Posted by
John Wiener on
May 30, 2006; 4:04am
URL: http://elecraft.85.s1.nabble.com/K2-troubleshooting-tp390323.html
Hi everyone!
I am diligently trying to solve transmitter probs on a "nearly"
finished K2.
I would like to list here the aberrant readings so that someone much
brighter than I might see the source of the problem.
If this is an inappropriate use of the group, please let me know and
I will stop immediately.
On Alignment III, I could not reach 2.0 watts by adjusting L1 and
L2. I get a transient Hi Current reading at beginning of keydown.
The current drawn was 3.5 amps (the current limit) on transmit.
(About .24 on receive)
In the troubleshooting section, I checked ALL components in PA,
Driver, Pre-Driver, PA Bias and RF Output Detector.
I could find no solder bridges and all parts appear to be correct.
I checked the windings of T1 -T4 and their solder connections...seem
to be OK.
R50 was not open.
Now I know the signal tracing section suggests I do the receiver
signal trace first, since several circuits are shared. I do not have
a signal generator, however. I just ordered the XG-2 but won't have
it for a bit. So I did the signal tracing for the transmitter.
Signal tracing for transmitter (p. 12 of troubleshooting):
I am using a Radio Shack 25 Amp switching supply reading 13.9 volts
that goes to 13.6 on receive. Transmit V=12.9 A=2.5
D6 anode is 7.9VDC (correct) and D7 is 0.2VDC. Power output is
0.3W. I hear a normal cw tone on a nearby receiver at the proper freq.
VPWR is 1.2VDC (correct)
Now, Here are the aberrant values:
Band-Pass Filter Output: 0.12 (Expected is .03)
T-R Switch #1 Output: .141 (Expected is .029)
Driver Input: 0.16 (Expected .026)
RF Detector Input: 0.7 (Expected is 2.0)
Q7 and Q8: both have been replaced once already
Transistor test Pos. Lead on Base: E and C both read about .55
(volts, I guess..."k" is listed in the manual)
Neg. Lead on Base: "OL" on C, .55 on E(expected is 1.3)
That's where I am at the moment.
If someone can explain what the settings should be for DC Voltage
tables during TRANSMIT, I would really appreciate it.
In the manual (p14) It says no antenna...this doesn't sound right for
transmit. What did I miss? Then, I can tackle the DC readings.
ANY IDEAS?
John
AB8WH
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