K2 VCO Alignment only 0.02V @ R30

[JeremyJones]

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 should have 6V only has 0.02V.

Below is the email chain (bottom to top) with the trouble shooting Gary and I went through.  Wonder if anyone has any ideas of what the issue might be, or further trouble shooting steps to isolate the problem.

Thanks,
Jeremy


From Jeremy
To Gary
Adjusting the windings on T5 and moving the slug in T30 up has given me 11914khz on 40m. The other bands are still way off. Cal PLL still gives error 232. I've tried running it at 7000, 7050, and 7100khz. Checked the diodes and all are correct and in the right spot.

Oddly enough I was able to get it to run Cal PLL by turning T30 until I got 12003khz at TP1.  Came across this by forgetting the probe in TP3 and running Cal PLL. Moved the probe to TP1 and adjusted T30 and Cal PLL ran.

C22 only has an adjustment of less than 1khz (12085-12086) @ TP3.
R30 which should have 6V only has 0.02V.

Sent from my iPad

On 2013-02-01, at 5:11 PM, Gary Surrency <[e-mail]> wrote:

The freq. is still too low at TP1. The PLL cannot lock and the VCO will not be on freq. unless it can tune to approximately the freq.'s shown in the VFO Table. Err 232 is what you will see when the TP1 freq. is not close enough for the PLL/VCO to lock onto the expected freq.

Something still seems to be wrong too, with the VCO freq.'s on the upper bands. Too low of freq. means there is either too much inductance or too  much capacitance in the T5 circuit. If it is not T5 and some bands are OK or close to OK, then it is likely that for some reason, there is too much C in the circuit still. This could be from an incorrect cap, a VCO relay is not releasing some of the caps, or the varactor diodes are of the wrong type or are in the wrong places.     Check to see if maybe you mixed up the MV209 diodes with the 1SV149 diodes.

Try expanding the red turns on T5 as much as possible, and turn the slug in L30 so it is near the top of the coil. See if then the VCO freq. will come close enough to the stated freq.'s for the PLL to lock when you do CAL PLL which is done only on 40m. If it is not within about 5-10kHz, CAL PLL will not succeed.
--
73, Gary AB7MY

=========
[e-mail]
Elecraft Technical Support  
 
On 2/1/2013 4:52 PM, Jeremy Jones wrote:
Understand totally on the capability of the radios. We're going to be using them as an easy way to practice and test improvised antennas. And if all goes well ill be passing my civilian amateur exam next week.

Did the hard reset.
U6 pin1 checks out good.
U6 pin 5 is 4v.
RFC 15 shows 2.3ohms.
No marks on any relays.
Removed 1 turn from T5. VCO test now gives 8040khz, which is now in spec.
Still only 20mV on R30.
All capacitors correct according to the VCO table.
Still get error 232 when trying Cal PLL.

New VCO freqs
3500khz = 8067
7000khz = 11734
10100khz = 13820
14000khz = 16559
18068khz = 18407
21000khz = 14847
24890khz = 16558
28000khz = 18405

Those are up from what you said was already high.
What next :)


Sent from my iPad

On 2013-02-01, at 3:38 PM, Gary Surrency <[e-mail]> wrote:

Hi Jeremy,

OK on the civilian call sign. Note that our radios are primarily intended to cover the US ham bands, and there is limited freq. coverage outside of those ranges due to the design of the VCO/PLL. The K2 is not general coverage.

You might first try doing a hard reset by holding down the 4,5,6 buttons all at the same time when the power is turned on. This ensures the IOC sets the freq. boundaries correctly and all of the defaults are set. Release the buttons in 2-3 seconds and then wait about 10 seconds for the INFO 201 initialization to complete normally. This is usually done the first time the rig is turned on, but if it was interrupter or did not complete for some reason, the rig could be in an indeterminate state.

The VCO frequencies you stated are too high. Try expanding the red turns on VCO inductor T5, or if necessary - remove a turn.

Use care to not damage the plated through holes if you do need to remove T5 to rewind it.

 Be sure there is no mistake in ID-ing the caps in the VCO circuit too, and make sure none of the VCO relays have any soldering iron burns to their case, they are not reversed on the PCB, and the pins are well soldered. See the VCO Table again for which caps are used on which bands, and verify those are all correct, and they are well soldered, as well as the VCO relays that switch them. Check each and every part and soldered connection in the VCO / PLL area.

