From: Garey Barrell 
Subject: Re: [drakelist] ALC ?


Garey Barrell  made an utterence to the drakelist gang
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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/>



Abqcooks{at}aol.com wrote:

>Abqcooks{at}aol.com 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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On Behalf of Garey Barrell 
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