[Elecraft] Collins 30L-1 amp with the K3

[Don Wilhelm]

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
>   
>