Check that U6 pin 1 (LMC662) on the RF Board moves between 0VDC and about 7.5VDC when you do the PLL range test. If not, there is probably a problem with the little PLL reference oscillator thermistor board, usually a poor connection. Remove the left side panel, front panel and control boards to inspect it better. Reheat or resolder any suspect connections.

Also check that U6 pin 5 (LMC662) in the PLL circuit, is steady at 4.0VDC. If not, the PLL thermistor board has a problem with the RE, RF 10k 1/8w resistors that set this level.

In some cases, RFC15 may be broken, open, or not well soldered. Check it with an ohmmeter to be sure it shows less than 10 ohms across its leads. If it is open, the rig will work fine without it and a jumper in place of RFC15.

<cdiidecb.png>




--
73, Gary AB7MY

=========
[e-mail]
Elecraft Technical Support  
 
On 2/1/2013 3:15 PM, Jeremy Jones wrote:
Hi Gary,

I don't have a civilian callsign yet. These radios were purchased for the Canadian Department of National Defense. The name it was ordered under is likely Roger Rodrigue.

D19 and D20 are not installed. D19 is set to n in the secondary menu.

The frequency reading I am getting at TP1 is as follows
7000khz = 11219
3500khz = 7703
10100khz = 13230
14000khz = 15892
18068khz = 17703
21000khz = 14229
24890khz = 15891
28000khz = 17702

T5 checks out, as I had already rewound it. I have good connectivity to the board with it. All soldering has been checked and reheated to ensure no cold joints.  What else should I check or try?

Thanks,
Jeremy

Sent from my iPad

On 2013-02-01, at 11:02 AM, Gary Surrency <[e-mail]> wrote:

Hi Jeremy,

 (Please always provide your call sign. We have 82 customers with the last name of Jones, and I could not find any of them with a first name of Jeremy.)

Sounds like a fault in the VCO circuit and the PLL is not locked on freq. You need to check to see if there is a proper signal freq. at TP1 when the rig is tuned to the bottom  of the 40m band and all other bands, as shown in the VCO Table below. If not, then check T5 and all of the other parts in the VCO circuit.

Make sure D19 and D20 are *not* installed, and the "d19" entry in the Secondary Menu is be set to "n", not to "Y". These parts and the d19 setting are for the K60XV option.

<ifhdegcb.png>
--
73, Gary AB7MY

=========
[e-mail]
Elecraft Technical Support  
 
On 1/31/2013 8:13 PM, Jeremy Jones wrote:
Good day,

I am having a little trouble in the part 2 alignment and test of the K2 I am building (I can't seem to find the serial number sticker at the moment, but it was just purchased).  
When trying to adjust C22 to calibrate the PPL Reference Oscillator, I get no change from adjusting C22.  I read that this might require a CAL FIL and CAL PLL.  I did CAL FIL but CAL PLL give me an Error 232, even when tuned at various points on 40M.

The 4MHz range test is fine, with a high freq of 12099.33 and a low of 12086.53.  

My reading on the VCO test is low at 7694.39.

I am only get 20mV at R30, and no adjustment from L30.

Doing the signal trace at the end of the manual resulted in 628mV for the Reference Oscillator output at pin 1 of U4.  This reading should be between 0.8-1.8Vrms.  All other readings for the Reference Oscillator, VCO and BFO were within specs given.

I have tried numerous tests and checks that I've found on the internet, however nothing seems to address the low voltage at R30, which I think may be the cause of the other issues.  The voltages on U6 are correct, except for pin 7 which is 20mV, which makes me suspect that might be the problem.

Can you offer any other trouble shooting steps or measurements that may help me isolate the issue.  Its been a great build up until now.

Thanks,
Jeremy

[Don Wilhelm-4]

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 do the procedures stated in the K2 Dial
Calibration article there.

Taking things one step at a time - is the PLL Range correct at TP3? Tap
BAND+ to bring it to the highest frequency (about 12100 kHz) then tap
BAND- to get to the lower limit (about 12087 kHz)  Those frequencies can
vary by 2 to 3 kHz from the target values and still be OK.

Once assured that the PLL Range is correct, then tackle the VFO frequencies.
You do have something wrong there because your frequencies are too low
on all bands.  That indicates either too much capacity or too much
inductance is present in the VFO circuit.  Look at the schematic for RF
Board sheet 1.  The area in question is in the upper right corner - the
input side of Q18 - as well as the VFO range Select components.

