Hi Dave,
Don and I have had several exchanges off list, so let me bring you up to
speed. In addition to the low VFO frequencies, I had noticed some
instability in the frequencies as displayed. Don suggested that I insert a
10-15pf cap between the source of the Q19 FET and ground. I did that late
Hi John,
I just got back in town and I know I'm late into this. I see Don is
stepping you through some things as well. Here are a couple of things I was
thinking:
Since you have a VFO output although low in frequency, I think because the
voltage at pin 7 of U6 is so high it is driving the
Hi Don,
No problem on the delay. OK, after removing 1 turn from T5, the freq. at
TP1 (at 4000) is now 8535.14, so it did come up from the previous value,
but clearly not enough. I have 4.19 V on pin 5 of U6 and I have 4.21 V on
pin 13 of U4.
I wasn't sure of your schedule so I also put in a
John,
Where did the TP1 frequency go after you removed a turn?
It is possible that the VFO frequency is not getting back to U4 pin 4 --
the signal goes from U3 pin 6 thru C62 and then to U4.
Did we verify that U6 pin 5 is near 4 volts? What is the voltage at U4
pin 13?
Sorry to go over
Don,
Finally got back to the K2 this afternoon. I have confirmed that T5 is on
the yellow core, with 16 turns through the center on the red and 4 turns on
the green. I mentioned earlier that I got all the toroids from the Toroid
Guy, so I felt confident that it was correctly wound. I checked all
et<mailto:Elecraft@mailman.qth.net>
Subject: Re: [Elecraft] K2 VCO Alignment Issue
John,
Both frequencies are too low.
You have either too much capacitance or too much inductance in the VFO.
Count the number of times the red wire goes through the center of the T5
core - it should be 16.
Check relays K13
John,
Both frequencies are too low.
You have either too much capacitance or too much inductance in the VFO.
Count the number of times the red wire goes through the center of the T5
core - it should be 16.
Check relays K13, K14 and K15 for solder bridges.
Make sure the core of T5 is yellow.
Hi Don,
Thanks for the quick response. I did check C72 again. It is a 271 value. I
then spread the red turns on T5 as far as I could. I'd say they cover about
90+% of the toroid. I put the L30 slug at mid-point of travel and measured
voltage at R30 and it is still right at 8.37 V. While there I
John,
That high voltage is trying to reduce the capacity of the varactors.
Which means there is either too much capacity or too much inductance in
the circuit.
Check the value of C72 first - it should be marked "271". Then set the
L30 slug to about mid-position and spread the red turns of
Working on my 2nd K2 (S/N 7869) and have run into a problem with the VCO
alignment. I'm getting a constant 8.37 V at R30 at 4.000 MHz.. I cannot
change it with the full range of L30. Correct type inductor is installed at
L30. Dropping the VFO down to 3.500 doesn't change it either. I have gone
Mark,
See my prior email.
73,
Don W3FPR
On 4/21/2019 1:43 PM, Mark Yergin wrote:
I'm getting 0.02 V at R30, not 6V. Turns on T5 correct and wound per
image. Reflowed the four solder joints and verified continuity between 1
and 2, 3 and 4. C72 is correct value (label 271) and reflowed. L30
U6 Pin 5 = 4.1v
PLL ref Osc range at TP3 = 12098.83 to 12084.95
VFO at TP1:
@4000kHz = 8077.0
@7100kHz = 11288.5
Mark
On Sun, Apr 21, 2019 at 6:02 PM Don Wilhelm wrote:
> Mark,
>
> First check the DC voltage on U6 pin 5. It should be near 4 volts - if
> not, you have a problem on the
Mark,
First check the DC voltage on U6 pin 5. It should be near 4 volts - if
not, you have a problem on the thermistor board, likely a solder bridge.
Then recheck the PLL reference oscillator range at TP3 using CAL FCTR.
Tell me the high and low frequencies.
Then check the VFO frequency
I'm getting 0.02 V at R30, not 6V. Turns on T5 correct and wound per
image. Reflowed the four solder joints and verified continuity between 1
and 2, 3 and 4. C72 is correct value (label 271) and reflowed. L30 is the
correct value (large slot), and reflowed. D21-26 confirmed as correct
values.
do it!
