After some more trouble shooting with Gary from Elecraft, he decided to send
me a new U4. After installing it, all tests and alignment for step 2 went
off without any issues at all.
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I'm glad to see you solved the problem.
Exchanges like this one between Jeremy, Don and Gary are one of
the reasons I read everything on this list, and not just the
items for the equipment I own.
Cheers - Bill, AE6JV
On 2/13/13 at 4:50 AM, jjones9...@gmail.com (JeremyJones) wrote:
After
So Gary from Elecraft gave me some things to check today. Heres where I am
at for the moment.
T5 is back to 15 turns of red. This brings the frequency close to spec @
TP1.
Pulled C72 and measured its value at 273pF.
U6 has 4V @ pin5 and pin1 goes from 7.5 to 0V when doing the PLL range test.
T5
So Cal PLL is still not working.
The 5V from U4 pin13 makes it all the way to U6 pin 6, but is blocked by C94
on the other branch.
Still only 0.020V at R30.
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Sent from
So this morning I started rechecking everything. I've found that the 5V on
U4 pin 5 is intermittent. Not in a way that would indicate a loose or poor
connection, but either that it is there, or it isn't (mostly isn't) when
powering up the unit. U7 always has the 5V on pin2. I checked the
Jeremy,
U7 pin 2 and U4 pin 5 are both the SDO signal which comes from the
microprocessor over on the control board.
If you have 300k resistance between those two points there is a break
between them.
I don't know why you mention U7 pin 5 (unless it was a typo) because
that pin is connected
Looking over the board I did find that I had U8 C45 connected to pin7 instead
of pin6. That has been corrected.
U6 pin 24 to U4 pin5 is less than 1 ohm, however U6 pin24 to U7 pin2 is 300k
ohm. I don't see any damage on the board.
I also noticed going back to the beginning for the resistance
Jeremy,
Do I recall correctly that you had a good PLL range? If so, I have
trouble believing there would be 300k resistance from CB U6 pin 24 to RF
U7 pin 2 while you have zero ohms to U4 pin 5. Are you certain you
counted the pins correctly? Pin 1 has a circular solder pad and the
rest
Rechecked the resistance, and indeed there is 300k from U6 pin 24 to U7 pin2.
Looking at the schematic in the manual, it shows U6 pin24 connected to U7
pin5 and U8 pin11. At this point I do have less than 1 ohm.
The schematic shows U6 pin23 connected to U7 pin2 which is reading less than
1 ohm.
Jeremy,
I am sorry, I had the wrong IC, RF board U5 pin 2 should be connected
to Control Board U6 pin 24. Yes, it also connects to Control Board U7
pin 5 and Control Board U8 pin 11, as well as RF board U4 pin 5.
73,
Don W3FPR
On 2/3/2013 3:45 PM, JeremyJones wrote:
Rechecked the
No problem Don, you've been a huge help.
So I went back to the beginning and did all resistance checks in the manual
up to this point and everything is good.
PLL range test @ 7100.00khz gives me 12099.13 high and 12086.33 low.
VCO @ 4000.10 gives me 7840.33
I do still have some bad voltages
So I really thing that U4 is faulty. It's putting out 5.029V on pin13 when
that should only be 4V. All the components surrounding it seem to have the
correct voltages according to the manual. I think I'll replace that and see
how things look after.
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Jeremy,
5.029 volts at U4 pin 13 means that the PLL synthesizer IC is working.
Remember that the manual voltages are for a properly working K2 that has
the PLL IC in lock with the VFO frequency. Your voltage only indicates
an out of lock condition.
What is the R30 voltage now with that
I'm in the process of building a K2 and am having trouble at the Alignment
and Test part 2. I've gone through at ton of previous posts here an have
been talking with Gary at Elecraft but no luck so far. The main issues are
C22 only has adjustment less than 1khz (12085-12086) @ TP3, and R30 which
Jeremy,
I have read your exchanges with Gary,
First, don't bother with the C22 setting - just set it to the midpoint
(slot parallel with the long edge of the board) and leave it there until
you have the rest of the K2 receiver working on all bands, and then go
to my website www.w3fpr.com and
Hi Don,
I set C22 to midway.
PLL @ TP3 is 12099.12 - 12086.32.