Is T5 wound on a yellow core?  If wound on a red core, it will have too
much inductance.  Does L30 have a slot across the entire diameter of the
tuning slug?  It should.
Look at the tops of D23, D24, D25 and D26.  They should have a top shape
like Q18 and about the same size.  D21 and D22 should have a smaller
body profile when viewed from the top.  The wider flat side of all those
varactors should be facing toward the rear of the RF Board.

Your next step is to check the relays K13, 14 and 15.  The white stripe
should be on the end toward the rear of the RF board.

Examine the bottom of the board for the soldering of those components in
the VFO and VFO Range Select areas to be certain there are no tiny
solder bridges.

If everything is correct, it *should* have close the frequencies listed
in VCO Table on the Schematic Key page - within 3 to 5 kHz when
everything is correct.

73,
Don W3FPR



On 2/2/2013 9:43 AM, JeremyJones wrote:

> 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
> should have 6V only has 0.02V.
>
> Below is the email chain (bottom to top) with the trouble shooting Gary and
> I went through.  Wonder if anyone has any ideas of what the issue might be,
> or further trouble shooting steps to isolate the problem.
>
> Thanks,
> Jeremy
>
>

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[JeremyJones]

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 correct part, and all diodes have been checked to ensure the correct part and placement.
Soldering has been checked.
Verified C67, C65, C64, C68, D13, Q18 for value and orientation.
Relays click when changing bands.

Still getting the following readings.
3500 = 8248.42
7000 = 12010.78
10100 = 14157.67
14000 = 16976.67
18068 = 18878.23
21000 = 15211.55
24890 = 16977.38
28000 = 18878.84

I am at a loss for what to look for next. Everything seems to check out, but my readings are still off. Anyway I can try to isolate a faulty component?

[Don Wilhelm-4]

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 FCTR, turn the slug on L30 Without
moving the VFO knob) to see if the frequency moves.  If it does not,
re-flow the soldering on the pins of L30.  If the frequency does move,
then T5 and L30 are properly connected, and that is what I wanted you to
check.
Go to the secondary menu (tap DISPLAY) and check the parameter for D19 -
it must be "n".

When re-flowing the solder, use a hot (750 degF) iron and add just a
tiny dab of solder - you actually only need to add a bit of flux.
Watch the solder to be certain it flows out fully onto both the solder
pad and the lead.  If you can see a distinct edge to the solder on the
pad, that connection is suspect - it did not receive enough heat or was
not heated long enough.

If all was as expected for the tests above, inspect the pins of relays
K13, 14 and 15 carefully - you are looking for any whisker of solder
that would form a bridge between two pins.

Next, move your search to the left of the VFO on the schematic, and
check all the components in the U6B circuit for correct values and good
soldering.  Make certain all components are in the proper holes -
sometimes there is a via hole next to a solder pad and the component
lead can be placed in the via hole instead of the solder pad.  When you
have finished that inspection, power on and check the voltage at U6 pin
5.  If it is not 4 volts, you have a problem on the small thermistor board.

73,
Don W3FPR


On 2/2/2013 11:31 AM, Jeremy Jones wrote:

> 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 correct part, and all diodes have been checked to ensure the correct part and placement.
> Soldering has been checked.
> Verified C67, C65, C64, C68, D13, Q18 for value and orientation.
> Relays click when changing bands.
>
> Still getting the following readings.
> 3500 = 8248.42
> 7000 = 12010.78
> 10100 = 14157.67
> 14000 = 16976.67
> 18068 = 18878.23
> 21000 = 15211.55
> 24890 = 16977.38
> 28000 = 18878.84
>
> I am at a loss for what to look for next. Everything seems to check out, but my readings are still off. Anyway I can try to isolate a faulty component?
>
> Sent from my iPad
>
> On 2013-02-02, at 10:38 AM, Don Wilhelm <[hidden email]> wrote:
>
>> 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 do the procedures stated in the K2 Dial Calibration article there.
>>
>> Taking things one step at a time - is the PLL Range correct at TP3? Tap BAND+ to bring it to the highest frequency (about 12100 kHz) then tap BAND- to get to the lower limit (about 12087 kHz)  Those frequencies can vary by 2 to 3 kHz from the target values and still be OK.
>>
>> Once assured that the PLL Range is correct, then tackle the VFO frequencies.
>> You do have something wrong there because your frequencies are too low on all bands.  That indicates either too much capacity or too much inductance is present in the VFO circuit.  Look at the schematic for RF Board sheet 1.  The area in question is in the upper right corner - the input side of Q18 - as well as the VFO range Select components.
>>
>> Is T5 wound on a yellow core?  If wound on a red core, it will have too much inductance.  Does L30 have a slot across the entire diameter of the tuning slug?  It should.
>> Look at the tops of D23, D24, D25 and D26.  They should have a top shape like Q18 and about the same size.  D21 and D22 should have a smaller body profile when viewed from the top.  The wider flat side of all those varactors should be facing toward the rear of the RF Board.
>>
>> Your next step is to check the relays K13, 14 and 15.  The white stripe should be on the end toward the rear of the RF board.
>>
>> Examine the bottom of the board for the soldering of those components in the VFO and VFO Range Select areas to be certain there are no tiny solder bridges.
>>
>> If everything is correct, it *should* have close the frequencies listed in VCO Table on the Schematic Key page - within 3 to 5 kHz when everything is correct.
>>
>> 73,
>> Don W3FPR
>>
>>
>>
>> On 2/2/2013 9:43 AM, JeremyJones wrote:
>>> 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
>>> should have 6V only has 0.02V.
>>>
>>> Below is the email chain (bottom to top) with the trouble shooting Gary and
>>> I went through.  Wonder if anyone has any ideas of what the issue might be,
>>> or further trouble shooting steps to isolate the problem.
>>>
>>> Thanks,
>>> Jeremy

