Commodore 500E or Casio 101E documentation?

[Santo Nucifora]

Hi All,

I just acquired a Commodore 500E which is a rebadged and slightly different Casio 101E.  It is not in working order.  I get a few decimals light up briefly and some nixie tubes flashing when switching it off, but that's it.  I haven't yet dug into the power supply and hope it's something there.   Could ne in the logic but I wanted to confirm voltages first.

Would anyone happen to have technical docs or schematics?  I know it's a long shot but it's worth a try.  Here is a picture for the fans.

[M. S.]

Only found find this one: 

https://ia800901.us.archive.org/20/items/commodore-500-e-operators-instruction-manual/Commodore_500E_Operators_Instruction_Manual.pdf

Op vr 13 feb 2026 om 17:06 schreef Santo Nucifora <santo.n...@gmail.com>

--
You received this message because you are subscribed to the Google Groups "OldCalculatorForum" group.
To unsubscribe from this group and stop receiving emails from it, send an email to oldcalculatorfo...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/oldcalculatorforum/CAO6%2BCm6CN-zgHxbi8H7avQj%2BjTZxKjN%2BU_FvWGvfpt941NriZQ%40mail.gmail.com.

[Santo Nucifora]

Thank you all the same but I was aware of that one and Dave McMurtrie's video on YouTube.  I am hoping someone might have a technical manual or schematics.

Santo

To view this discussion visit https://groups.google.com/d/msgid/oldcalculatorforum/CANGG9FCaRo%3DJgen4k1W-m2WOsOkvgDW9pYOzSGDPj16jzYcCnw%40mail.gmail.com.

[Patrick Souty]

Hello,
have a look to the Casio AL1000 technical data in the pdf attached.
This is extracted from http://madrona.ca/e/eec/calcs/CasioAL1000.html and pictures of boards inside look very similar to what can be found on caluseum.com for the Commodore 500E.

[Santo Nucifora]

Thanks for the reply Patrick.  They are actually quite different after looking over the parts of the boards I can see.  

Luckily I have some good news.  After replacing one capacitor in the power supply that seemed marginal to me, it sprang to life and I have a display and working keys.

However, calculations are not working right.  I enter "123 =" and I should see "123" but I am seeing "101".  Any other operations are just wrong so it definitely needs more work but at least I have more to work with.  I'll just have to go through each board and check the individual components, one by one.  With schematics or technical documents, I could have narrowed it down but I'm okay with checking all the boards.  To be honest, I am happy to have gotten this far.

Thanks again guys.

Santo

To view this discussion visit https://groups.google.com/d/msgid/oldcalculatorforum/d6d7f26b-9d9c-48dd-b402-2a4395860c32n%40googlegroups.com.

[Patrick Souty]

Hi Santo,
Well done, I am glad to see that such an old machine is still alive, at least it's nice display.
As all digits and all keys seem OK, but entering "123 =" gives "103", I think this is at least the symptom of a failure inside the core memory.
You might investigate this in first.

[Rick B]

Beware. 

Architecturally, the AL-1000 and the Casio 101E/Commodore 500E are very different.  

The AL-1000 uses magnetic core memory for its register storage, which changes the way the machine operates considerably as compared to the Casio 101E/Commodore 500E.  The "E" (I'll use this designation to denote the Casio 101E/Commodore 500E calculators) machines use chains of flip flops organized as shift registers for working register storage, with each bit of a register operated upon as it shifts out the end of the chain of flip flops.  The "E" machines have a true bit-serial architecture, operating on one bit at a time.   The AL-1000 operates on four-bit BCD quantities at a time, with an ALU that performs a parallel operation on two four-bit BCD numbers.   The AL-1000 also uses this four-bit parallel architecture to its advantage to create the first Casio calculator that multiplexes its display rather than having separate display decoder/driver circuitry for each digit in the display.   With multiplexing, one decoder/driver circuit is "timeshared" across all of the digits, with each digit lit up for a short period of time, one by one, done fast enough that the display appears to the eye as continuous.   The "E" calculators continually drive all digits of the display all the time, using a whole lot more components to drive the display than the AL-1000.   The digit-at-a-time architecture and multiplexed display significantly change the control logic of the AL-1000 as opposed to the earlier "E" calculators, which were based mainly on the logic of Casio's first electronic calculator, the Casio 001, but using Silicon transistors rather than Germanium.  The fact that the AL-1000 is also programmable adds additional complexity to the AL-1000 that doesn't exist in the "E" calculators, which could also complicate trying to apply the principles of operation between it and the "E" calculators problematic.

Using the logic diagrams of the AL-1000 that Brent H. so painstakingly reverse-engineered from an AL-1000 that he rescued could be quite misleading when trying to diagnose the Commodore 500E.  While studying the logic of the AL-1000 is a great way to understand the principles behind Casio calculators that came after the AL-1000, it is not necessarily a worthwhile study when trying to understand the logic of the Casio 101E/Commodore 500E.   That's my opinion having restored three AL-1000's to operation, and repairing  the Commodore 100E in the Old Calculator Museum, finding that the two machines are quite different in design.

As an aside, I'd be interested in finding out the serial number of the Commodore 500E that is the topic of this thread.   I keep a list of serial numbers that I can get for each machine to help determine if there is any pattern to the serial numbers, and if that pattern can perhaps help provide clues as to when the machine was manufactured, and perhaps an approximation as to how many machines were produced.

Sincerely,

Rick Bensene, Curator

The Old Calculator Museum

https://oldcalculatormuseum.om

Beavercreek, Oregon   USA 

To view this discussion visit https://groups.google.com/d/msgid/oldcalculatorforum/d6d7f26b-9d9c-48dd-b402-2a4395860c32n%40googlegroups.com.

[Santo Nucifora]

Thanks Rick.

My serial number is 50978.  Dave McMurtrie, who did the Commodore 500E video here https://www.youtube.com/watch?v=pSnOCFKQ5Os has a serial number of 50620.  I didn't see any components in the power supply with definitive dates on them that jumped out but as I dig into it, I'll see if i find anything.  Dave's video has the receipt of the person who bought it in the video but who knows how long it was manufactured before being sold.

Hope this helps a little.

Santo

To view this discussion visit https://groups.google.com/d/msgid/oldcalculatorforum/CAMbJjuR6tj%3DTM-eYk4FC1WJmtW68e_5R934ZH%3DkVb8StXu%2BUOw%40mail.gmail.com.