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Martin Roboscan 812 control board issue


FoggyJames

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Hi Kevin,

 

Many thanks for your reply.

 

Do you think the address lines on the 'bad' unit look alright? I thought I might have been on to something then - not that I know, really!

 

Would you advocate changing all of the flip-flops, plus the demux? I've just looked it up, and the component cost is well under £5 for the lot (6x 374, and a single 238), so I figure I might as well get the lot swapped while I'm bribing my colleague with beer money...right? :)

 

cheers

 

James

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  • 2 months later...

As per my experience all of the wheel steppers are supplied by a nominal 12V, unregulated supply which is then used to supply the 7805. It might be worth checking the input to the 7805, which is a convenient place to identify the 12V rail, for excessive ripple. It also appears on pin 10 of both of the ULN2803s if that is easier to get at. Do the mirror motors move at all?

They use the other supply rail (nominally 24V). If not then the only common components are the MPU, which you've already swapped, the crystal and its capacitors, and the 74HCT238.

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