T5 is a yellow core, wound with 15 turns red and 4 green. I had to bring it
down to 15 turns as recommended by Gary to get 8253.86khz @ TP1 when tuned
to 4000.10 for the VCO test. It was around 7694.39 with 16 turns.
L30 is the
Jeremy,
Unless you have a typo, the 40 meter VFO frequency is too high while all
the rest of the bands is too low.
Make certain that the value of C71 is 82 pF and re-flow its soldering.
Set the K2 to 7000 kHz and re-measure the VFO frequency - probe in TP1
Next (while you are still in CAL
Jeremy,
I did some playing with numbers in the VFO resonant circuit, and I am
coming to the conclusion that L30 and T5 are not connected together. If
my speculation is correct, you will find a break in the PC board or
something not soldered.
With the K2 upside-down, look at the bottom of
Don,
Checked D19 is n in the secondary menu. L30 does change frequency.
Soldering iron is set to 775F. I'm using one of those illuminated workbench
magnifying lamps to examine my work. Even still I reflowed the solder on
all joints to be sure. U6 circuit components are the correct values and
Jeremy,
OK, let's back up to U4 and U6 for a bit. Set the K2 to 7100 kHz and
tell me the voltages at U4 pin 13. U6 pin 6 and U6 pin 7.
You can remove the bridge between L30 and T5.
Also lift one lead of the red winding on T5 and check the resistance
across L30. In the row of 3 pins,
U4 pin13 = 5.029V
U6 pin6 = 5.026V
U6 pin7 = 0.020V
L30 with 1 red lead removed = 0.5ohm
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Jeremy,
That 5 volts at U4 pin 13 is higher than normal, and is the reason you
do not have any control over the frequency of the VFO.
Make certain the path from the VFO output through C62 to U4 pin 4 is
intact with good soldering all the way. Check the value of C62 (0.01
uF marked 103).
C62 is correct, and the path is intact. Reflowed the solder on all
connections just to be sure.
U4 readings are as follows
Pin1 = 0.111
Pin2 = 0.339
Pin3 = 0.006
Pin4 = 2.363
Pin5 = 4.99
Pin6 = 4.99
Pin7 = 4.99
Pin8 = 4.99
Pin9 = 0.001
Pin10 = 0.001
Pin11 = 0.000
Pin12 = 0.000
Pin13 = 5.029
So I started tracing back and checking joints and reflowing solder. I now
have 0.760 @ pin8, 0.000 @ pin 13, and 0.00 @ pin 15.
R30 is now showing 8.04V, but 40M is reading in the 13000khz range, with L30
able to adjust frequency but not voltage.
I'm thinking I may need to add back in the turn
Jeremy,
The DC voltages at U4 pins 1 and 2 are suspicious. The voltage at pin 5
is from the MCU digital outputs, so I would not be to concerned about it
just yet. However, compare the voltage at U4 pin 5 with the voltage at
U7 pin 2 - that is the same signal, and the voltages should be the
Jeremy,
You are making progress.
That is a good indication that you have resolved the problem.
Yes, add back turn 16 of T5 and things should come into normal.
Hint - you may still have to spread/compress the T5 windings, but as an
aide to know which is to be done, tune down from 4000 kHz to
Thanks Don,
I'll rewind T5 and see where that gets me.
U4 pins 1 and 2 are still low (no change), and U7 pin2 and U4 pin5 are
equal. Do you still suspect there may be an issue with U4?
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Jeremy,
Since you now have 8 volts at the left end of R30, I would wait and see
if you can get all the band end R30 voltages into spec with adjustment
of L30 and the turns spacing of T5. If so, I would ignore the DC
voltages at U4 pins 1 and 2. Those voltages are partially a result of
just
Rewound T5 and now I seem to be back at square 1.
U4 pin13 is high again @5.029V when tuned to 7100khz.
R30 is back to 0.02V
40M is at 11351.25
L30 still changes frequency.
The VCO test at 4000.10 results in 7794.5 @ TP1.
U7 pin2 and U4 pin5 are both 4.99V.
I think I'll call it quits for tonight
Jeremy,
While you sleep on it, think back to whatever caused he R30 voltage to
go to high ( 8+ volts). That is the key to whatever is happening.
I am also calling i quits for the night - have a good rest.
73,
Don W3FPR
On 2/2/2013 11:06 PM, JeremyJones wrote:
Rewound T5 and now I seem to
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