Reverse Engineering 15 yr old electronics
dave04a at dunfield.com
Fri Nov 11 20:42:31 CST 2005
>One thing I forgot to mention in my last message. Get a good continuity
>tester. 'Good' means one that is not fooled by diode junctions (and
>preferably not by low-ish resistors), one that doesn't supply enough
>voltage or current to damage anyting, one that beeps, and one that beeps
>quickly (you want to be able to 'stroke' a probe along a line of pins to
>see if a given connection goes to any of them).
A useful trick I sometimes use when I have trouble following a connection
(especially those which "disappear" into a multi-layer board). If you just
can't figure out where a signal goes - cut squares of tinfoil, and press
them against sections of the board with a firm sponge (something with
enough give to let the foil seat against all the pins). Then using a good
continuity tester such as Tony describes, you can quickly cover large
areas to quickly narrow down where exactly a signal is located. (use foil
squares sized as needed).
Obviosuly you do not want the board powered at all - insure that caps are
discharged, batteries removed etc.
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
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