Don -
I am Jim, KL7CC, helping Micah with his K1.
Further testing indicates the following: With PO set for 3.0 watts
(requested) we get approx 18V PP RF at the collector of Q6, and6V PP at
the base of Q7. NO volts RF at the collector of Q7, but the DC voltage
reads about 12.8 DC. Have not tried to peak all stages, but seems to me
that the problem is likely a toasted Q7. Watcha think?
- Jim, KL7CC
On 3/4/2013 4:47 AM, Don Wilhelm wrote:
Martin and Micah,
The information Gary gave you is exactly correct.
I would add three additional comments:
1) The oscilloscope should have a 10X probe for reliable readings
(otherwise use an RF Probe)
2) If you have a 4 band board, start with the trimmer slots parallel
with the long edge of the board - the final settings will not be more
than 20 degrees from that position. You must align 15 meters (or 17
meters) before 20 meters, and 30 meters before 40 meters (the band
order is not important for the 2 band board)
3) After peaking the Pre-Mixer bandpass at P1 pin 6, go on to peak the
TX Buffer output, and then with the probe still on the TX Buffer
output, go back and touch up the Pre-Mix again - the 'scope probe may
load the premix filter output a bit and must be tweaked again without
the probe on P1 pin 6.
Observe the sequence of alignment, it must be done in order. Let us
know where the expected RF voltages cannot be reached.
73,
Don W3FPR
On 3/4/2013 1:49 AM, Foreman wrote:
My son and I have been building a 20m & 15m K1 over the past year.
Great kit! It is assembled and we are trying to finish aligning the
radio. however, it will not transmit. We have tried signal tracing it
and cannot get a reading on any of the test points. Receiver works
fine. We did extensive multimeter testing and found that IC U8,
SA602AN, was out of tolerance. We replaced it but the transmitter is
still inop. A very kind Elmer will assist us with test equipment but
wanted to gather opinions from the reflector participants on how to
proceed. Just to bring all the information together here in one
place, the great folks at Elecraft shared the following recommendations:
Filter Board RF voltages using a scope at these filter board
connector pins:
P1-4 Premix oscillator signal 200-500mVpp
P1-6 Premix signal output signal 200-500mVpp (must be peaked with the
bandpass trimmers)
P2-1 TX Buffer output 1-3Vpp
P2-8 Filter board TX output to Driver 1-3Vpp
P3-1 PA output up to 40-55Vpp
P3-8 Output from lowpass filter 40-55Vpp
Vpp = RF volts peak to peak.
mVpp = RF millivolts peak to peak.
An RF probe will show the rms RF voltage levels, or about 35% of
these pk-pk values. Appendix E, or any ARRL Handbook shows how to
build an RF probe. We also sell an RF probe kit for $10. Use an
oscilloscope if you can get access to one.
Test the rig on all bands too. The filter board is difficult to align
the first time, so be patient when aligning it, and try to peak it on
signals in receive, or in transmit with an RF probe or scope at the
indicated places shown above.
Thanks.
Martin, KL3ID
Micah, KL3IE
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