[K2] SSB Failure

[W4CU]

I bought a used K2/100, at the end of last year.  (Serial 5540 -  K2 MCU
2.04P, K2 IOC 1.09, KSB2  1.08, KPA100  1.10).  I mostly use CW but do
need SSB at times.  SSB had been working fine but recently RF output  
starts out fine - folks reply to my calls - but it then fades out to
zero after about 2 minutes of use.   The same thing happens whether I'm
running 100 watts or 5.  If I turn the rig off for ten minutes or so it
will again show  full output but again fades quickly to zero.  I can
still get full output on CW even after this happens.  If anyone has any
thoughts on simple things I might check, please let me know.  Thanks -
Tom W4CU
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[Bill K9YEQ]

First place to start when trouble shooting is the power supply.  Check the
voltage as the problem begins to occur.  If the receiver works when not
transmitting it could be recovering enough to keep the radio running.  

Bill
K9YEQ


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of W4CU
Sent: Monday, March 28, 2011 8:56 AM
To: [hidden email]
Subject: [Elecraft] [K2] SSB Failure

I bought a used K2/100, at the end of last year.  (Serial 5540 -  K2 MCU
2.04P, K2 IOC 1.09, KSB2  1.08, KPA100  1.10).  I mostly use CW but do need
SSB at times.  SSB had been working fine but recently RF output starts out
fine - folks reply to my calls - but it then fades out to
zero after about 2 minutes of use.   The same thing happens whether I'm
running 100 watts or 5.  If I turn the rig off for ten minutes or so it will
again show  full output but again fades quickly to zero.  I can still get
full output on CW even after this happens.  If anyone has any thoughts on
simple things I might check, please let me know.  Thanks - Tom W4CU
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[Don Wilhelm-4]

  Tom,

My first suspicion is that the ALC is continually building as you
speak.  You should be able to confirm that by switching the LED bargraph
display to indicate ALC - if the ALC meter does decrease between voice
peaks, but slowly builds up, you should see it on the bargraph.

A bad solder connection on one of the ALC components on the KSB2 board
would cause that behavior.  Look at the lower left corner of the KSB2
schematic to identify which components are involved.

73,
Don W3FPR

On 3/28/2011 9:55 AM, W4CU wrote:

> I bought a used K2/100, at the end of last year.  (Serial 5540 -  K2 MCU
> 2.04P, K2 IOC 1.09, KSB2  1.08, KPA100  1.10).  I mostly use CW but do
> need SSB at times.  SSB had been working fine but recently RF output
> starts out fine - folks reply to my calls - but it then fades out to
> zero after about 2 minutes of use.   The same thing happens whether I'm
> running 100 watts or 5.  If I turn the rig off for ten minutes or so it
> will again show  full output but again fades quickly to zero.  I can
> still get full output on CW even after this happens.  If anyone has any
> thoughts on simple things I might check, please let me know.  Thanks -
> Tom W4CU
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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