I am troubleshooting a K1 that has no output.
The guide says to check Q5 and U8 voltages but I do not find them listed anywhere.
The DC voltages table lists U8 pin numbers but no voltages. I see nothing for Q5.
If anyone knows what they are or where they are listed I would appreciate a reply.
The receiver works ok and all the voltage and resistance measurements listed in the
assembly part of the manual and those of U9 Q8 and Q7 are all good.
I do not know where those DC voltages are listed. For as long as the K1
has been out, I don't understand why that omission had not been spotted
However, back to your problem - the quickest path to resolution is to go
first to page 5 of the manual troubleshooting appendix and build an RF
Probe (if you have a 'scope with a 10X probe, it can be used instead).
The RF Probe does not have to be pretty, or shielded or anything like
that. If necessary, punch the leads of the components through a piece
of cardboard to provide support, just connect the leads as indicated.
OK, RF Probe in hand, or 'scope (if using a 'scope, the Expected
voltages will be shown in peak to peak which are 2.8 times the RMS
voltages listed), go to the Transmit Signal Tracing section. What you
are looking for is the first stage where the RF voltages are
significantly *lower* than the expected value. If the voltages are
higher, that is OK, and is normal for a K1 that is not developing any RF
Once you have identified the failing stage (the one where the output is
lower than expected, stop and let us know - we can help with detailed
analysis of that stage.
With an RF probe, I did not get any reading from the first test point, PRE (premix) nor the latter test points in the manual.
I do get a good reading on pin 4 of P1 on the filter board which should be the premix oscillator signal.
I do get the correct voltages on U7 on the RF board when checked per the voltage table instructions.
I do not get a reading on pin 6 of P1 on the filter board which should be the premix signal output.
Any suggestions would be much appreciated.
I will double check some things.
Since the DC voltages for U7 are correct, and the crystal is
oscillating, you most likely have a problem on the band board - either a
soldering problem or if you have the 4 band board, a problem with the
lead tinning or positioning on T1 and/or T2.
If you do have the 4 band board, did you position the trimmer caps
initially with the slots parallel to the long side of the board? If
not, do that and check again.
I remember you saying you had taken out the KAT1 for these tests. Did
you re-install the RF-DET jumper on J2 after you did that? That is an
error I have made myself, and I'm afraid it is my only suggestion.
It is the two band board with 40 and 20 meters.
I have looked over the filter board several times and re-soldered some joints just to be sure.
I will look over it again.
I used the pre-wound coils but will look them over again and make double sure the right one is in the right place.
The problem will be found either in the bandpass filter on the left end
of the 2 band board, or in the connections between the filter board and
U7 Check the path between U7 pin 4 and the filter board P1 pin 2 and
also between U7 pin 5 and filter board P1 pin 1 - both should have close
to zero ohms resistance.
If that is not the problem, check the capacitor values for C1 through
C10 on the board against the band components chart.
You might check for continuity between the junction of C4 and C5 when
the band is set to Band1 and between the junction of C9 and C10 when set
for Band2 - the relays are latching, so you can set the band and then
remove the filter board to check for continuity.
Do you have the same problem on both bands? If so, it is probably a
connection problem. On only one band, I would suspect a wrong component.
I got it working and finished the K1 this evening. Thanks for all the assistance and suggestions.
I am not certain where the problem was but I re-soldered and touched up a few solder joints on the filter board. I think it may have been C10 as the coating on the cap was down into the via a little ways. After touching it and some other joints, I re-peaked the filters in receive and found that the 2nd premix filter of each band peaked in a different place. In transmit it came alive.
Thanks again, Mike K7MH.