Re: (K3) with FL2100B amp

Posted by Joe Subich, W4TV-4 on Aug 19, 2010; 7:43pm
URL: http://elecraft.85.s1.nabble.com/K3-with-FL2100B-amp-tp5441509p5441842.html


 > The FL2100 'RY' relay control switches 12V @ 200mA only.

Use a voltmeter to check the keying line on your FL-2100
or FL-2100B.  The manuals for both of those amplifiers show
a relay keying voltage between -13V and -18V.  The relay
voltage is derived from a 13V transformer winding through
a half-wave rectifier (series diode) and 1000 uF capacitor.
the -16V (+/-) under load is used for both grid bias and
relay power.

Note, if the amplifier was ever modified to use Svetlana 572B
tubes, the half-wave rectifier may have been replaced by a
voltage doubler and the open circuit relay voltage would be
-35V!

In either case, the FL-2100/2100B will not work directly with
the K3 "Key Out" signal.

73,

    ... Joe, W4TV


On 8/19/2010 2:18 PM, Tom Boucher wrote:

> Chuck,
>
> I don't think you're right - the K3 'Key Out' is spec'd 200V @ 5A. The FL2100 'RY' relay control switches 12V @ 200mA only.
>
> 73
> Tom G3OLB
>
> AE4CW wrote:
>> However, you will need an interface to key the amp from the K3 as the amp
>> keying voltage is not compatible with the K3.  I used a simple 12V reed
>> relay powered from the K3 12V RCA jack.
>
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