Posted by
Dave wo2x on
May 09, 2012; 11:24am
URL: http://elecraft.85.s1.nabble.com/Connecting-my-Elecraft-K3-to-a-Drake-L-7-amp-tp7541893p7542594.html
Is he going to need a relay buffer such as the ARB-704 with that amp?
Dave
wo2x
-----Original Message-----
From: Jim Wiley
Sent: Wednesday, May 09, 2012 3:54 AM
To: Jerry Dwyer
Cc:
[hidden email]
Subject: Re: [Elecraft] Connecting my Elecraft K3 to a Drake L-7 amp.
Jerry -
The VOX connector is the transmit enable connection (PTT). The AGC
connection is for rigs that accept external ALC, and may not be needed
with the K3. Normal drive for full output is when 240 mA of grid
current is indicated when fully loaded.
Use the SSB setting on the plate switch for both CW and SSB. The lower
voltage / lower power setting is from when we were limited to 1000 watts
CW input, 2000 watts PEP for SSB. The amp will make about 1300 watts
(low bands) to 900 or 1000 watts (10 meters) if you have good tubes.
Simple adjustment procedure: watch the power output, tune for max using
the plate and load controls. The panel markings will get you close
enough to start. Recheck the grid drive to make sure you are not
exceeding 240 mA and you are good to go.
Both the tubes and the power supply are very forgiving, so temporary
overloads will be well tolerated. I have used both the L7 and its
earlier cousin, the L4B, for many years,. and never had a problem, even
when running full-blast key-down modes like RTTY.
You may wish to make a mod to the fan circuit to keep the blower turning
about half-speed at all times, instead of depending on the thermal relay
to start the fan when the amp is getting too hot. Simply wire a 300-ohm
/ 25-watt resistor across the thermal switch to accomplish this. The
fan will still go to full speed if needed, but mush less often, and the
amp will last much longer.
Be sure to observe normal safety precautions when working inside the
cabinet - disconnect the power completely, both from the wall outlet and
the PS from the amp, including the HV connection before opening the
cabinet.
- Jim, KL7CC
.
Jerry Dwyer wrote:
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