PA gone crazy - next episode and solution

[g3pjt]

Hi

I had another play with the K2 as the problem kept recurring. I had a look
at CAL tPA and the setting was '0C'. I have reset it to 25C to see if that
was the problem.

However I still can't see how this setting could have changed.

I guess that it was changed however when I upgraded to latest software.

I need a better checklist for such changes.

Anyway for  future notes the symptoms are that when you turn on the fan
comes on high straight away even though the sink is cold, if you then press
the key with the PA on set greater than 10 watts. The display says 'PA hot'
or Hi Rflec' and the keying is garbled. And there is no power output.
Yet for QRP it all works fine.

73

bob G3PJT


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[Jim Brown-9]

On Thu, 10 Jun 2004 10:26:55 -0000, g3pjt wrote:

>I had another play with the K2 as the problem kept recurring. I had a look
>at CAL tPA and the setting was '0C'. I have reset it to 25C to see if that
>was the problem.
>
>However I still can't see how this setting could have changed.

I have had this problem occur at least a half dozen times. I have tracked it
down to a condition where the temperature of the radio drops significantly
below room temperature. My hamshack in Chicago is in a west-facing window,
and sometimes I leave the window open a bit to cool the shack. A cold breeze
coming in that window will cool the radio enough to set off this problem
(that is, to cause the radio to go into over-temperature protection and stop
transmitting).  I've made Wayne aware that this is what sets off this
problem. And yes, resetting CAL tPA solves it.

Jim Brown  K9YC

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[wayne burdick]

I haven't been able to duplicate this yet, but given the recent input,
I'll have another crack at it, this time using my refrigerator. I'll
post an update when I find the solution.

73,
Wayne
N6KR

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[Douglas Westover]

This happens to my KPA100 from time to time.
Upon investigation the tpa value is always 255
and the problem is solved by resetting it to
room temperature. I haven't been able to
correlate this to any actual temperature changes
as the temperature in my shack probably doesn't
vary more than (+, -) 7 or 8 degs F.

What I DO notice is that it usually occurs after a
tune cycle that requires the KAT100 to do more
switching than normal. My guess is that it has to
do with a high SWR condition (hence the Hi Refl
message also) that somehow causes all of the
bits in the tpa register to get set. This assumes
an 8 bit value for tpa.

My KPA/KAT 100s are in a separate EC2 enclosure.

73,
Doug
W6JD
K2 #1626

----- Original Message -----
From: "wayne burdick" <[hidden email]>
To: "Jim Brown" <[hidden email]>
Cc: <[hidden email]>
Sent: Thursday, June 10, 2004 9:25 AM
Subject: [Elecraft] PA temperature issue (CAL tPA)

> I haven't been able to duplicate this yet, but given the recent input,
> I'll have another crack at it, this time using my refrigerator. I'll
> post an update when I find the solution.
>
> 73,
> Wayne
> N6KR
>
> _______________________________________________
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> Post to: [hidden email]
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> Subscriber Info (Addr. Change, Unsub etc):

http://mailman.qth.net/subscribers.htm
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[Kurt Cramer]

I have seen the problem, but only after a high SWR tune. I have a K2/100
and an MFJ-986 tuner. RF grounds are non-existing in this shack.

73, Kurt                        

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