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Alignment of VCO - Problem

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David C Dawson-2

Alignment of VCO - Problem

Hi,
I am at the stage in building my K2 on page 60 in the VCO test.
Up to this stage all was well.
Now, with the probe _definitely_ connected to TP1. I get a reading of
all zeros.

Does anybody know the trouble-shooting procedure?
Thanks.

(I didn't do the calibration of C22, due to not having a frequency
counter, but the reading was withing range)
--
David Dawson

The greatest dangers to liberty lurk in insidious encroachment by men
of zeal, well-meaning but without understanding.
-- Justice Louis D. Brandeis

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ON4WIX

Re: Alignment of VCO - Problem

Hi David

Are you sure you wired the test probe connector (the white plastic thingy)
correctly? I made the mistake of swapping the wires in the connector and the
result was exactly as you described.
Check the drawing of the connector in the manual carefully to see you didn't
swap the braid and the inner conductor contacts.

Hope this helps.

73 and enjoy building your radio

Glenn ON4WIX
----- Original Message -----
From: "David C Dawson" <[hidden email]>
To: <[hidden email]>
Sent: Monday, November 13, 2006 5:17 AM
Subject: [Elecraft] Alignment of VCO - Problem

> Hi,
> I am at the stage in building my K2 on page 60 in the VCO test.
> Up to this stage all was well.
> Now, with the probe _definitely_ connected to TP1. I get a reading of
> all zeros.
>
> Does anybody know the trouble-shooting procedure?
> Thanks.
>
> (I didn't do the calibration of C22, due to not having a frequency
> counter, but the reading was withing range)
> --
> David Dawson
>
> The greatest dangers to liberty lurk in insidious encroachment by men
> of zeal, well-meaning but without understanding.
> -- Justice Louis D. Brandeis
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>

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Don Wilhelm-3

RE: Alignment of VCO - Problem

In reply to this post by David C Dawson-2

David,

First thing is to verify the probe. Did the probe test give a correct
reading of 4 MHz when it was checked in the 3rd step on page 46 of the
manual? Note that this only checks the operation of the probe and has
nothing to do with proper setting of the 4 MHz reference oscillator.

If your probe did NOT read the 4 MHz oscillator, look for the problem with
your probe - is it connected properly, the shield should be closest to the
left side panel when plugged in.

If your probe DID do the 4 MHz test OK, then let us know and we may be able
to help find the reason your VCO is not functioning properly. Tell us what
test equipment you have available, and if you do not have an oscilloscope or
other means of reading RF Voltages, please build the RF Probe - parts are
provided with the K2 kit, see appendix E of the manual for the schematic.

73,
Don W3FPR

> -----Original Message-----
> Hi,
> I am at the stage in building my K2 on page 60 in the VCO test.
> Up to this stage all was well.
> Now, with the probe _definitely_ connected to TP1. I get a reading of
> all zeros.
>
> Does anybody know the trouble-shooting procedure?
> Thanks.
>
> (I didn't do the calibration of C22, due to not having a frequency
> counter, but the reading was withing range)
> --
> David Dawson
>

David C Dawson-2

Re: Alignment of VCO - Problem

I don't know. Must be asleep at the switch.
Here's what's what so far this end.
The probe verifies -- it did read correctly in step 3 on page 46.
The leads are correct.

I have replaced the suspect diode but the probe will not read anything
at TP1.

I have constructed the RF Probe and connected it to my DMM.
It reads voltages at certain points, but sees nothing at TP1.

On Mon, Nov 13, 2006 at 08:21:51PM -0500, Don Wilhelm wrote:

> David,
>
> First thing is to verify the probe. Did the probe test give a correct
> reading of 4 MHz when it was checked in the 3rd step on page 46 of the
> manual? Note that this only checks the operation of the probe and has
> nothing to do with proper setting of the 4 MHz reference oscillator.
>
> If your probe did NOT read the 4 MHz oscillator, look for the problem with
> your probe - is it connected properly, the shield should be closest to the
> left side panel when plugged in.
>
> If your probe DID do the 4 MHz test OK, then let us know and we may be able
> to help find the reason your VCO is not functioning properly. Tell us what
> test equipment you have available, and if you do not have an oscilloscope or
> other means of reading RF Voltages, please build the RF Probe - parts are
> provided with the K2 kit, see appendix E of the manual for the schematic.
>
> 73,
> Don W3FPR
>
> > -----Original Message-----
> > Hi,
> > I am at the stage in building my K2 on page 60 in the VCO test.
> > Up to this stage all was well.
> > Now, with the probe _definitely_ connected to TP1. I get a reading of
> > all zeros.
> >
> > Does anybody know the trouble-shooting procedure?
> > Thanks.
> >
> > (I didn't do the calibration of C22, due to not having a frequency
> > counter, but the reading was withing range)
> > --
> > David Dawson
> >
>

