[Elecraft] External AMP

[K9MA]

The unmodified SB-230 used -130 V to switch the relay. Clearly a buffer 
relay or interface circuit is required to use that amplifier with the 
K3, or any "modern" transceiver.

Scott K9MA



On 12/1/2018 16:54, Don Wilhelm wrote:
> Ray,
>
> That relay power is normally provided by the amplifier - you do not 
> need any voltage from the transceiver unless there is some strange and 
> unusual circuit involved.
>
> Measure the voltage at the "PTT" or "KEYIN" jack of the amplifier.  Is 
> it AC or is it DC?  If AC, it will not work with the K3S which needs 
> for the voltage to be both positive and DC.
>
> If it is DC, what is the polarity?  It must be a positive voltage.
>
> Many older tube amplifier designs depended on hard relay contacts for 
> keying that cold work with AC or DC and did not care about polarity.
> In today's solid state world, one must care about such things.
>
> On 11/30/2018 10:02 AM, Raymond wrote:
>> I am using my ancient Heathkit SB 230 (original tube) with my K3s. Is 
>> there a way to get 12 volts out of acc connector to power relay?  
>> Using K3 external plug for P3 power.
>> Ray
>> W8LYJ
>>
>> Sent from my iPhone
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-- 
Scott  K9MA

k9ma at sdellington.us