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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 22nd Sep 2022, 1:37 pm   #1
pmmunro
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Default Astec International Device in Commodore SR4190R Calculator

Can any one help with infromation about the device in the image below please?

I believe that it is a DC-DC converter and it is used in a Commodore SR4190R with LED display, dating from the 1970s. There are the characters "7648" on the back, but I would expect that this is a date code rather than a type number. Any other markings are too faint to be read or even to be sure they are markings.

It is a three wire device and the most basic information I would like is the colour coding for the leads. It would also be useful to know why it is used; the calculator was intended to be powered by three Ni-Cad cells or from its 6V charger.

PMM
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Old 22nd Sep 2022, 1:57 pm   #2
SiriusHardware
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Default Re: Astec International Device in Commodore SR4190R Calculator

ASTEC were most commonly associated with power supplies and modulators, so I think your guess that this unit is a DC-DC converter is a good one.

I am going to take a wild guess and suggest to you that this converter takes whatever voltage it receives on the red wire and outputs an equivalent negative voltage on the blue wire, the black wire being connected to circuit 0V/GND of course.

A few of the microprocessor ICs of the mid seventies period had oddball power supply requirements which sometimes included negative supply voltages.
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Old 22nd Sep 2022, 2:25 pm   #3
ronbryan
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Default Re: Astec International Device in Commodore SR4190R Calculator

I think that the 4190 VLSI calcuator chip (Mostek MPS7200) was pmos, which needed something like a -30V supply, hence the need for the converter.

The type number of my Aztec DC-DC converter is AA4082, with the same date code of 7648.

I've attached a photo of the interior of my SR4190R showing where the wires go on the pcb. Were you hoping to identify the voltages applicable to each lead colour, or is the above sufficient information?

Ron
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Last edited by ronbryan; 22nd Sep 2022 at 2:43 pm. Reason: Chip number added
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Old 22nd Sep 2022, 4:08 pm   #4
pmmunro
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Default Re: Astec International Device in Commodore SR4190R Calculator

Ron,

As you've guessed the first question was if the wires, which were broken off at the PCB, were back in the right place - they were, so thanks very much for answering that and for taking the trouble to send good clear photographs; it's a very great help.

Knowing the intended voltages on each lead would be a nice extra.

The other information will be useful too and, I hope, allow me to get this calculator going again.

PMM
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