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.
_______________________________________________
Elecraft mailing list
Post to: [email protected]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