73, Jim KO5V
"Message: 3
Date: Tue, 22 Jan 2019 21:57:09 -0500
From: K2bew
To: donw...@embarqmail.com
Cc: Elecraft Mail List
Subject: Re: [Elecraft] K2 VCO Alignment T5 L30
Message-ID:
Content-Type: text/plain; charset="UTF-8"
Don Et Al,
So, It is with some embarra
Tom,
welcome to the club. I think anyone who has put together a K2 has such
stories. In my case I had installed U4 backwards and did not notice it
as the chip has a very pronounced 'dimple' on one end which (for some
reason) made me overlook the notch on the other end. I spent a week
Don Et Al,
So, It is with some embarrassment, and much relief, that I can report it
was operator error and my BFO is now working perfectly.
I got home from work and was getting ready to do some continuity checks to
all the circuits surrounding and including U11, but decided I better check
all the
Tom,
Good work on the VFO.
Before you replace U11, measure the resistance from the wire on the
carrier board to the lead of the SMD IC. Do that for all pins. The PC
traces on the carrier board are not thru-plated holes and sometimes
become damaged with soldering.
73,
Don W3FPR
On
-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of K2bew
Sent: Saturday, January 19, 2019 5:35 PM
To: donw...@embarqmail.com
Cc: Elecraft Mail List
Subject: Re: [Elecraft] K2 VCO Alignment T5 L30
Don et al,
I tried a 15pf cap
Don et al,
I tried a 15pf cap ( what I had on hand) at the source of Q19 to ground and
I got .025v on R30 that did not change with the adjustment of L30,
essentially no voltage.
So, I took it off and it went back to 4.5 volts. So, then I tried Vicenç,
EA3ADV's suggestion and I put 17 turns on the
Thanks a lot Don and Ed,
I will be working on it over the weekend and will report back.
73, Tom
On Fri, Jan 18, 2019, 10:33 AM Don Wilhelm Tom,
>
> Normally I would say to spread or compress the turns on T5, but Elecraft
> encountered a batch of J310 FETs that do not work very well at Q19 -
Tom,
Normally I would say to spread or compress the turns on T5, but Elecraft
encountered a batch of J310 FETs that do not work very well at Q19 - the
PLL reference oscillator. These troublesome FETs have now been purged
from the Elecraft stock, that the problem should go away going forward.
Don et al,
Since I know Don monitors the reflector as well as the support emails,
rather than email Don directly I thought I would ask the question on here
because I know I always find it helpful to read other peoples questions on
here and Don's answer.
Building the K2 I am at the VCO Alignment
elecraft@mailman.qth.net
Envoyé le : Samedi 28 septembre 2013 22h16
Objet : [Elecraft] k2 vco alignment
K2 #7449 VCO alignment difficulty.
Cannot get 4.0 MHz R30 voltage to change at all - it measures 7.97V. Have
confirmed all the cap values, varicap diodes are correct parts, T5 wound
K2 #7449 VCO alignment difficulty.
Cannot get 4.0 MHz R30 voltage to change at all - it measures 7.97V. Have
confirmed all the cap values, varicap diodes are correct parts, T5 wound
and wired correctly.
Have scoped the area comparing to a second operational K2 the wave forms
look and behave
Rob,
There is either too much inductance or too much capacity in the VFO
circuit - the high voltage means that the K2 is trying to reduce the
capacity to bring things into line.
Count the turns on T5 very carefully. Each wire through the center
counts as one turn - a full wrap around the
Don,
Thank you, with this it only took me 3 minutes to fix it with this info.
The coverage on T5 was the critical factor here.
The good news is that I've spent the last 4 hours confirming that
EVERYTHING else around the VCO is correct!
73, Thanks again!
kc2vmp
On Sat, Sep 28, 2013 at 5:11
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.
--
View this message in context:
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.
--
View this message in context:
http://elecraft.365791.n2.nabble.com/K2-VCO-Alignment-only-0-02V-R30-tp7569523p7569616.html
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.
--
View this message in context:
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
--
View this message in context:
http://elecraft.365791.n2.nabble.com/K2-VCO-Alignment-only-0-02V-R30-tp7569523p7569545.html
Sent from the Elecraft mailing list archive at Nabble.com.
