RE: KPA100 Upgrade and KAT100 Problem

Posted by Don Wilhelm-3 on Nov 18, 2006; 10:55pm
URL: http://elecraft.85.s1.nabble.com/KPA100-Upgrade-and-KAT100-Problem-tp440984p440987.html

John,

It sounds like your KPA100 is self oscillating when on 80 meters (and
perhaps other bands too).
That fact alone will drive your KAT100 crazy.
An oscillation problem will not show up on a dummy load because the dummy
load is not frequency sensitive (an antenna and tuner will be frequency
sensitive).

Check your work on the KPA100 upgrade.  I know that if Q6 and Q7 are not
working properly, the KPA100 can turn into a big oscillator.  Check the DC
Voltages of Q6 and Q7 against the DC Voltage chart in the new KPA100 manual
(download it from the Elecraft website - the one in your older manual is not
correct after the upgrade).

Leave the KAT100 situation rest until you have the KPA100 working properly.
You might want to use only your manual tuner while testing the KPA100.

The KPA100 locking up sounds like an RF feedback problem, and if present,
that can complicate your observations.

73,
Don W3FPR

> -----Original Message-----
>
> Don -
>
> I have gone from bad to worse.  I remelted some solder joints, replaced
> the 1n5711 diodes, and re-calibrated the tuner.  It seemed to work for a
> bit, but problems returned.  But now the K2/100 also has problems.
>
> With the KAT100 I tuned the antenna to 80m.  It worked OK on QRP, but
> with the KPA100 engaged the amp shows high reflected and locks on
> transmit.
>
> I removed the KAT100 and used a manual tuner.  Tunes fine at QRP, but
> with the KPA100 on, it is like the K2/100 is on a different frequency.
> The tuner setting that was fine in QRP now has high SWR.  When I go from
> 20w to full power, the K2 locks in transmit at full power out.  I have
> to power it off to quit transmitting.
>
> This same set-up, manual tuner, and antenna have worked fine since it
> was setup weeks ago.
>
> With a dummy load on the K2/100 all works well.  Tried other cables and
> yet another tuner with no success.  The K2/100 locks up.
>

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