K2: Can't get frequency counter to work on TP2

[Spence Wilhelm-2]

Hi,

I finished construction of my K2 (serial #5400) last month and all was
working well.  At the time of construction all of the filter alignment went
well.  It has been lots of fun... I'm selling my Yaesu.  :-)

Since then I decided to calibrate the VFO on my K2 to get the frequency
better aligned.  I don't have an accurate frequency generator so followed
the instructions in the manual and used WWV as my source.  That all went
fine but when I went into Cal Fil and wanted to make a change to one of the
filters got an 'info 230' message.  I searched the list and found that was
related to the microprocessor not seeing the BFO frequency during a CAL
FIL.  I verified that the frequency probe works by doing a CAL FCTR with the
probe on TP1.  When I move it to TP2 it always shows 00000.00.  When I first
aligned it last month it worked but not now.

So... I checked the following...  I verified that Q24 is getting turned on
via V ALC when CAL FCTR is enabled.  I see 7.26V DC when V ALC is on, zero
otherwise.

Used my RF probe to find the following RMS voltages for Q24.

V ALC On
Q24  drain        5.99 V
Q24  source      2.02 V
Q24 gate          0 V

V ALC off
Q24  drain     9 mv
Q24  source 15 mV
Q24  gate       0 V


It looks like the FET is turning on and off according to V ALC.  I used my
scope to look at TP2 and can see a nicely formed wave form at around 4Mhz,
But can't detect it with the internal frequency counter and probe.  So to
verify the probe and counter works I used the frequency probe to verify
04913.34 MHz on pin 6 of U11  but it shows 00000.00 when moved back to TP2
Really confusing...

Nothing jumps out at me.  Its been years since I did any serious
troubleshooting. :-)  Anybody have any ideas about what I can do?

73,

Carroll (W7CSW)
_______________________________________________
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

[Don Wilhelm-3]

Carroll,

Unless you are using someone else's email, it is neat to know that there is
another Wilhelm in the K2 family - I started with SN 20 and it is still
going strong.

If your RF Probe is anywhere near correct, it would seem that you have
plenty of RF signal at TP2, so the problem must be in the counter itself.
In the long past, there were problems with the gain of the  2N5179
transistors Q9 and Q10 on the control board - we thought that problem had
been squashed, but perhaps it has reared its ugly head again.  As a side
note, I had purchased some stock 2N5179 transistors, (Fairchild
manufacture), and found that they do not work well in the counter input
circuit either, so that circuit is evidently sensitive to the transistor
type and one 2N5179 is not necessarily like another for that application.

If you have some 2N2222s around your workbench, try replacing the 2N5179s
with 2N2222s.  The counter high frequency limit may be reduced a bit, but if
it is only used internally in the K2, the 40 MHz limit is not required, the
highest frequency needed is less than 25 MHz.  Contact [hidden email]
and I am certain you can have replacement transistors on their way to you.

Just a side note - in your measurements of RF Voltage at Q24, it would seem
that you crossed the gate and drain voltages.  Check the lead orientation on
the K2 schematic key and let us know if there was no typo.  If you are truly
getting RF Voltage on the drain, Q24 may be the problem (but then the K2
would have no transmit output in that case)

73,
Don W3FPR

> -----Original Message-----
>
> I finished construction of my K2 (serial #5400) last month and all was
> working well.  At the time of construction all of the filter
> alignment went
> well.  It has been lots of fun... I'm selling my Yaesu.  :-)
>
> Since then I decided to calibrate the VFO on my K2 to get the frequency
> better aligned.  I don't have an accurate frequency generator so followed
> the instructions in the manual and used WWV as my source.  That all went
> fine but when I went into Cal Fil and wanted to make a change to
> one of the
> filters got an 'info 230' message.  I searched the list and found that was
> related to the microprocessor not seeing the BFO frequency during a CAL
> FIL.  I verified that the frequency probe works by doing a CAL
> FCTR with the
> probe on TP1.  When I move it to TP2 it always shows 00000.00.
> When I first
> aligned it last month it worked but not now.
>
> So... I checked the following...  I verified that Q24 is getting turned on
> via V ALC when CAL FCTR is enabled.  I see 7.26V DC when V ALC is on, zero
> otherwise.
>
> Used my RF probe to find the following RMS voltages for Q24.
>
> V ALC On
> Q24  drain        5.99 V
> Q24  source      2.02 V
> Q24 gate          0 V
>
> V ALC off
> Q24  drain     9 mv
> Q24  source 15 mV
> Q24  gate       0 V
>
>
> It looks like the FET is turning on and off according to V ALC.  I used my
> scope to look at TP2 and can see a nicely formed wave form at around 4Mhz,
> But can't detect it with the internal frequency counter and probe.  So to
> verify the probe and counter works I used the frequency probe to verify
> 04913.34 MHz on pin 6 of U11  but it shows 00000.00 when moved back to TP2
> Really confusing...
>
> Nothing jumps out at me.  Its been years since I did any serious
> troubleshooting. :-)  Anybody have any ideas about what I can do?
>
> 73,
>
> Carroll (W7CSW)
> _______________________________________________
> 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: 7.1.394 / Virus Database: 268.10.4/401 - Release Date: 7/26/2006
>
>

_______________________________________________
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

[johnny-52]

Hi Don,

I do not have any power meter which can measure any RF power output less
than 1 watt.  Could you please advise the minimum output power level of K2
with the power knot fully CCW?

