Re: recent HP 35 "Red Dot" on Ebay Message #4 Posted by D. Taylor on 29 Feb 2012, 5:56 a.m., in response to message #3 by aj04062
I'm at the limits of my knowledge here - but logically if rows 3 & 4 are well isolated when the two boards are attached then it's not a problem of a short between those lines anywhere on either of the two circuit boards.
I guess you could check the resistance to ground on those two lines (R3 and R4) with the mainboard disconnected from the keyboard (check it on both the mainboard and the keyboard) to see on which board R3 has the low resistance to ground. If it's on the keyboard then maybe it is a problem with a trace on the keyboard, but more probably it's on the mainboard and it's in the chip, because 50Kohms is not a short unless it's going through a 50Kohm resistor on the circuit board.
Like I said, I'm at the limits of my knowledge here, in case anyone else wants to step in!
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