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Missing chip on Adam Printer Controller Board


Milli V
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I am going through some parts printers and I have one that works with the exception the print wheel just vibrates and never resets- I switched heads and it is not the head but the controller board. Looking at 4 boards I have I see that U3 is just an empty socket on the one I question but the others have a chip soldered in ( ignore the crazy wires on the one - no clue ). I don't know what this chip does but could it be the reason for the problem?

 

Milli

 

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This is what the part is. I ordered some for .50 each - maybe I can fix the other printers too, they all have an issue with either the printhead motor or the carriage motor

 

The ULN2001, ULN2002, ULN2003 and ULN2004 are high voltage, high current Darlington arrays each containing seven open collector Darlington pairs with common emitters. Each channel rated at 500 mA and can withstand peak currents of 600 mA. Suppression diodes are included for inductive load driving and the inputs are pinned opposite the outputs to simplify board layout.

The versions interface to all common logic families: ULN2001 (general purpose, DTL, TTL, PMOS, CMOS); ULN2002 (14 - 25 V PMOS); ULN2003 (5 V TTL, CMOS); ULN2004 (6 - 15 V CMOS, PMOS).

These versatile devices are useful for driving a wide range of loads including solenoids, relays DC motors, LED displays filament lamps, thermal printheads and high power buffers.

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This is what the part is. I ordered some for .50 each - maybe I can fix the other printers too, they all have an issue with either the printhead motor or the carriage motor

 

The ULN2001, ULN2002, ULN2003 and ULN2004 are high voltage, high current Darlington arrays each containing seven open collector Darlington pairs with common emitters. Each channel rated at 500 mA and can withstand peak currents of 600 mA. Suppression diodes are included for inductive load driving and the inputs are pinned opposite the outputs to simplify board layout.

The versions interface to all common logic families: ULN2001 (general purpose, DTL, TTL, PMOS, CMOS); ULN2002 (14 - 25 V PMOS); ULN2003 (5 V TTL, CMOS); ULN2004 (6 - 15 V CMOS, PMOS).

These versatile devices are useful for driving a wide range of loads including solenoids, relays DC motors, LED displays filament lamps, thermal printheads and high power buffers.

Sure sounds like it needs that specific chip. What is NOT surprising is the fact that all these chips are 30+ years old and are bound to start failing just from old age.

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Hard to say for sure if that missing chip is needed on that controller board what with all the revisions that these boards went thru in the span of only a couple years and they definetely weren't all documented. You are probably used to seeing a lot of jumper wires on the different revision boards and even the same revision boards.

 

The odd thing here is that there is a socket placed on this board in question which Coleco didn't use a lot to save on time and money, so this could have been done after the fact by them, Honeywell Service Centers, one of the aftermarket repair services or just the end user in an attempt to fix a problem.

 

Trial and error is the only route here. Acquire that chip and install in the socket to see what happens. Also, as you have been doing, takes pics and document all the systems you have been repairing/refurbishing for your own future reference.

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