[Elecraft] New Output Power Issue

[Ron D'Eau Claire]

Wow. That will certainly explain the drop in RF power output. 

I would not suspect corroded pins on the KPA connectors since resistance
there will limit the current the PA can draw and actually reduce the voltage
drop. 

Are you looking at the voltage reported by the K3's display? If so, can you
check the output of the power supply to confirm that it is not drooping
under load. 

Next, I'd carefully inspect the power cable from the power supply to the K3
- especially the connectors. If your power supply has bolt-on terminals for
the power cable, be sure they are tight (I've seen Astrons shake a nut loose
through the low level vibration from the power transformer over a period of
months when they weren't tightened properly in the first place).

At the other end, is there any discoloration in the contacts in the
powerpole connecter? Are the contacts fully inserted in the housing?

Do you have anything else between the power supply and the K3 - power
distribution box or in line fuses, etc? If so, they can introduce the
resistance causing the voltage drop through a bad contact. 

73, Ron AC7AC



-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Ian Kahn - Ham
Sent: Monday, December 24, 2012 7:18 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] New Output Power Issue

Update on my low output issue:

I ran the TX Gain Calibration this morning, and everything passed with
flying colors.

I am seeing about a 4-4.5V drop across the radio when going from rx to tx.
Rx voltage sits at 13.8V, but when I transmit, voltage across the rig drops
to between 9 and 9.5V.

All tests performed while tuned into a 300W dummy load.

Before I tear into my rig and start looking for corroded tin pins on the PA
board (K3 #281, so unlikely the board was replaced/mod performed), is there
anything else I should test while my station is still all together in one
piece?

Thanks to everyone for the assistance, and Merry Christmas!

73,

--Ian

Ian Kahn, KM4IK
Roswell, GA  EM74ua
km4ik.ian at gmail.com
K3 #281, P3 #688
HRD v5.x/6.0 Test Team

On 12/23/2012 5:07 PM, Don Wilhelm wrote:
> Chuck,
>
> It could - defer decisions on that until after doing the TX Gain 
> Calibration.
>
> 73,
> Don W3FPR
>
> On 12/23/2012 5:01 PM, hawley, charles j jr wrote:
>> Could it be/affect a 40% difference?
>>
>> Chuck, KE9UW
>> Lionel Trains, TCA, LCCA, LRRC
>> aka Jack, BMW Motorcycles BMWMOA #224
>>
>
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