--
David Dawson

The greatest dangers to liberty lurk in insidious encroachment by men
of zeal, well-meaning but without understanding.
-- Justice Louis D. Brandeis

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Don Wilhelm-3

RE: Alignment of VCO - Problem

David,

Do you read a proper frequency at TP3? Does the PLL Reference Oscillator
Range test produce the correct frequencies? (see the manual page 60).

If the answer to the above question is YES, then check the winding of T5.
Be certain the turns are correct and the leads are inserted into the correct
holes. Check the tinning and soldering. Check the soldering in the
vicinity of T5 and Q18. What are the RF Voltages that you read at the gate
and source of Q18?

Check the DC Voltages (compare to chart in Appendix E) at U3. What are the
RF Voltages at U3 pin s 3 and 6?

73,
Don W3FPR

> -----Original Message-----
>
> I don't know. Must be asleep at the switch.
> Here's what's what so far this end.
> The probe verifies -- it did read correctly in step 3 on page 46.
> The leads are correct.
>
> I have replaced the suspect diode but the probe will not read anything
> at TP1.
>
> I have constructed the RF Probe and connected it to my DMM.
> It reads voltages at certain points, but sees nothing at TP1.
>
>

David C Dawson-2

Re: Alignment of VCO - Problem

I read 12098.20 down to 12084.54 at TP3 in the PLL Reference Oscillator
Range test.

I checked the windings of T5 very carefully, as well as the resistances
between pads - they appear correct.

The soldering at T5 and Q18 looks good.

The RF Voltages at Q18 are all zero :-( ... Dead?

DC Voltages at U3:
Pin 6: 4.02
Pin 7: 8.02
Pin 8: 0.00

RF Voltages at U3, Pin 3 & 6 are all zero :-(

On Tue, Nov 14, 2006 at 07:24:04AM -0500, Don Wilhelm wrote:

> David,
>
> Do you read a proper frequency at TP3? Does the PLL Reference Oscillator
> Range test produce the correct frequencies? (see the manual page 60).
>
> If the answer to the above question is YES, then check the winding of T5.
> Be certain the turns are correct and the leads are inserted into the correct
> holes. Check the tinning and soldering. Check the soldering in the
> vicinity of T5 and Q18. What are the RF Voltages that you read at the gate
> and source of Q18?
>
> Check the DC Voltages (compare to chart in Appendix E) at U3. What are the
> RF Voltages at U3 pin s 3 and 6?
>
> 73,
> Don W3FPR
>
> > -----Original Message-----
> >
> > I don't know. Must be asleep at the switch.
> > Here's what's what so far this end.
> > The probe verifies -- it did read correctly in step 3 on page 46.
> > The leads are correct.
> >
> > I have replaced the suspect diode but the probe will not read anything
> > at TP1.
> >
> > I have constructed the RF Probe and connected it to my DMM.
> > It reads voltages at certain points, but sees nothing at TP1.
> >
> >
>

--
David Dawson
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Don Wilhelm-3

RE: Alignment of VCO - Problem

David,

The PLL Reference is apparently OK and your problem is in the VCO itself.
The lack of RF voltage says the circuit is not oscillating - but we cannot
declare Q18 dead just yet.

OK, next step is to check the DC voltages at Q18 - compare with the DC
Voltage chart in Appendix E.

Double check T5 against the diagram in the manual page 55 (leads 1 and 3
should come from the top of the core and the green winding must be in the
same direction as the red winding) - if one of the windings is reversed, the
oscillator will not oscillate.

Check the voltage at the drain of Q17 and compare with the DC voltage
chart - measure the gate and source while you are at it, and just for a bit
of additional information, check the DC voltages at Q16.

Tell us what you find.

