dead K2

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dead K2

Mike Baird
My K2 #5767 suddenly has quit working.  Upon power up today,  the freq. readout is OK, but none of the buttons work and the tuning dial doesn't change freq.  No error messages are seen at powerup.  

Anyone have any ideas??

--Mike, W0RSR
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Re: dead K2

Don Wilhelm-4
Mike,

The symptom of not being able to do anything from the front panel is
usually an indication that it is attempting to transmit as soon as power
is applied.  The simple thing that can cause a transmit condition is a
closed key (or PTT).  Remove anything from the micophone jack, remove
anything from the key jack and the AUX I/O if you have one.  Connect a
dummy load 'just in case' my transmit assumption is correct.
If you have the KPA100, it is preferable to power only the base K2, but
if you have only the 12 volt cable for the KPA100, go ahead and use it.

After that bit of setup, power the K2 on - does it work?  If so, one of
the external cables was putting it into transmit, your task is to find
which one and correct it.
If you still have the same problem, remove the top cover (whether that
be the KPA100 or the QRP cover.  You will be making a couple checks with
your DMM.
Power on and check the voltage at the anode of both D6 and D7 (located
halfway back about 1 inch from the left side panel).  During receive,
you should find the anode of D6 near 8 volts and the anode of D7 near
zero - during transmit, the anode of D6 should go to zero and the anode
of D7 will be near 8 volts.  If both of them are near 8 volts when you
power on, power off quickly and tell us about it.
In any case tell us what you found in the above steps before proceeding
further (or making any assumptions).  An orderly progression of tests
will lead you to the failure point.

73,
Don W3FPR

worsr wrote:
> My K2 #5767 suddenly has quit working.  Upon power up today,  the freq. readout is OK, but none of the buttons work and the tuning dial doesn't change freq.  No error messages are seen at powerup.  
>
> Anyone have any ideas??
>
>  
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Re: dead K2

Geoffrey Mackenzie-Kennedy
In reply to this post by Mike Baird
Mike,

My K2/100 #3255 behaved in exactly the same way some years ago, actually on
two occasions about a year apart. The problem was caused by dirt or
corrosion on the contacts of the socket of the MCU U6 on the Control board.
Pulling and reseating the U6 IC cured the problem on each occasion.

After the second episode I changed U6's socket to a turned pin (machined)
type of socket, and the problem has not reared its ugly head since. The type
of socket supplied with the K2 kit is often a cause of "problems".

73,
Geoff
GM4ESD



From: "worsr"
Sent: Friday, May 07, 2010 9:47 PM



> My K2 #5767 suddenly has quit working.  Upon power up today,  the freq.
> readout is OK, but none of the buttons work and the tuning dial doesn't
> change freq.  No error messages are seen at powerup.
>
> Anyone have any ideas??
>
> --Mike, W0RSR


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