[Elecraft] RE: A Bad Thing Happened To My K2 - Update 1

[Joe Subich, W4TV]

> I have no measurable RF output on 40m or any meaningful RX on 40m.  
> 
> The RX/TX works on all other bands including 160m.
> 
> I get the same RX/TX results from ANT1 & ANT2 and main.
> 
> I get the same RX results on the receive ANT.

The only thing I see that is common to transmit, receive and 
the RX antenna and is only in circuit on 40 meters is the Band 
Pass Filters - particularly the toriods L1 and L2.  

If you had not said the RX Ant was also dead, I would suspect 
L25 and/or L26 in the Low Pass filter.  

If you have a separate antenna for 40 meters and are connecting 
it to the receive antenna for testing, I would also check the 
antenna (or tuner).   

> My guest had a strange look on his face and I asked what 
> happened.  There was a spark from the outside of the antenna 
> connector on the back of the K2 to the center connector of the 
> coax.

This would indicate a DC path through the secondary of the PA 
output transformer, (RF board), through the LPF and to the 
antenna connector.  With +12V on the chassis (reversed power 
supply), I can see damage to one or both of the toroids in the 
LPF, damage to relay K12 or damage to the antenna system (balun?). 

73, 

   ... Joe, W4TV 
 



> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Mark 
> Saunders, KJ7BS
> Sent: Tuesday, September 23, 2008 11:51 PM
> To: 'Elecraft Mail List'
> Subject: [Elecraft] RE: A Bad Thing Happened To My K2 - Update 1
> 
> 
> Thanks to everyone for the suggestions.  Here is some more 
> information resulting from your suggestions.
> 
> I have no measurable RF output on 40m or any meaningful RX on 40m.  
> 
> The RX/TX works on all other bands including 160m.
> 
> I get the same RX/TX results from ANT1 & ANT2 and main.
> 
> I get the same RX results on the receive ANT.
> 
> Mark, KJ7BS
> Glendale, AZ
> Editor, The SKCC Centurion
> Elecraft K2 S/N 0539
> Fists # 2972 CC 1806
> SKCC # 2240 C56 T20
> MQFD # 128
> QRP-ARCI # 12647
> AZ ScQRPions
> COGRC Emergency Communications
> 
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Mark 
> Saunders, KJ7BS
> Sent: Monday, September 22, 2008 10:04 PM
> To: Elecraft Mail List
> Subject: [Elecraft] A Bad Thing Happened To My K2
> Importance: High
> 
> This evening I had a guest ham in the shack who was curious 
> about my K2 and asked if we could hook it up.  So we did.  I 
> pointed out which 12v power strip, power cord, and antenna to 
> use.  While I was getting the proper computer interface 
> cables hooded up, my guest connected the radio to the power 
> and switched it on.  I heard a loud snap and immediately 
> looked in the direction of the K2 operating position.  My 
> guest had a strange look on his face and I asked what 
> happened.  There was a spark from the outside of the antenna 
> connector on the back of the K2 to the center connector of the coax.
> 
>  
> 
> That can't happen, right?  Wrong.
> 
>  
> 
> After shutting down the power supply and inspecting things, I 
> discovered my guest had wired the power backwards.  
> Fortunately the reverse polarity circuitry protected the 
> radio and internal battery.  The radio was operating from the 
> battery, that's why it came on.  I still can't understand 
> where the spark came from.  However, I now have virtually NO 
> receive on 40m, that's where the radio was when the spark 
> occurred.  I have transmit and receive on all other bands and 
> transmit on 40m, just no receive on 40m.
> 
>  
> 
> That spark killed something dealing with 40m receive.  It is 
> so bad I can't even hear the local oscillator around 7000 KHz 
> with the pre-amp on.  There is no CW or SSB receive.
> 
>  
> 
> Mark, KJ7BS
> Glendale, AZ
> Editor, The SKCC Centurion
> Elecraft K2 S/N 0539
> Fists # 2972 CC 1806
> SKCC # 2240 C56 T20
> 
> MQFD # 128
> QRP-ARCI # 12647
> AZ ScQRPions
> 
> COGRC Emergency Communications
> 
>  
> 
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