RE: Frequency Counter Probe not working S/N 5567

[McMillan, Terry]

Good Morning Don,

Thanks for your assistance, I found the problem and the Freq. counter is
now working.

I used one of the 2n2222's from the RF board and replaced Q9.  But, this
did not fix the problem so I checked the voltage at the base and Q9 and
found none.  Checking the voltage at Q10 I found .73Vdc.  Checked for
voltage at RP4 pin 1 and found none, checked RP4 pin 2 and found
3.something.  Reheated pins 1 and 2 and bang problem fixed, .73Vdc at Q9
base and freq. counter working.

Thanks for your help.  It's been a long time since I followed a
schematic.  All in all a good learning experience.  Now back to
building.

Have a great week.

Terry
VA6MAC
s/n 5567

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Tuesday, July 04, 2006 3:33 PM
To: McMillan, Terry
Subject: RE: [Elecraft] Frequency Counter Probe not working S/N 5567


Terry,

I don't know the RF characteristics of those replacement transistors, so
I would be hesitant to use them in an RF application - I suggest you use
the 2N2222s that are intended for RF Board Q11 and Q13 as your
replacements for the MPS5179s and then use the NTE123AP transistors for
Q11 and Q13 - they will owrk in those positions just fine becuase they
do not handle RF, so only the DC gain counts, and if they are good
replacements, they will work there because that circuit only sets the
bias level for the PA output transistors.

Hey, at 11 cents each, buy 9 of them for $1 and you will have a few
spares!!!

73,
Don W3FPR

> -----Original Message-----
> From: McMillan, Terry [mailto:[hidden email]]
> Sent: Tuesday, July 04, 2006 5:11 PM
> To: [hidden email]
> Subject: RE: [Elecraft] Frequency Counter Probe not working S/N 5567
>
>
>
> Don,
>
> I called the local electronics shop they could not find a cross
> reference for Q9/Q10 MPS5179.  But have a cross reference for 2n2222,
> a NTE123AP.
>
> At 11 cents each can I use the NTE123AP to replace Q9/Q10?  This would

> save shipping from the US to Canada and I can walk over to the shop so

> delivery is quick.
>
> Thanks again for your help.
>
> Terry VA6MAC
>
> -----Original Message-----
> From: Don Wilhelm [mailto:[hidden email]] Sent: Monday, July 03,
> 2006 1:25 PM
> To: McMillan, Terry
> Subject: RE: [Elecraft] Frequency Counter Probe not working S/N 5567
>
>
> Terry,
>
> If you do not have an oscilliscope to check through the Q9/Q10 path to

> the microprocessor input, then yes the next thing to try is replacing
> Q9 and Q10.  If you have stock on 2N2222s, try those in place of the
> 2N5179s.  Note that I have ordered some 2N5179s that did not work
> properly in this application, but all the ones I have obtained from
> Elecraft worked fine - my conclusion is that all 2N5179s are not
> created equal and I don't know why.
>
> You can 'borrow' 2N2222s from the unbuilt part of your K2 and order
> replacements from Scott.
>
> 73,
> Don W3FPR
>
>
> > -----Original Message-----
> > From: McMillan, Terry [mailto:[hidden email]]
> > Sent: Monday, July 03, 2006 12:27 PM
> > To: [hidden email]
> > Subject: RE: [Elecraft] Frequency Counter Probe not working S/N 5567
> >
> >
> >
> > Good Morning Don,
> >
> > Thanks for your help.
> >
> > I verified again that the pins are not reversed in the housing;
> the > shield is closest to the side panel.
> >
> > I then checked c22 with a 12 pf cap connected in series with a
> test > lead, still nothing displayed on the panel except 00000.00.
> Using > another RXvr I do detect a 4MHz signal at C22 so it does look
> like the
>
> > reference oscillator is working. So it would appear to be a
> component > in the counter circuit on the board at fault.
> >
> > I rechecked:
> >
> > Solder bridges - None
> > Q9 & Q10: are MPS5179 and oriented properly
> > RP4: 8x-2-823, I questioned parts@elecraft if this is a sub for
> > "77083823". They confirmed it was.
> > C37: 103
> > C38: 681
> > C39: 103
> >
> > What's next, replace Q9 & Q10?
> >
> > Terry VA6MAC
> >
> > -----Original Message-----
> > From: Don Wilhelm [mailto:[hidden email]] Sent: July 2, 2006
> > 7:41
>
> > PM
> > To: McMillan, Terry; [hidden email]
> > Subject: RE: [Elecraft] Frequency Counter Probe not working S/N 5567
> >
> > Terry,
> >
> > Is there a possibility that you have the pins in the housing
> > reversed?
>
> > The shield should be closest to the side panel.
> >
> > There is just not much to the frequency probe - a piece of coax with