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?
--
View this message in context:
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
I am up to page 64 of the assembly instructions for my K2 serial 7059. When
performing the VCO Alignment, I started off with a reading of 8.2 volts. When
adjusting L30 I got no changes at all, although the directions call for
adjusting the slug until 6 volts is obtained.
Any help would be
On 1/21/2011 1:07 PM, Paul Agoglia wrote:
I am up to page 64 of the assembly instructions for my K2 serial 7059. When
performing the VCO Alignment, I started off with a reading of 8.2 volts.
When adjusting L30 I got no changes at all, although the directions call for
adjusting the slug
Paul,
The first thing to check is the DC voltage at RF Board U6 pin 5 - if it
is not close to 4 volts, then you need to check the thermistor board for
solder bridges.
If the above checks OK, then try tuning downward fom 4000 kHz and see if
the voltage drops.
If it does, recount the red
I finally got my k2 #05233 completed and started the alignment process. I ran
into some issues and decided to go back and re-check the tests for phases I and
II. The tests during their construction were all ok and on the money. This time
when I got to the VCO alignment stage the following
Hi
I've worked my way through assembling my k2 and I've reached a problem:
Everything seems fine until the 4000 kHz, R30 - 6V alignment of L30. I
can only reach 5.65V. I have verified D23-26 are the right part, oriented
correctly. I have verified D21-22 are the right part and oriented
Robert,
Spread or squeeze the turns of T5 and see if the voltage increases by
that means - overshoot the 6 volts a little and do the final adjustment
with L30. If the problem persists, check the capacitor values in the
VFO Range Select area - see te schematic to identify the capacitors
Hi Everyone,
When I could not get the VCO to lock despite changing the number of
turns on the red winding of T5, I got discouraged, and left the assembly
of my K2 in abeyance for a couple of years. However, recently I resumed
work on it.
I started checking voltages and found that line 4V
Hi Everyone,
Success at last!!
I could not wait until tomorrow to adjust T5. I checked everything in
the advice received from Gary Surrency, removed the 17th turn on the red
winding of T5, and then found the locking voltage could be adjusted by
L30 at 4.000 MHz. I have noted the voltage at
Ok, I'm at VCO alignment now :)
Problem is that moving L30's slug around doesn't change the reading on R30, it
stays at 8V. My T5 *looks* good to me. The manual says refer to troubleshooting
but I didn't see anything there that would get me in the ballpark.
I've checked solder joints in the
I’m on page 61 - VCO Alignment where you adjust Inductor L30 until the
voltage at R30 reads 6.0 volts
L30 is at the top stop and the lowest I can get is 6.3 volts. I spread
the turns on T5 as wide as possible to get this low. T5 has 16 turns. Do
I need to remove a turn to bring L30 back
Eric,
First, since the voltage at R30 apparently moves with adjustment of L30,
things are working, but the VFO is not at the correct frequency.
First things to check are the capacitors and Varicaps to be certain you have
the 'right ones in the right holes'. Look at the RF board schematic sheet
Wayne,
With only that small amount of difference, you are not likely to encounter
any problem even though your BFO low end of the range is a bit high - yes, a
60 Hz difference with an uncalibrated 4 MHz reference is 'splitting
straws' - you may want to check it later 'just for reference', but as
S/N 04858 is thru the 40m receiver test [Alignment and Test, Part II].
The only problem [after replacing 10 uH L31 with 12 uH to get sufficient range
of 4 MHz Osc. Cal.] was when I performed the VCO Voltage Readings.
The voltage readings were well in range, but two bands [20 17 m] had
I'm stuck again fellas. I'm on the Part II Alignment and Test. Everything was
going so well
4 MHz Oscillator Calibration..passed
PLL Reference Oscillator Range Test...passed
VCO 8-10 MHz Test. passed
VCO 6 V
Paul,
8 volts on R30 usually means the VCO is not oscillating. Try your counter
probe on TP1 to see if there is any frequency indicated - if so, check that
the frequency is correct for the band you are on (likely 40 meters at this
stage of construction) - the low band edge frequencies are
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