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[Don Wilhelm-4]

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 L30.  There is a row of 3
pins.  The leftmost pin connects to the adjacent lead of T5.
Solder a wire across those two points as a test.  Then check the
resistance to ground at the rightmost end of that row of 3 pins - it
should be zero.

Let me know what you find.

73,
Don W3FPR

On 2/2/2013 2:48 PM, JeremyJones wrote:

> 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 correct part, and all diodes have been checked to ensure the
> correct part and placement.
> Soldering has been checked.
> Verified C67, C65, C64, C68, D13, Q18 for value and orientation.
> Relays click when changing bands.
>
> Still getting the following readings.
> 3500 = 8248.42
> 7000 = 12010.78
> 10100 = 14157.67
> 14000 = 16976.67
> 18068 = 18878.23
> 21000 = 15211.55
> 24890 = 16977.38
> 28000 = 18878.84
>
> I am at a loss for what to look for next. Everything seems to check out, but
> my readings are still off. Anyway I can try to isolate a faulty component?
>
>

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[JeremyJones]

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 orientation.  U6 pin 5 reads 4V.  Bridged the pins between L30 and T5 and resistance is 0.  Checked before bridging and it was as well, but wanted to be sure.

I am at a loss..

Jeremy

[Don Wilhelm-4]

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, resistance between the leftmost pin
and the rightmost pin.

Technical talk - L30 and the red winding of T5 should result in a lesser
inductance than either of them alone.  It appears as though you have
only T5 in the circuit.  An open winding at L30 would make the frequency
too low - your present condition.
The reason for the request of the DC voltages at U4 and U6 is to
determine if U6 is operating as expected and there is the expected drops
between U4 pin 13 and U6 pin 6.

73,
Don W3FPR

On 2/2/2013 5:46 PM, JeremyJones wrote:

> 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
> orientation.  U6 pin 5 reads 4V.  Bridged the pins between L30 and T5 and
> resistance is 0.  Checked before bridging and it was as well, but wanted to
> be sure.
>
> I am at a loss..
>
> Jeremy
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/K2-VCO-Alignment-only-0-02V-R30-tp7569523p7569541.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
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[JeremyJones]

U4 pin13 = 5.029V
U6 pin6 = 5.026V
U6 pin7 = 0.020V

L30 with 1 red lead removed = 0.5ohm

[Don Wilhelm-4]

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).  Make certain pins 5, 6 and 7 of U4 are properly
soldered.  Do the DC voltage checks on U4 and let me know the results.

73,
Don W3FPR

On 2/2/2013 6:42 PM, JeremyJones wrote:

> 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.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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>

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[JeremyJones]

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
Pin14 = 5.029
Pin15 = 5.029
Pin16 = 5.029

Pins 1, 2, 7, 8, 12, and 13 are not within the specs in the manual.  Is this a bad U4, or should I start tracing backwards?

[JeremyJones]

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 that was removed from T5 earlier to bring everything into spec?

[Don Wilhelm-4]

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
same.  If they are not, then there is a connection problem.

