[Elecraft] K1 transmitter problem...any help appreciated.

[Don Wilhelm]

Ron,

Since you have apparently exhausted most of the things that seem 
logical, perhaps it is time to look at some of the things that border on 
the 'strange and unusual'.   Suggestions follow:

1) check for a poor connection at J7.  That is best done by comparing 
the signal level on both sides of a connector pin (with a filter board 
plugged in).  Check both at pin 1 and pin 8.
2) Check the signal path through the signal path through the BPF itself 
to see where it is getting lost.
3) With a frequency counter, check the frequencies at the premixer 
output (PRE), the transmit LO (OSC), the mixer output (MIX), and buffer 
output (BUF).  There is the thought that perhaps the transmit LO could 
be way off, and the resulting frequency that you are feeding to the BPF 
is not correct.  This condition would not show up until you try to put 
the signal through the bandpass filter - and it would produce exactly 
the conditions you report.

73,
Don W3FPR
 
Ron wrote:
> Hi Guys,
>             As a last resort I am appealing to the "Elecraft 
> collective" to see if I can get help with this problem.
> I have a K1 that has been going great for years , but during a band 
> filter change it was fired up without the ATU replaced and it fried 
> the output transistor and D19.(also damaged T4 which has been 
> re-wound....and double checked since)
> I replaced both the output transistor and D19 and it "sort of " went 
> for a while then decided to die on transmit completely.
> I replaced the driver.....no change... Then I started looking with my 
> very limited quality "scope". I appear to be getting drive through the 
> Transmit mixer OK, and the buffer stage appears to giving me a 10x 
> increase in drive level. The signal looks OK until I get to point 
> "TR1" at the junctions of D5 and D14 where it goes into the BPF. There 
> is not much drive appearing at point "TR2" ....certainly not enough to 
> get the driver excited enough to work
> This problem is common to each band on two different 2 x Band boards, 
> so I have to presume they are OK.
>