25 Sep
2002
25 Sep
'02
9:30 a.m.
On Wed, 25 Sep 2002, Patrick Rigney wrote:
You would have to have a monster zener to be safe, probably 50 W or
so. Those arent that common. A crowbar circuit stolen from another supply or a
home made one would be better than a zener.
Instead of a crowbar (that usually use SCRs), You could also use a
5.6v or so shunt regulator made with a big (20A) power transistor and a 5V
10W zener...
Peter Wallace
Better still,
if you are testing the cards one at a time with an external
supply, tack on a 5V (set to 5.5 or so) crowbar on the output side of the
local 5V regulator -- no cut traces, only tacking on 2 wires
temporarily...
Peter Wallace
Peter, yeah, this seems like an easy approach. Question: could a simple
6.2V Zener be installed reverse-biased from the 5V regulator output to
ground? Seems like you'd want inline fuses between the unregulated supply
and the backplace as well for this kind of test...
Patrick