Garey Barrell <[EMAIL PROTECTED]> made an utterence to the drakelist gang ---------------------------------------------------------------------- Jim -
I really don't know what level of negative ALC bias is required for the T-4(any) transmitters. It is a high impedance input, (1 Meg,) and is applied directly to the grid of V2, the IF Amp. -10V should be enough to cut this stage off, so it should work. If you have a 9V battery and a pot, it would be simple enough to measure the ALC sensitivity. Also, keep in mind that the ALC is turned OFF for the CW and AM modes.
In any event, Pin 3 of the power connector IS the ALC input, and it expects a negative voltage, the more negative the voltage, the more the T-4(any) output is reduced.
The AC-4 was originally supplied for the TR-4. The single small "pigtail" RCA phono cable originally was the speaker output for use with the TR-4. This allowed the TR-4 to be plugged into a mobile mount with no additional connecting cables required.
The T-4X was originally sold with the AC-3 power supply. The AC-3 had no ALC or VOX connector at all, but the power connector had the pigtail for the speaker in the TR-3. There is at least one AC-3 out there somewhere that has the pigtail rewired to Pin 3!
73, Garey - K4OAH Atlanta
Drake C-Line Service Manual <http://hr99.home.mindspring.com/R-4C_Servicez/>
[EMAIL PROTECTED] wrote:
[EMAIL PROTECTED] made an utterence to the drakelist gang
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I have a T4XB driving an Ameritron Al-80B amp and would
like to get the ALC hooked up. The T4XB manual is very brief
on the ALC hook up so I'm not sure I get the picture.
The manual states that an amp providing a negative going
alc voltage can be hooked to pin 3 of the power connector.
I have 3 AC-4 power supplies but only one of them has
a female phono jack that is marked "xmtg alc". Am I to assume
that is "pin 3" ? If that is the correct place to feed
alc voltage from the amp, it does not work. Course my amp
is providing 0 to -10vdc alc and perhaps the T4XB needs
more of a negative swing than that ? The T4XB manual
doesn't state what amount of negative voltage is needed.
And perhaps I am not feeding that alc voltage into the T4XB
in the correct place ? Not wanting to risk my T4XB on guesswork and experimenting, I figured that someone here
might enlighten me. Also, I wonder what is the function of the female phono connector that stubs off the AC-4 power connector.
Long as I'm here I would like to toss in a kind word for the gentleman at www.radiocovers.com ......
I just received a set of his covers for my Twins and my TR-4
and they are as advertised and more. Excellent quality at
a very reasonable price. Sure dresses up the Drakes in style
while keeping the dust out.
OK....thanks guys....any ALC ideas welcome.
It's a sunny warm morning in NM after a colorbursting sunrise.
73 jim N5KY
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