K2 ...Does High DC Current cause RF power to fold back ?

[Jimithy66]

Am in final testing of a K2 Ver.A kit and transmit output
will not go above 2 watts on an external power meter
and 50 ohm load when keyed or pressing Tune.

"Hi Cur" flashes briefly and power is limited to 2 watts
Display....E = 11.9  and I = 2.0  Keyed     (Un-keyed I=0.22) .

Any idea where to start looking ?

Thanks,

Jim / W1FMR
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[Don Wilhelm]

Jim,

Yes, the K2 limits the power in a HI CUR condition.

First your DC voltage is low.  Check the power cable and make certain
all connections are tight - I recommend #16 wire for the power cable,
but #18 should be OK.  If you are using something smaller, change it to
the heavier wire.  If your power supply is adjustable, increase the
voltage to at least 13.8 -- 14.5 volts is even better.  A 4 to 6 amp
regulated power supply will be adequate for the base K2.

Does this Hi-Cur condition occur on all bands?  Or only 40 meters?
If only 40 meters, did you wind the 40 meter Low Pass Filter inductors
as indicated in the original manual?  Or did you wind them from a more
recent manual?  Check the number of turns - yours should have 16 turns
on both L25 and L26 unless you altered the capacitors in the 40 meter
LPF to correspond to the newer configuration with 5 capacitors.

Normally a Hi Cur along with low power problem says there is a problem
with either T4 or the LPF.  T4 should be wound with the 2:3:1:1 ratio.
While it can be wound with a 2:2:1:1 ratio for better efficiency at 5
watts and below, that is for CW only, and the efficiency will be less
above 5 watts - and should never be used with the KSB2 option or the
KPA100 option installed (or any external amplifier).

When counting toriod turns, count the number of times the wire passes
through the center of the core.

73,
Don W3FPR



On 6/1/2019 2:48 PM, Jimithy66 wrote:
> Am in final testing of a K2 Ver.A kit and transmit output
> will not go above 2 watts on an external power meter
> and 50 ohm load when keyed or pressing Tune.
>
> "Hi Cur" flashes briefly and power is limited to 2 watts
> Display....E = 11.9  and I = 2.0  Keyed     (Un-keyed I=0.22) .
>
> Any idea where to start looking ?
>
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html