Printer help?

From: der Mouse <mouse_at_Rodents.Montreal.QC.CA>
Date: Thu Sep 9 23:29:56 2004

>> However, the selftest button does not work; as far as I can tell it
>> does nothing at all. I even tried holding it in for some 15-20
>> seconds and it still did nothing [...]
> Now this is weird, I have no explanation for it. It's supposed to
> continuously print pages of vertical lines for as long as the switch
> is down. Perhaps one of the damaged PCB traces went to this switch?

I suppose it could be, but the damage is off in a corner far away from
anything else, and most definitely on any even vaguely direct route
between that button and anything. It would take an almost deliberately
perverse PCB layout for an etch run carrying that signal to have been
hit by the damage. (If we normalize coordinates with (0,0) at the
lower left and (1,1) at the upper right, the test switch is at perhaps
(.05,.333) and the damage is at something like (.9,.07). The whole
triangle (1,0)-(1,.4)-(.6,0)-(1,0) contains nothing that looks like
logic to me, except perhaps a few discrete transistors.)

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Received on Thu Sep 09 2004 - 23:29:56 BST