The Ten-Tec supplies 252 and 262 did not incorporate a "crowbar" circuit to
protect the rig from a fault which would supply too great a voltage to the
rig. This can happen if the pass transistor shorts out and the power supply
output rises to 24 or 25 volts.
Ten-Tec later made a small circuit board available as an inexpensive option.
This was called the OVP, overvoltage protection circuit. The small board
was about 1 x 2 inches and holds a fuse, an SCR and a zener diode as I
recall. The instructions that came with it said to mount it inside the back
panel of the supply and to cut the large red wire before it went to the
output leads or connector, hooking the two ends created by the cutting to
two solder points on the OVP circuit board.
My suggestion is that if you have one of these supplies you check to make
sure it has that little board inside. It is more important than you might
think.
73, Mike N4NT
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