20 Mar
2007
20 Mar
'07
10:22 a.m.
On 20 Mar 2007 at 10:08, dwight elvey wrote:
One could also use a pair of power zeners. Wired back
to back, they
make a fare protector. Actually, in your case, a single zener might be
better. It would clamp the voltage in one direction to the normal
operating level while allowing only a diode drop the other direction.
Dwight
One could also use both, since the purpose of each differs. The
zener will protect the unit from inadvertent moderate overvoltage and
reverse polarity errors. The MOV will protect the unit against high-
current transients.
I wonder if the MOV's original intention was to protect the unit when
installed in a leased-line arrangement (i.e., no modem). Induced
high-current transients are not uncommon in such setups.
Cheers,
Chuck