> Well, when the amp is not being transmitted on ; just idling. 125 ma is
> correct.
::There are two kinds of idling: One is when the amp is turned on,
and in the operate position after the warmup is completed, but the amp is
not keyed into the "transmit" mode. The other kind of idling, what I call
"idling," is when the amp is on, in operate, and keyed up for transmit, but
no RF drive is applied. In other words, "transmitting" but providing no
output because there's no drive signal. THAT is the "idling" that Alpha
refers to when they discuss "idling current."
If the amp is drawing current even before the T-R relay is keyed,
there is indeed something seriously wrong.
> This sounds like too much idling current to me. And the tubes
> get pretty warm
::Yes, well, 125 mA @ 2500V or so is over 300W. That would make
some heat, for sure.
> as I can tell from heat coming out of exhaust port. I
> can stop heat and current by switching either switch to stand by or to
> cw/tune. The current goes to zero; grid and plate . Turn switch to
> operate and grid current comes back and plate current also.
::There should never be any grid current at all if there's no drive
signal applied. It honestly sounds to me like you've got a bad
3CX800A7...I've never seen one of these draw any grid current in "standby"
unless it had an internal problem. Maybe one of the tube experts (Rich?)
can make further comment on this.
> I am not
> transmitting at any time. The manual says that 15 ma grid current in the
> SSB mode while idling is to stop switching nois
>
::I don't remember that statement, exactly, but then I haven't read
the 374 manual in years. Normally, keeping the idling current low in the
absence of a drive signal simply lowers your electric bill, keeps the tubes
a bit cooler -- I don't see how "noise" comes into it, since the amp should
only draw plate current (any plate current) when it's in the "XMIT" mode, in
which case you're not normally receiving, you're transmitting. But
anyway...
> Anyway, I have been
> working on control board and found a few problems and it seems I have
> another. I am considering buying a good control board for same amp.
>
>
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