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Connecting my Elecraft K3 to a Drake L-7 amp.

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Jerry Dwyer

Connecting my Elecraft K3 to a Drake L-7 amp.

I just got a good deal on a very clean Drake L-7 amp (2- 3-500Z tubes). I
was hoping someone might know how to connect them together. The amp has the
normal RF in and out connectors. It also has two rca connectors, one says
VOX and the other says AGC.

Thanks for any help

Jerry - NF9L

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Jim Wiley-2

Re: 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:

> I just got a good deal on a very clean Drake L-7 amp (2- 3-500Z tubes). I
> was hoping someone might know how to connect them together. The amp has the
> normal RF in and out connectors. It also has two rca connectors, one says
> VOX and the other says AGC.
>
>
>
> Thanks for any help
>
>
>
> Jerry - NF9L
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>

Dave wo2x

Re: Connecting my Elecraft K3 to a Drake L-7 amp.

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:

> I just got a good deal on a very clean Drake L-7 amp (2- 3-500Z tubes). I
> was hoping someone might know how to connect them together. The amp has
> the
> normal RF in and out connectors. It also has two rca connectors, one says
> VOX and the other says AGC.
>
>
>
> Thanks for any help
>
>
>
> Jerry - NF9L
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>

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Jorge Diez - CX6VM-2

Re: Connecting my Elecraft K3 to a Drake L-7 amp.

In reply to this post by Jim Wiley-2

Hi Jerry,

You can place an external fan on top of the power supply also.
It became very very hot in extreme conditions.

73,
Jorge
CX6VM/CW5W

-----Mensaje original-----
De: [hidden email]
[mailto:[hidden email]] En nombre de Jim Wiley
Enviado el: Miércoles, 09 de Mayo de 2012 04:55 a.m.
Para: Jerry Dwyer
CC: [hidden email]
Asunto: 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:
> I just got a good deal on a very clean Drake L-7 amp (2- 3-500Z tubes). I
> was hoping someone might know how to connect them together. The amp has
the

> normal RF in and out connectors. It also has two rca connectors, one says
> VOX and the other says AGC.
>
>
>
> Thanks for any help
>
>
>
> Jerry - NF9L
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>

Rick Stealey

Re: Connecting my Elecraft K3 to a Drake L-7 amp.

In reply to this post by Dave wo2x

No. Definitely not. But he might need to set TX DLY to 20. That delays the
start of RF a little to give the relay in the amp time to close. Symptom that
it needs that adjustment is a little arc or "spitting" when the first bit
of RF is generated. My L4B was doing that, and after moving TX DLY
to a value of 20 it was ok. Using an external relay makes matters worse.

Rick K2XT

> Is he going to need a relay buffer such as the ARB-704 with that amp?

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ke9uw

Re: Connecting my Elecraft K3 to a Drake L-7 amp.

In reply to this post by Jerry Dwyer

The AGC is an input for letting the transceiver control the output power of the L7 which you don't need if you adjust your transceiver to a low output suitable for driving the L7.
The VOX is the keying control for the amp. Pull low (ground) to transmit.

Chuck, KE9UW
aka Jack, BMW Motorcycles BMWMOA #224

________________________________________
From: [hidden email] [[hidden email]] on behalf of Jerry Dwyer [[hidden email]]
Sent: Wednesday, May 09, 2012 12:55 AM
To: [hidden email]
Subject: [Elecraft] Connecting my Elecraft K3 to a Drake L-7 amp.

I just got a good deal on a very clean Drake L-7 amp (2- 3-500Z tubes). I
was hoping someone might know how to connect them together. The amp has the
normal RF in and out connectors. It also has two rca connectors, one says
VOX and the other says AGC.

Thanks for any help

Jerry - NF9L

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Chuck, KE9UW

Jim Wiley-2

Re: Connecting my Elecraft K3 to a Drake L-7 amp.

The AGC connection is an OUTPUT from the amp to the transceiver, not an
input.

Its purpose is to lower the gain, and thus the power output from the
exciter when the amp is overdriven.

On the L4B / L7 series amplifiers, the way to set it to adjust the amp
for max output, then back of the AGC / ALC adjustment control until the
amp just begins to reduce power. However, as several have said, it may
not be needed when driving the amp with a K3. The operator can see in
an instant which way the control works by rotating it from one limit to
the other, and then adjusting it as per the first sentence of this
paragraph. .

Some on the air checking, as well as using a scope to monitor the
transmitted output waveform will help the operator determine whether or
not AGC / ALC is needed.

- Jim, KL7CC

hawley, charles j jr wrote:

> The AGC is an input for letting the transceiver control the output power of the L7 which you don't need if you adjust your transceiver to a low output suitable for driving the L7.
> The VOX is the keying control for the amp. Pull low (ground) to transmit.
>
>
> Chuck, KE9UW
> aka Jack, BMW Motorcycles BMWMOA #224
>
> ________________________________________
> From: [hidden email] [[hidden email]] on behalf of Jerry Dwyer [[hidden email]]
> Sent: Wednesday, May 09, 2012 12:55 AM
> To: [hidden email]
> Subject: [Elecraft] Connecting my Elecraft K3 to a Drake L-7 amp.
>
> I just got a good deal on a very clean Drake L-7 amp (2- 3-500Z tubes). I
> was hoping someone might know how to connect them together. The amp has the
> normal RF in and out connectors. It also has two rca connectors, one says
> VOX and the other says AGC.
>
>
>
> Thanks for any help
>
>
>
> Jerry - NF9L
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>