If the U7 pin 2 and the U4 pin 5 voltages are the same, I would suggest
a replacement of U4 may be in order - but first check for a solder
bridge across C87 - that would drag the U4 pins 1 and 2 voltages down to
close to zero.

73,
Don W3FPR
On 2/2/2013 7:56 PM, JeremyJones wrote:

> 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
> Pin14 = 5.029
> Pin15 = 5.029
> Pin16 = 5.029
>
> Pins 1, 2, 7, 8, 12, and 13 are not within the specs in the manual.  Is this
> a bad U4, or should I start tracing backwards?
>
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/K2-VCO-Alignment-only-0-02V-R30-tp7569523p7569548.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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[Don Wilhelm-4]

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 where the
voltage at R30 drops below 8 volts.  Then adjust the turns on T5 to
reduce the voltage, then re-check 4000 and repeat as necessary.

You will find the maximum voltage will be your 8.04 volts, and you will
have to change T5 (or readjust L30) to reduce it.  You will not be able
to see which way to go (compress or spread the T5 turns) with the R30
voltage at 8 volts, reduce the frequency and then it will become
apparent whether spreading the turns or compressing them will reduce the
voltage.  In other words, 'sneak up an getting the 4000 MHz voltage to
6.00 volts.

Once you have 4000 MHz voltage at 6.00 volts, check the low and high end
of all other bands.  You may have to make compromises to get all of them
in range - the 6.00 volts at 4000 kHz is not a hard and fast number, it
is just a target that usually works.

73,
Don W3FPR

On 2/2/2013 8:52 PM, JeremyJones wrote:

> 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 that was removed from T5
> earlier to bring everything into spec?
>
>

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[JeremyJones]

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?

[Don Wilhelm-4]

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 where within the 10 kHz range of the PLL reference oscillator it
happens to be.

I am glad to hear that you now have it working within a reasonable range
- good work.

73,
Don W3FPR

On 2/2/2013 9:18 PM, JeremyJones wrote:
> 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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[JeremyJones]

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 and see if tomorrow brings better luck.  

Thanks for all your help,
Jeremy

[Don Wilhelm-4]

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 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 and see if tomorrow brings better
> luck.
>
> Thanks for all your help,
> Jeremy
>

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[JeremyJones]

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 resistance between U7 pin2 and U4 pin 5 and found about 300k.  Looking at the schematics however, it looks like U4 pin5 is actually connected to U7 pin5 (SDO).  There is less than 1 ohm of resistance between U4 pin5 and U7 pin5, so it would appear that U7 may have an issue.

The other odd thing is that even when there is 5V coming into U4 pin5, the symptoms at R30 (0.020V) and the low band frequencies are still there.  It looks like U7 may provide U4 a clock signal as well.

I was seeing the 8V at R30 after reflowing all of the joints near the PLL Reference.  Could the increase in temperature in the are have triggered the thermistor?

The only thing changed between having the 8V at R30 last night and then losing it was the rewinding of T5 to bring it back up to 16 turns of red.  The continuity checks are good through it, and L30 still changes the frequency when adjusted.

[Don Wilhelm-4]

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 to ground.

U7 feeds U6A which in turn controls the voltage on the PLL varactors.
Your PLL is working just fine, so there is no problem there.
Recheck the resistance between U4 pin 5 and U7 pin 2, or better yet
between U4 pin 5 and pin 24 of U6 over on the Control Board - you should
have close to zero ohms.

73,
Don W3FPR

On 2/3/2013 10:51 AM, JeremyJones wrote:

> 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
> resistance between U7 pin2 and U4 pin 5 and found about 300k.  Looking at
> the schematics however, it looks like U4 pin5 is actually connected to U7
> pin5 (SDO).  There is less than 1 ohm of resistance between U4 pin5 and U7
> pin5, so it would appear that U7 may have an issue.
>
> The other odd thing is that even when there is 5V coming into U4 pin5, the
> symptoms at R30 (0.020V) and the low band frequencies are still there.  It
> looks like U7 may provide U4 a clock signal as well.
>
> I was seeing the 8V at R30 after reflowing all of the joints near the PLL
> Reference.  Could the increase in temperature in the are have triggered the
> thermistor?
>
> The only thing changed between having the 8V at R30 last night and then
> losing it was the rewinding of T5 to bring it back up to 16 turns of red.
> The continuity checks are good through it, and L30 still changes the
> frequency when adjusted.
>
>

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[JeremyJones]

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 checks on the control board that Q1 collector should be great than 1M, but is reading 5k.