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S > SIGNETICS > Instructor 50   

Instructor 50

The Instructor 50 was a small system designed to teach the use and programmation of the Signetics 2650 CPU. But it was also a real micro-computer with a tape interface to save and load programs, and a S-100 compatible expansion bus.

It actually belonged to a second generation training computers: unlike its predecessors, it wasn't just a raw electronic board, but offered a real plastic case, S-100 bus, tape-interface, etc....

The built-in display was only a eight-digit, seven-segment LED display... When turned on it displays "HELLO". The keyboard was made of an hexadecimal keypad (16 keys) and function keypad (12 keys). Interaction is also made through 8 parallel I/O switches and their corresponding LEDs.

The only software built-in the system was the monitor (called User System Executive or USE), used to program the Instructor 50. Of course, programmation was made in hexadecimal through a simplistic assembler.

The 2 KB ROM was used to store the monitor. RAM was 640 bytes, but 128 bytes were used by the monitor, leaving 512 bytes for programmation. But having 14 address lines, the 2650 CPU was capable of addressing 32K bytes !

We need more info about this computer ! If you designed, used, or have more info about this system, please send us pictures or anything you might find useful.
Please consider donating your old computer / videogame system to or one of our partners from anywhere in the world (Europe, America, Asia, etc.).

Special thanks to Justin Tyler who donated us this computer !


Adress for the Signetics 2650 instructions manual here :

Sunday 26th September 2021
Usram (France)

I''m the proud owner of a Signetics Instructor 50. I got the machine running with an AC power supply, but the heat sink of the old fashioned 7805 got pretty hot, so I switched it off. I don''t have the original power supply unit, but looking at the schematics, I guess it should be 8V AC? In the schematics I see a 5V (DC?) line and an 8V (AC?) line. Does anyone have the original adapter and can info and/or pictures be shared?

I have 6 thick Philips manuals, but they are all in Dutch (no problem for me of course). Happy to share.

Instructional manuals can easily be found through Google, in English.

I saw the post from 2016 in this forum about someone who destroyed the machine by mixing up 110V and 220V (actually it is 230V since 1982 or so...), but actually I don''t understand how that could have destroyed the machine, I''d say only the power supply is gone (or worst case the 7805 and maybe a few other components).

Wednesday 6th December 2017
George (Netherlands)

If anyone has manuals, parts or expansions for the Instructor-50 in Europe please contact me, or leave a message here. I''ve got mine up and running but no manuals. Mine came from a lot of 70''s computer hardware from the Philips NatLab in Eindhoven.

Tuesday 11th April 2017
Nick (Netherlands)


NAME  Instructor 50
TYPE  Professional Computer
YEAR  1978
BUILT IN LANGUAGE  Hexadecimal Monitor
KEYBOARD  1 hexadecimal keypad + 1 function keypad
CPU  Signetics 2650
SPEED  895 kHz
CO-PROCESSOR  Signetics 2656
RAM  128 bytes (used by the monitor) + 512 bytes (free for the user)
ROM  2 KB (monitor)
TEXT MODES  LED display - 1 line of 8 characters
SIZE / WEIGHT  35 (W) x 25 (D) x 7.5 (H) cm / 1.1 kg
I/O PORTS  Tape interface, S100 compatible expansion bus
POWER SUPPLY  External power supply (5V or 8V depending on models)
PRICE  350$ (USA, 1978)

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