|Re: 9810 on TAS|
Message #20 Posted by Tony Duell on 1 July 2011, 4:14 a.m.,
in response to message #19 by David Ramsey
Yes, you are absolutely correct. I have said many times that the most important piece of test gear is your brain :-)
More seriously, all the multimeter, logic analyser, 'scope, etc do is enable you to gather evidence as to what the machine is doing. You can't directly see electrical signals, and you can't directly interpret any signal at 8MHz, so you need test gear to be able to follow what the signals are doing.
However, IMHO the _only_ way to find a fault goes like this : Understand what the machine should be doing, make measurements to find out what it is doing, then work out why the 2 are different.
This may be straightforward (for example if you're missing some segments in one row of the display, I'd home in on the driver chips for that row), it may be complicated (a totally blank display can be caused by a fault in the CPU, memory, PSU, display driver, etc). But only by goinging logically through the machine will you find the fault and cure it.
Making random changes, boardswapping and the like, will get you nowhere fast.