[Elecraft] KPA100

[Mike Harris]

Hi,

KPA100 passing its final testing.  One point of interest:

KPA100 inverted, resting on a couple of thick books, shield off.

Enter tune mode and output settles at 20W then after a short delay the
indicated and actual output starts oscillating between 20W and 16W at about
one second intervals, indicated on both the K2 display and the external
wattmeter.  Voltages around U5B track up and down with the output change as
would be expected. The same thing happens even if the power level is
subsequently raised or lowered from the 20W level with use of the power
control.

It doesn't happen with the KPA100 in bypass mode.

There could be a temperature element in this because it is more common when
the heatsink is at room temperature and after a few tune runs when the
heatsink warms up the output is more stable.

Anyone else noticed this?

Something else.  When first powering up the PA via the K2, (no high current
PSU connected) the fan ran.  To get rid of the noise I did the CAL tPA
routine and the fan switched off.  After powering down the K2 and then back
on the fan started again and the CAL tPA readout was 256.  Winding it back
down the 22C all OK but the same thing happened next time.  The CAL tPA
setting only "stuck" after powering up via the high current PSU.

Regards,

Mike VP8NO (IOTA SA-002)
GQRP 10148
K2 #1400