that is is a pretty standard calculator. There is also a version that had a Ni-Cad battery pack in as well so it would be technically portable.

The display used an a 9 digit panplex singal tube, the right most digit is used as the error indicator. Surprisingly for a mains powered calculator, the display is not driven perticulay bright which makes it hard to use under bring office lighting & impossible to use under sunlight coming in from the window.

I did use to use this calculator on my desk for a short period, until I got hold of & restored a much better IT desk calculator. The power connector was not a standard IEC plug, as I did not have the cable required I just installed an IEC socket.

This was one of the first vintage calculators I owned, found it in a skip in school, covered in rain. Yes I have had it for that long. One of the caretakers helped me grab it. It uses a 10 digit VFD & also has a printing function that blanks the display when it runs the printer. It is mains power only however has all the functions a modern 4 function calculator would have, memory, percentage etc. Interestingly it has an IF coil in there, usually only found in radio & video equipment.

Opened, you can see the main calculator IC uses a staggered pin pattern for a higher pin foot print. The date code on the chips is from 1984, so a little after the calculator race. Interestingly used a 3rd gen 10 digit VFD. The chip set is a NEC D1234G, nothing special. Even the Soviets used this pin format on some of there IC's, including calculator IC's.

This was my desk calculator in the office & replaced the Merlin. Since I now work from home, it is not my kitchen calculator, handy when backing etc. It is a 4 function 11 digit panplex display, the left most digit is used as a error display.

The underside of the PCB. You can see the repairs I have done on it as the keyboard was completely fucked when I got it. Was not easy to fix as it was a sealed unit.

The panplex display is the largest I own. It is also nice, bright & clear. As usual it is a ceramic & glass sandwich that the multiplexed units are constructed with.

The calculator chip is no surprise is a IT part. It is a TMS0106NC from 1974. You can also see the calculations being displayed, here's a slow mo.

Prinztronic X15

Pretty much a standard 4 function calculator. It uses a 8 digit bubble LED display. Does not try to calculate a divide by zero sum. Not to much to say about this one.

You can see the side of the bubble 7-seg LED display. Also the side of the main calculator IC, don't currently know the chip number or date of manufacture.

Another pocket calculator from CASIO with an 8 digit singal tube VFD. However unlike a lot of the other pocket calculators of the era it is a fully functioned calculator with things like square root & percentage. I have fixed it once, but it needs some more TLC.

This is also a singal chips calculator with an NEC chip set of UPD577C. Looks be from 1975. You can also see the rather nice 8 digit VFD tube which were commonly used by CASIO in this period. This calculator does not blank its display when running calculations: Video Here.

This is a rather nicely built hand held calculator which is quite modualer with the design. I don't know the exact year this one is from or the chip set though.

It has the smallest individual VFD tubes I have ever seen, don't even see them on eBay. Has 8 of them & three lovely 70s early LED's for status information such as errors & low battery.

The back of the PCB you can see was hand designed with all the nice curvy traces. Also the lack of a silk screen points to a basic, small production process.

Here you can see the 8 digit separate VFD tubes. Also three very vintage LED's that seem to be ceramic with gold plated pins, have a very nice deep red glow.

This is a quite rear Commodore calculator with an LED display, it is a programmable scientific calculator. I found this one in the skip at uni. Salvaged it, could not reach the rear case so had to jury rig one on from another dead Commodore calculator. The scientific functions are pretty standard.

Used it in a few uni exams & classes at uni.

This uses a singal chip that is a custom MOS chip. It is a MPS7561 chip set. Sadly being an early MOS chip, they are prone to chip rot so this calculator is on borrowed time, as anyone with a C64 PLA can tell you.

Pretty much a Sinclair Cambridge in everything but build quality & case design. Has all the same bugs & functions. It has an 8 digit 7 segment bubble LED display. Other than that, there is not much to say that has not already been covered.

The bubble LED display seems to be similar to the Cambridge model, even with 4-5 LED's per segment. Also glows with that lovely deep pure red that digital sensors just can't pick up.

The chip set CZL550 is the exact same as in the Sinclair Cambridge (C550), the only difference being is the chip is encapsulated in plastic. It even has the decide by zero bug, as seen here in slow mo.

Rear of the PCB is hand drawn but does have a silk screen. You can also see how cheaply it is constructed although not as bad as the Sinclair Cambridge.

This was one of the first graphing calculator models ever released, The 7000G was the first. Also fully programmable scientific calculator with a lot of functions that are not standard on calculators in the same class.

I originally got this for my uni exams as it could do some funky maths that just could not be done on a normal calculator. It has a nice UI that melds surprisingly well with the UI of a modern CASIO scientific calculator.

This is a standard 4 function calculator with all the modern creature comforts any one you would buy today, only this is 1980s. It has a 8 digit LCD & is one of the only two I have in the collection with LCD's

It was my parents house calculator for years & I saved it when the LCD started going dodgy. Since then I have been its carer.

This one is quite interesting for an LCD calculator internal. The first thing to note is the lack of the evil dreaded Black Blob Chip & a SMT package you can read the chip set of, NEC 8537K9 could also be a D1003G. One of the other things to note is the poloriser is not bonded to the LCD. The last part of note is the contact pads for the keyboard are not on the keypad its self, but on the rear of the case, making for a contact that has literally lasted decades.

Common for CASIO calculators of the era is the main PCB is a flex PCB, making it rather resilient do damage from any kind of abuse.

These reverse polish notation programmable scientific calculators have an interesting history. One was used as the backup earth re-entry computer for the Soviets using a custom program cartridge. That calculator was sold at auction for quite a hefty price.

Most of the cartridge ports are blank, aka fakes, however one is fully soldered up with pin headers, the other if you wanted to use it, you would have to solder on your own pin header.

The calculator has been completely reverse engineered & people have even written games for them. There is even a Elektronika MK-61 that is basically the same machine, just lacks an EEPROM.

The VFD is a nice example of Soviet displays that ranged back into the 70s. This being from 1992 shows that even when Russia finally became a "democracy" business just continued as normal for most people.

Quite uneek for a calculator, it has a non-volatile memory. An EEPROM of KP1601PP1, built in 1992, so quite a modern example. No other calculator I know of has ever had proper non-volatile memory.

The power supply for the VFD is completely modular, so it can be removed & repaired. The capacitors on these boards are known to go faulty, so I will keep an eye on these.

The chip set is unlabeled on the board its self, but every calculator came with a schematic, standard on old Soviet stuff. Also shows the Soviets were about a decade behind the rest of the world technologically.

Soviet Calculator PCB

I have no clue what calculator this PCB is from, maybe an old Nixie calculator. It was an eBay job that was going cheap & looked interesting. Interestingly it is from the late 70s, 1978 from the date code on the chips.

The PCB is of the usual Soviet construction quality, fiberglass PCB, no silkscreen & conformal coating. Even has connectors to interface with other parts of the system.

The calculator uses a five chip chip set of:
1. K145HK1P (Bottom Left)
2. K145HK1P (Bottom Middle)
3. K145HK2P (Bottom Right)
4. K145HK3P (Middle Right)
5. K145HK4P (Middle Middle)

Annoyingly there is bugger all on this board or the chip set online so I really don't have much on this board, It does make a nice door frame shelf queen.