I have an older Icom PS15 power supply. I understand that when you use it
with a 706 which I am using, or any of the newer radios designed for it, it
should not turn on until the on button on the radio is pushed. This one,
when used with the 706, seems to turn on when it is connected to the radio
whether the on button is pushed or not.

Michael-

This may not be the same as an old Kenwood power supply made back in the 70s
for use with the TS-120S transceiver. That transceiver had an extra set of
contacts on its power switch, that were wired through the power connector. The
power supply (PS-30?) had a hard-wired cable with a pair of wires connected
across its internal switch. Either the switch on the power supply or the one
in the TS-120S would turn it on, as I recall. If you only turned on the power
supply's switch, the TS-120S wouldn't come on until its switch was also turned
on.

Many modern transceivers, including both Kenwood and Icom, use the same
connector as the old TS-120S, but there are two pins not used. If you used the
modern transceiver with the old Kenwood power supply, the transceiver's power
switch only switches the 12 volt line.

Does this discussion relate to the PS-15? If it has all six wires present in
its connector, then it may be the same. If two are missing, then it may have
some kind of sensor that detects a load and applies full power. If so, that
circuit may be malfunctioning in yours.

73, Fred, K4DII