> > a
>
> > 10 pf capacitor in series with the center conductor, so not
> really > much to go wrong.
> >
> > To test the counter (without the probe), you can connect a clip
> lead > with a series 10 pf capacitor from the counter input to the
> control > board (pin furtherest away from the side panel) to C22 (any
> 10 pf cap > will do - use one
> > from the kit, or a 12 pf if you can't find a 10 pf) - if you find a
> > reading anywhere near 4 MHz, then the counter is working and you
> > will find
> your
> > trouble in the probe - or there is a chance that the reference
> > oscillator is not working (and that is a bigger problem).  If you
> > have another
> receiver,
> > connect a short antenna wire and put it close ot C22 to see if you
> > can detect a 4 MHz signal present.  But then, if the microprocessor
> > is responding and you have an LCD display, then the 4 MHz oscillator

> > is likely working.
> >
> > You can continue building, but you will need the counter probe
> when > you begin the Alignment and Test II. I would hesitate to say
> that you > should power up the K2 during the process of building the
> Part II > stuff - if something goes wrong, it is difficult to
> > predict what the problem may be.  Normally, passing the resistance
> > checks is an indicator that it is OK to apply power.
> >
> > 73,
> > Don W3FPR
> >
> >
> > > -----Original Message-----
> > >
> > > I've been busy building my K2.  I have completed the control
> and > > front panel boards with all checks reading as they should.
> Have > > just completed Part I of the RF board and everything checks
> out fine
>
> > > except when I test the frequency counter probe on the left
> side of > > C22 the display does not change from 00000.00.  Tried both

> sides but
>
> > > nothing reads on counter.
> > >
> > > My questions are:
> > >
> > >
> > > Is there something I can do to isolate the problem to either
> the > > probe or the control board?
> > >
> > >
> > > How do I check the bias voltage on Q9 and Q10 ?
> > >
> > >
> > > What can I do to isolate the failing component?
> > >
> > >
> > > Thanks for your help.
> > >
> > >
> > > Oh, one last thing.  Can I carry on with building Part II or
> will > > that get in the way of troubleshooting this problem. Can I
> power up
>
> > > the radio again without completing part II.
> > >
> > >
> > > Terry
> > >
> > > VA6MAC
> > >
> >
> >
> > ********************************************************************
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[Don Wilhelm-3]

Terry,

I'm glad you found it - congratulations on the good troubleshooting steps.

73,
Don W3FPR
 

> -----Original Message-----
>
> Thanks for your assistance, I found the problem and the Freq. counter is
> now working.
>
> I used one of the 2n2222's from the RF board and replaced Q9.  But, this
> did not fix the problem so I checked the voltage at the base and Q9 and
> found none.  Checking the voltage at Q10 I found .73Vdc.  Checked for
> voltage at RP4 pin 1 and found none, checked RP4 pin 2 and found
> 3.something.  Reheated pins 1 and 2 and bang problem fixed, .73Vdc at Q9
> base and freq. counter working.
>
> Thanks for your help.  It's been a long time since I followed a
> schematic.  All in all a good learning experience.  Now back to
> building.
>
>

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