73,
Don W3FPR

> -----Original Message-----
>
> I read 12098.20 down to 12084.54 at TP3 in the PLL Reference Oscillator
> Range test.
>
> I checked the windings of T5 very carefully, as well as the resistances
> between pads - they appear correct.
>
> The soldering at T5 and Q18 looks good.
>
> The RF Voltages at Q18 are all zero :-( ... Dead?
>
> DC Voltages at U3:
> Pin 6: 4.02
> Pin 7: 8.02
> Pin 8: 0.00
>
> RF Voltages at U3, Pin 3 & 6 are all zero :-(
>
> On Tue, Nov 14, 2006 at 07:24:04AM -0500, Don Wilhelm wrote:
> > David,
> >
> > Do you read a proper frequency at TP3? Does the PLL Reference Oscillator
> > Range test produce the correct frequencies? (see the manual page 60).
> >
> > If the answer to the above question is YES, then check the
> winding of T5.
> > Be certain the turns are correct and the leads are inserted
> into the correct
> > holes. Check the tinning and soldering. Check the soldering in the
> > vicinity of T5 and Q18. What are the RF Voltages that you read
> at the gate
> > and source of Q18?
> >
> > Check the DC Voltages (compare to chart in Appendix E) at U3.
> What are the
> > RF Voltages at U3 pin s 3 and 6?
> >
> > 73,
> > Don W3FPR
> >
> > > -----Original Message-----
> > >
> > > I don't know. Must be asleep at the switch.
> > > Here's what's what so far this end.
> > > The probe verifies -- it did read correctly in step 3 on page 46.
> > > The leads are correct.
> > >
> > > I have replaced the suspect diode but the probe will not read anything
> > > at TP1.
> > >
> > > I have constructed the RF Probe and connected it to my DMM.
> > > It reads voltages at certain points, but sees nothing at TP1.
> > >
> > >
> >
>
> --
> David Dawson
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.1.409 / Virus Database: 268.14.5/533 - Release Date: 11/13/2006
>
>

David C Dawson-2

Re: Alignment of VCO - Problem

Thanks,
Here's the measurements.
Note: the transistors are quite close to the board, so I had to figure
out which adjacent pad to tap; I think I have measured correctly.

The DC Voltages at Q18 are:

Point Measured Chart
----- -------- -----
Gate: 0.00 -1.0
Source: 3.19 2 to 3
Drain: 8.02 6.3

!

Q16:

Point Measured Chart
----- -------- -----
Emitter: 0 0.0
Base: 0 0.6
Collector: 7.98 2.2

!!

T5 is correct according to the diagram on page 55; leads 1 and 3 come
from the top of the core and leads 2 and 4 come from the bottom, and I
think that being so, the green winding cannot be reversed.

On Tue, Nov 14, 2006 at 03:56:31PM -0500, Don Wilhelm wrote:

> David,
>
> The PLL Reference is apparently OK and your problem is in the VCO itself.
> The lack of RF voltage says the circuit is not oscillating - but we cannot
> declare Q18 dead just yet.
>
> OK, next step is to check the DC voltages at Q18 - compare with the DC
> Voltage chart in Appendix E.
>
> Double check T5 against the diagram in the manual page 55 (leads 1 and 3
> should come from the top of the core and the green winding must be in the
> same direction as the red winding) - if one of the windings is reversed, the
> oscillator will not oscillate.
>
> Check the voltage at the drain of Q17 and compare with the DC voltage
> chart - measure the gate and source while you are at it, and just for a bit
> of additional information, check the DC voltages at Q16.
>
> Tell us what you find.
>
> 73,
> Don W3FPR

David Dawson
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Don Wilhelm-3

RE: Alignment of VCO - Problem

David,

The voltage measurements at Q17 please!