BTW, under the SEC menu of K2, the transverter output (without the
installation of KV60) can be lowered to 0.1 watt.  Would this be the lowest
level output of K2?

I encounter some problems in building my XV144 and am in communication with
Gary.  He is very responsive and helpful.  Upon solving the problem, I
shall come back to this reflector again and let other members know my
experience.

TNX & 73

Johnny Siu VR2XMC


_______________________________________________
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

[Spence Wilhelm-2]

Don,

You are a genius!  Thanks your suggestion worked.  I replaced Q9/Q10
with spare 2N2222s and the counter started working again.  Thank you!

73,

Carroll --- W7CSW


On 7/27/06, Don Wilhelm <[hidden email]> wrote:

> Carroll,
>
> Unless you are using someone else's email, it is neat to know that there is
> another Wilhelm in the K2 family - I started with SN 20 and it is still
> going strong.
>
> If your RF Probe is anywhere near correct, it would seem that you have
> plenty of RF signal at TP2, so the problem must be in the counter itself.
> In the long past, there were problems with the gain of the  2N5179
> transistors Q9 and Q10 on the control board - we thought that problem had
> been squashed, but perhaps it has reared its ugly head again.  As a side
> note, I had purchased some stock 2N5179 transistors, (Fairchild
> manufacture), and found that they do not work well in the counter input
> circuit either, so that circuit is evidently sensitive to the transistor
> type and one 2N5179 is not necessarily like another for that application.
>
> If you have some 2N2222s around your workbench, try replacing the 2N5179s
> with 2N2222s.  The counter high frequency limit may be reduced a bit, but if
> it is only used internally in the K2, the 40 MHz limit is not required, the
> highest frequency needed is less than 25 MHz.  Contact [hidden email]
> and I am certain you can have replacement transistors on their way to you.
>
> Just a side note - in your measurements of RF Voltage at Q24, it would seem
> that you crossed the gate and drain voltages.  Check the lead orientation on
> the K2 schematic key and let us know if there was no typo.  If you are truly
> getting RF Voltage on the drain, Q24 may be the problem (but then the K2
> would have no transmit output in that case)
>
> 73,
> Don W3FPR
>
>
> > -----Original Message-----
> >
> > I finished construction of my K2 (serial #5400) last month and all was
> > working well.  At the time of construction all of the filter
> > alignment went
> > well.  It has been lots of fun... I'm selling my Yaesu.  :-)
> >
> > Since then I decided to calibrate the VFO on my K2 to get the frequency
> > better aligned.  I don't have an accurate frequency generator so followed
> > the instructions in the manual and used WWV as my source.  That all went
> > fine but when I went into Cal Fil and wanted to make a change to
> > one of the
> > filters got an 'info 230' message.  I searched the list and found that was
> > related to the microprocessor not seeing the BFO frequency during a CAL
> > FIL.  I verified that the frequency probe works by doing a CAL
> > FCTR with the
> > probe on TP1.  When I move it to TP2 it always shows 00000.00.
> > When I first
> > aligned it last month it worked but not now.
> >
> > So... I checked the following...  I verified that Q24 is getting turned on
> > via V ALC when CAL FCTR is enabled.  I see 7.26V DC when V ALC is on, zero
> > otherwise.
> >
> > Used my RF probe to find the following RMS voltages for Q24.
> >
> > V ALC On
> > Q24  drain        5.99 V
> > Q24  source      2.02 V
> > Q24 gate          0 V
> >
> > V ALC off
> > Q24  drain     9 mv
> > Q24  source 15 mV
> > Q24  gate       0 V
> >
> >
> > It looks like the FET is turning on and off according to V ALC.  I used my
> > scope to look at TP2 and can see a nicely formed wave form at around 4Mhz,
> > But can't detect it with the internal frequency counter and probe.  So to
> > verify the probe and counter works I used the frequency probe to verify
> > 04913.34 MHz on pin 6 of U11  but it shows 00000.00 when moved back to TP2
> > Really confusing...
> >
> > Nothing jumps out at me.  Its been years since I did any serious
> > troubleshooting. :-)  Anybody have any ideas about what I can do?
> >
> > 73,
> >
> > Carroll (W7CSW)
> > _______________________________________________
> > 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: 7.1.394 / Virus Database: 268.10.4/401 - Release Date: 7/26/2006
> >
> >
>
>

_______________________________________________
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