Roger Weichert wrote:
> Other than not having anything to communicate to the board with, I
> have everything else working  ...  so I'll take a stab at a value,
> fit a couple of TVS's, send it back and see what happens.

Take the TVS that measured open with the ohmmeter and put a 1Kohm resistor
in series with it.  Now connect a variable power supply to the combination
and monitor the voltage accross the TVS.  At some point the TVS voltage will
stay roughly flat as you increase the power supply voltage.  This should
happen the same in both directions, but it's also possible for a TVS to be
half fried and only clamp in one direction.  Try both directions therefore.
If you get close to the same answer each way, then that's the voltage
rating.  You should be able to replace the busted one with a similar or
slightly bigger size part at the same voltage rating.

Power dissipation is mostly a function of the package, so if the replacement
has the same voltage rating and the same package, then it should be roughly
equivalent.  Since one of the existing TVSs blew out, it wouldn't hurt to
replace both with a slightly bigger part, since that should take a little
more energy before frying.


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