Collins 30L-1 amp with the K3

[Butch Schartau]

I want to use a Collins 30L-1 amp with my K3, when I plug the 30L-1 amp
control cable into the K3 KEY OUT jack, the 30L-1 keys.  The 30L-1 is keyed
by grounding it's key line (pulling -160 DC to ground).  The K3 specs says
+200 VDC, at 5 amps, I guess the K3 does not like the minus voltage on the
30L-1 key line, any suggestion other than an external relay?

Butch K0BS
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[Don Wilhelm-4]

Butch,

The HEXFET used in the K3 KEY OUT circuit has a diode to protect against
negative voltage excursions.  I do not know how much negative voltage it
will stand, but it is possible you exceeded the limit.  That diode
conducting is the reason your amp was keyed every time you plugged it
into KEY OUT.

You can check to see if the K3 KEY OUT still works OK with an ohmmeter -
you should have an open circuit during receive - then use TX TEST and
again check the resistance at KEY OUT - it should be near zero.

Yes, an external relay would be a good solution, or modify the amplifier
in some way to key it by grounding a positive voltage.

Checking the specs for the devices on both ends of the cable before
plugging that cable in is always a good idea.

73,
Don W3FPR

Butch Schartau wrote:
> I want to use a Collins 30L-1 amp with my K3, when I plug the 30L-1 amp
> control cable into the K3 KEY OUT jack, the 30L-1 keys.  The 30L-1 is keyed
> by grounding it's key line (pulling -160 DC to ground).  The K3 specs says
> +200 VDC, at 5 amps, I guess the K3 does not like the minus voltage on the
> 30L-1 key line, any suggestion other than an external relay?
>
> Butch K0BS
>  
>
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[Eric Swartz - WA6HHQ]

HiButch,

Do not hook the K3 directly to the 30L-1. The K3 only switches positive
voltages to ground on TX. Hooking up a negative voltage will not work
and may damage the Keyout keying transistor.

An external relay or a negative voltage keying transistor buffer are the
best ways to do this.

Butch Schartau wrote:
> I want to use a Collins 30L-1 amp with my K3, when I plug the 30L-1 amp
> control cable into the K3 KEY OUT jack, the 30L-1 keys.  The 30L-1 is keyed
> by grounding it's key line (pulling -160 DC to ground).  The K3 specs says
> +200 VDC, at 5 amps, I guess the K3 does not like the minus voltage on the
> 30L-1 key line, any suggestion other than an external relay?
>
> Butch K0BS
>  
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[P.B. Christensen]

> I want to use a Collins 30L-1 amp with my K3, when I plug the 30L-1 amp
> control cable into the K3 KEY OUT jack, the 30L-1 keys.  The 30L-1 is
> keyed
> by grounding it's key line (pulling -160 DC to ground).

Butch:

Consider this alternative:

http://home.att.net/~jacksonharbor/keyall.htm

It's optically-isolated and keys substantial voltage of either polarity,
including AC loads up to 2.5 amps.  Perfect for the Collins 30L-1.

Another option is to externally convert the 30L-1 to full QSK operation and
use an interface like that offered by Ameritron (QSK-5), or Array Solutions'
"QSK Master."  These two devices should take care of the rig to amp
interfacing.  If you're into construction projects, see AD5X's related
construction article on his website.

Paul, W9AC


----- Original Message -----
From: "Eric Swartz WA6HHQ - Elecraft" <[hidden email]>
To: "Butch Schartau" <[hidden email]>
Cc: <[hidden email]>
Sent: Saturday, August 29, 2009 3:32 PM
Subject: Re: [Elecraft] Collins 30L-1 amp with the K3

> HiButch,
>
> Do not hook the K3 directly to the 30L-1. The K3 only switches positive
> voltages to ground on TX. Hooking up a negative voltage will not work
> and may damage the Keyout keying transistor.
>
> An external relay or a negative voltage keying transistor buffer are the
> best ways to do this.
>
> Butch Schartau wrote:

The K3 specs says

>> +200 VDC, at 5 amps, I guess the K3 does not like the minus voltage on
>> the
>> 30L-1 key line, any suggestion other than an external relay?
>>
>> Butch K0BS
>>
> ______________________________________________________________
> 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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