[Elecraft] KX1 2468 low(ish) power output

[Don Wilhelm]

  Ron,

It is NOT safe to operate the KX1 (or any other transmitter) without the 
heat sink - the PA transistor will become "like toast" in a matter of 
seconds.

If you need to operate the KX1 outside the enclosure, make yourself a 
temporary heat sink.  I use one of aluminum material about 2mm thick and 
about 5 cm square.  There is a hole near the corner with a countersink 
where I insert the nylon screw.  That heatsink can be positioned so it 
does not interfere with making measurements - Caution, it will be 
"alive" with the full power supply voltage, be careful that it does not 
touch anything.

As to your low power output problem, look carefully at the LPF toroids.  
Be certain they are wound with the correct number ot turns.  Builders 
often put one extra turn on toroids - remember that a straight wire 
through the center of a toroid core is one turn - a complete wrap around 
the core is 2 turns.

If you find an extra turn on L1 and L2, then check the turns of T1 for a 
similar condition.

73,
Don W3FPR

On 7/6/2011 7:01 AM, Ron Hahn (EI2JP) wrote:
> Colleagues,
>
> I've just completed building KX1 2468 and I'm a bit perplexed about the
> 20 and 40 metre transmit test.  With a 13.8v supply here's what I see:
>
> 20m    3.0w    630mA
> 40m    2.5w    430mA
>
> This is barely spec for 20m and out of spec for 40m.
>
> I referred to the troubleshooting guide, and checked the following:
>
> R4 fully clockwise
> Nylon screw inserted through the tab of Q6
> ATU not installed and jumper present
> Power output measured on my WM-2 with 50 ohm known load
> Relays seem to click when changing from 20m to 4om and vice versa
> Continuity check of T1, L3, L1, and L2 for poorly stripped/soldered leads
>
> I have not (yet) checked for a short or incorrect value in the BPF or LPF
>
> Is it safe to operate the transmitter for short periods of time with the
> PA heatsink disconnected (i.e. removed from case)?
>
> Thanks for the helping hands,
>
> Ron EI2JP
>
>