1. Elecraft-K3@groups.io

Re: K3 reduced or no TX output on low and high bands

mikerodgerske5gbc
 

If they are cold they are dead.  It's usually 1.  You do the test in ssb with power at zero.  I can dig up the information. 
The fet's are field serviceable or if elecraft has extra complete boards.  

Been there done that. 
Note: I believe my problem was on 15 meters so be careful there?

73
Mike R

7!
Absolutely Awesome 

On Apr 16, 2020, at 10:26 AM, Ray Maxfield <wa6vab@...> wrote:

I had a similar problem.

Locate the 3 Driver Fets that use the bottom cover as a Heat Sink (see Assembly Manual).

I would do this test on 80 Meters. In the SSB or AM mode Key the PTT or TX and FEEL

The bottom cover to see if the Driver  FETS Gets HOT.   If Hot they are most likely shorted.

I think I found this test on U-TUBE.  If none of the Driver Fets gets Hot, then I would look

At the Output FETS.  If you are Comfortable Working on the Radio, you can take the bottom

Cover off and remove the FETs from the board and test them with a Multi-meter.

Hope that helps…….. Ray WA6VAB.         

 

From: Jarmo Blomster
Sent: Thursday, April 16, 2020 6:59 AM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] K3 reduced or no TX output on low and high bands

 

I sent this to K3 support, while waiting their answer I ask here also.

Serial is 0691.

 

Last week I noticed that my K3 has no TX output on 6m band.
I run Transmitter gain adjustment procedure on all bands.
I noticed that 160m and 10-6m has problems and can not finish properly the adjustment procedure.
Here are my results using a dummy load:

 

Transmitter Gain adjustment
Measures RX: 14.9V, 1.19A, PA 24C, FP 20C
Band, Reaching Power, SWR,   Voltage, Current, Error
160m,             2W, 1.2-1, 14.7V,    2.78A, ERR TXG
 80m,             5W, 1.0-1, 14.6V,    3.27A
 60m,             5W, 1.0-1, 14.6V,    3.33A
 40m,             5W, 1.1-1, 14.6V,    3.30A
 30m,             5W, 1.0-1, 14.6V,    3.38A
 20m,             5W, 1.0-1, 14.6V,    3.19A
 17m,             5W, 1.0-1, 14.6V,    3.19A
 15m,             5W, 1.0-1, 14.6V,    3.25A
 12m,             5W, 1.0-1, 14.6V,    3.24A
 10m,             5W, 1.0-1, 14.6V,    3.35A, ERR TXG

  6m,           0.1W, --,    14.8V,    2.19A.

For the measurements I replaced the KAT with the antenna interface card, so the problem is not in KAT.
I guess that possible components that can cause such problems are LPA and maybe the SWR Bridge.
What components in the LPA or in SWR bridge can cause such?
Has anybody had similar problems?

73 de Jarmo, OH8KVA

 
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