73,
Don W3FPR

> -----Original Message-----
> Thanks,
> Here's the measurements.
> Note: the transistors are quite close to the board, so I had to figure
> out which adjacent pad to tap; I think I have measured correctly.
>
>
> The DC Voltages at Q18 are:
>
> Point Measured Chart
> ----- -------- -----
> Gate: 0.00 -1.0
> Source: 3.19 2 to 3
> Drain: 8.02 6.3
>
> !
>
> Q16:
>
> Point Measured Chart
> ----- -------- -----
> Emitter: 0 0.0
> Base: 0 0.6
> Collector: 7.98 2.2
>
> !!
>
>
>
> T5 is correct according to the diagram on page 55; leads 1 and 3 come
> from the top of the core and leads 2 and 4 come from the bottom, and I
> think that being so, the green winding cannot be reversed.
>
>

David C Dawson-2

Re: Alignment of VCO - Problem

Don,
OOPS!
Here are the measurements on Q17:

Point Measured Chart
----- -------- -----
Gate: 2.17 2.2
Source: - 0.0
Drain: 1.97 2to3
On Tue, Nov 14, 2006 at 09:09:43PM -0500, Don Wilhelm wrote:

> David,
>
> The voltage measurements at Q17 please!
>
> 73,
> Don W3FPR
>
> > -----Original Message-----
> > Thanks,
> > Here's the measurements.
> > Note: the transistors are quite close to the board, so I had to figure
> > out which adjacent pad to tap; I think I have measured correctly.
> >
> >
> > The DC Voltages at Q18 are:
> >
> > Point Measured Chart
> > ----- -------- -----
> > Gate: 0.00 -1.0
> > Source: 3.19 2 to 3
> > Drain: 8.02 6.3
> >
> > !
> >
> > Q16:
> >
> > Point Measured Chart
> > ----- -------- -----
> > Emitter: 0 0.0
> > Base: 0 0.6
> > Collector: 7.98 2.2
> >
> > !!
> >
> >
> >
> > T5 is correct according to the diagram on page 55; leads 1 and 3 come
> > from the top of the core and leads 2 and 4 come from the bottom, and I
> > think that being so, the green winding cannot be reversed.
> >
> >

David C Dawson-2

Re: Alignment of VCO - Problem

Double-checking DC voltage measurements on 3 transistors.

Item Measured Chart
Q18
---
G: 0.00 -1.0 !!
S: 1.97 ** 2to3
D: 7.97 6.3 !

Q17
---
G: 2.16 * 2.2
S: 0.00 0.0
D: 1.97 ** 2to3

Q16
---
E: 0.00 0.0
B: 0.55 0.6
C: 2.16 * 2.2
--
David Dawson

The greatest dangers to liberty lurk in insidious encroachment by men
of zeal, well-meaning but without understanding.
-- Justice Louis D. Brandeis

_______________________________________________
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Post to: [hidden email]
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Don Wilhelm-3

RE: Alignment of VCO - Problem

David,

All those voltages are about right for a VFO that is not oscillating. Do
not be concerned about a voltage that is only a few 10s of millivolts
different from the chart. Actual readings will vary a bit from DMM to DMM.

The important voltage now is the gate of Q18 - it should go negative once
some RF is developed in the gate circuit.

The best I can tell you right now is to turn to the schematic - RF Board
Sheet 1 of 4 and look at the VFO components in the upper right quadrant of
that page. Check the placement and value of each of those components. If
you have trouble physically locating any component, the Parts Placement
diagrams can be helpful. Be certain the diodes are oriented correctly.
Re-check T5, or even rewind it. Be certain the T5 leads are well tinned and
soldered.

73,
Don W3FPR

> -----Original Message-----
>
> Double-checking DC voltage measurements on 3 transistors.
>
> Item Measured Chart
> Q18
> ---
> G: 0.00 -1.0 !!
> S: 1.97 ** 2to3
> D: 7.97 6.3 !
>
> Q17
> ---
> G: 2.16 * 2.2
> S: 0.00 0.0
> D: 1.97 ** 2to3
>
> Q16
> ---
> E: 0.00 0.0
> B: 0.55 0.6
> C: 2.16 * 2.2
> --
> David Dawson
>

Don Wilhelm-3

RE: Alignment of VCO - Problem

In reply to this post by David C Dawson-2

David,

Reviewing your voltage readings with my 2nd cup of tea this morning, I find
Q17 might be giving you a problem. Temporarily short the drain of Q17 to
ground and see if your VFO starts oscillating.

If it does, then Q17 may have been zapped during handling and installation -
those 2N7000s are static sensitive.

