Okay, now I get it. Any voltage about one PN junction forward breakdown
lower than +REG will turn on Q1. So when turning the Omni VI on, zero
volts will turn on the 9420. And when the 9420 is up, the 13.6 it
produces is still low enough that Q1 stays turned on. It is still
unclear to me how the 9420 would ever shut down after the Omni VI power
switch is turned off. Maybe with no load the power supply voltage will
rise high enough to let Q1 shut down.
The lables on my schematic for the 9420 show where the 3 non-ground
wires of the transceiver connector go, to HI I, LO I and PWR ON. Putting
a "load" (perhaps a short to ground) on the PWR ON lead would turn on
Q1, and then everything that happens when the amplifier power switch
connects the other PWR ON to the +REG would happen just the same. What
is unclear to me is how the Omni VI wiring does this.
It looks to me like the only way to turn the 9420's 4 separate power
supplies on it to apply +13v to pin 3 of the 12-pin plug.
But that doesn't make much sense because then the Herc would always
have to
be on before you could turn the Omni VI on. Ten-Tec usually does
logical
stuff so there must be some trick in how the 4-pin is wired.
Unfortunately
there's no description and the drawings are vague (showing only 1 line
between the 4-pin plug and the P.S.).
The transceiver "power on" is activated by connecting a load to this
"power on" lead. The text does not say what they mean by a load, and
it does not say just to ground it. I'll look at my Omni VI manual
and see what it connects to pin 3.
I am not getting this. I does not help that my Omni VI manual does
not have pin numbers on the DC Power Input Board schematic. I don't
see how the power switch on the Omni VI can turn the 9420 on and off.
It looks like just plugging in Omni VI into the 9420 would turn it
on, regardless of the power switch postion. I have never tried using
the 9420 to power the Omni. Never made up a cable to do it. Still I
would like to understand this circuit, in case I ever want to use it
that way. Anybody out there who can clarify this?
DE N6KB
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