73,
Don W3FPR

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]]On Behalf Of David C Dawson
> Sent: Wednesday, November 15, 2006 3:07 AM
> To: [hidden email]
> Subject: Re: [Elecraft] Alignment of VCO - Problem
>
>
> Double-checking DC voltage measurements on 3 transistors.
>
> Item Measured Chart
> Q18
> ---
> G: 0.00 -1.0 !!
> S: 1.97 ** 2to3
> D: 7.97 6.3 !
>
> Q17
> ---
> G: 2.16 * 2.2
> S: 0.00 0.0
> D: 1.97 ** 2to3
>
> Q16
> ---
> E: 0.00 0.0
> B: 0.55 0.6
> C: 2.16 * 2.2
> --
> David Dawson
>
> The greatest dangers to liberty lurk in insidious encroachment by men
> of zeal, well-meaning but without understanding.
> -- Justice Louis D. Brandeis
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.1.409 / Virus Database: 268.14.5/533 - Release Date: 11/13/2006
>
>

David C Dawson-2

Re: Alignment of VCO - Problem

THANKS DON! The problem is solved, and good news - Q17 is fine.

When I got your email, I turned on the rig and put the frequency probe
on TP1. This time it measured a frequency and a correct one at that.

I thought - Before it didn't work. Now it does. Hmmmm...Hmmmm... Aha!
loose connection! So I touched Q17 and off it went, I found a poor
solder joint that my (non) eagle eye missed.

Talk about bone headed screwdriver experts, eh?

On Wed, Nov 15, 2006 at 08:03:06AM -0500, Don Wilhelm wrote:

> David,
>
> Reviewing your voltage readings with my 2nd cup of tea this morning, I find
> Q17 might be giving you a problem. Temporarily short the drain of Q17 to
> ground and see if your VFO starts oscillating.
>
> If it does, then Q17 may have been zapped during handling and installation -
> those 2N7000s are static sensitive.
>
> 73,
> Don W3FPR
>
> > -----Original Message-----
> > From: [hidden email]
> > [mailto:[hidden email]]On Behalf Of David C Dawson
> > Sent: Wednesday, November 15, 2006 3:07 AM
> > To: [hidden email]
> > Subject: Re: [Elecraft] Alignment of VCO - Problem
> >
> >
> > Double-checking DC voltage measurements on 3 transistors.
> >
> > Item Measured Chart
> > Q18
> > ---
> > G: 0.00 -1.0 !!
> > S: 1.97 ** 2to3
> > D: 7.97 6.3 !
> >
> > Q17
> > ---
> > G: 2.16 * 2.2
> > S: 0.00 0.0
> > D: 1.97 ** 2to3
> >
> > Q16
> > ---
> > E: 0.00 0.0
> > B: 0.55 0.6
> > C: 2.16 * 2.2
> > --
> > David Dawson
> >
> > The greatest dangers to liberty lurk in insidious encroachment by men
> > of zeal, well-meaning but without understanding.
> > -- Justice Louis D. Brandeis
> >
> > _______________________________________________
> > Elecraft mailing list
> > Post to: [hidden email]
> > You must be a subscriber to post to the list.
> > Subscriber Info (Addr. Change, sub, unsub etc.):
> > http://mailman.qth.net/mailman/listinfo/elecraft
> >
> > Help: http://mailman.qth.net/subscribers.htm
> > Elecraft web page: http://www.elecraft.com
> >
> >
> > --
> > No virus found in this incoming message.
> > Checked by AVG Free Edition.
> > Version: 7.1.409 / Virus Database: 268.14.5/533 - Release Date: 11/13/2006
> >
> >
>

--
David Dawson

A strong conviction that something must be done is the parent of many
bad measures.
-- Daniel Webster

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Don Wilhelm-3

RE: Alignment of VCO - Problem

David,

Don't feel too bad - it happens to lots of folks. This is the 3rd instance
that I recall in the last 2 days where the problem turned out to be a bad
solder connection. It is by far the most common problem encountered by
builders. So much so that I often say "Check the soldering, and then
re-check the soldering, and when you have finished that - check the
soldering".

73,
Don W3FPR

> -----Original Message-----

>
> THANKS DON! The problem is solved, and good news - Q17 is fine.
>
> When I got your email, I turned on the rig and put the frequency probe
> on TP1. This time it measured a frequency and a correct one at that.
>
> I thought - Before it didn't work. Now it does. Hmmmm...Hmmmm... Aha!
> loose connection! So I touched Q17 and off it went, I found a poor
> solder joint that my (non) eagle eye missed.
>
> Talk about bone headed screwdriver experts, eh?
>