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K2 VCO Alignment T5 L30

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K2bew

K2 VCO Alignment T5 L30

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 voltage check on R30 and
adjusting L30.
VFO frequency set at 4000.00 kHz
I initially got 3.5 volts and bottomed out L30 to get it to 5.5 volts, and
then I over screwed it to try to get that last half a volt and ended
damaging it, so, then I carefully took out L30 and put in a new one.

I also took out T5 and rechecked all the ends for continuity, rewound the
green wire to space it exactly in the middle of the red winding and spaced
everything evenly. I confirmed it is the large yellow core, I have 16 on
the red wire and 4 on the green (by the way the illustration shows 14 turns
of red) . I verified I have R30 as Br-R-Br 120 ohms with both my DVM and by
color, and I verified C72 is 271, and I reflowed the solder on both.
With a new 4.7 inductor (large slot, no red mark) in L30 I now get 2.75
volts on the left side of R30 to start with and it bottoms out at 4.5 volts
(I was very careful to not bottom it out too hard this time and damage this
one, and I have already ordered a couple new ones from Elecraft).

What else can I do to increase that voltage? Would changing the number of
windings on T5 change it enough to get to 6 volts?

Thank you and 73,
Tom Bewick K2BEW
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Don Wilhelm

Re: K2 VCO Alignment T5 L30

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.
I am not sure that is your problem, but it is worthy of checking.

First question is - did you get good frequency readings for the PLL
Reference Oscillator range? If it fails, you see a strange frequency
reading at the high frequency end (when BAND+ is tapped).
Now, the other "funny" thing is that it sometimes checks OK with the
internal counter probe plugged into TP3, but fails when the probe is
removed.

Under those conditions, the PLL and VFO do not lock together

So the first thing to try is to solder a 10 to 15pF capacitor between
the source of Q19 and ground. Then between a combination of adjusting
the red turns on T5 and L30 see if you can obtain the correct R30 voltage.

If that is successful, then all should be well.

If not successful, get a replacement Q19 from Elecraft. Send the part
number and description to [hidden email] and ask for a replacement.

If that does not correct things, then email me and we can go through
some other checks to determine the source of the failure.

73,
Don W3FPR

On 1/18/2019 8:48 AM, K2bew wrote:

> 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 voltage check on R30 and
> adjusting L30.
> VFO frequency set at 4000.00 kHz
> I initially got 3.5 volts and bottomed out L30 to get it to 5.5 volts, and
> then I over screwed it to try to get that last half a volt and ended
> damaging it, so, then I carefully took out L30 and put in a new one.
>
> I also took out T5 and rechecked all the ends for continuity, rewound the
> green wire to space it exactly in the middle of the red winding and spaced
> everything evenly. I confirmed it is the large yellow core, I have 16 on
> the red wire and 4 on the green (by the way the illustration shows 14 turns
> of red) . I verified I have R30 as Br-R-Br 120 ohms with both my DVM and by
> color, and I verified C72 is 271, and I reflowed the solder on both.
> With a new 4.7 inductor (large slot, no red mark) in L30 I now get 2.75
> volts on the left side of R30 to start with and it bottoms out at 4.5 volts
> (I was very careful to not bottom it out too hard this time and damage this
> one, and I have already ordered a couple new ones from Elecraft).
>
> What else can I do to increase that voltage? Would changing the number of
> windings on T5 change it enough to get to 6 volts?
>
> Thank you and 73,
> Tom Bewick K2BEW

K2bew

Re: K2 VCO Alignment T5 L30

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 <[hidden email] wrote:

> 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.
> I am not sure that is your problem, but it is worthy of checking.
>
> First question is - did you get good frequency readings for the PLL
> Reference Oscillator range? If it fails, you see a strange frequency
> reading at the high frequency end (when BAND+ is tapped).
> Now, the other "funny" thing is that it sometimes checks OK with the
> internal counter probe plugged into TP3, but fails when the probe is
> removed.
>
> Under those conditions, the PLL and VFO do not lock together
>
> So the first thing to try is to solder a 10 to 15pF capacitor between
> the source of Q19 and ground. Then between a combination of adjusting
> the red turns on T5 and L30 see if you can obtain the correct R30 voltage.
>
> If that is successful, then all should be well.
>
> If not successful, get a replacement Q19 from Elecraft. Send the part
> number and description to [hidden email] and ask for a replacement.
>
> If that does not correct things, then email me and we can go through
> some other checks to determine the source of the failure.
>
> 73,
> Don W3FPR
>
> On 1/18/2019 8:48 AM, K2bew wrote:
> > 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 voltage check on R30 and
> > adjusting L30.
> > VFO frequency set at 4000.00 kHz
> > I initially got 3.5 volts and bottomed out L30 to get it to 5.5 volts,
> and
> > then I over screwed it to try to get that last half a volt and ended
> > damaging it, so, then I carefully took out L30 and put in a new one.
> >
> > I also took out T5 and rechecked all the ends for continuity, rewound the
> > green wire to space it exactly in the middle of the red winding and
> spaced
> > everything evenly. I confirmed it is the large yellow core, I have 16 on
> > the red wire and 4 on the green (by the way the illustration shows 14
> turns
> > of red) . I verified I have R30 as Br-R-Br 120 ohms with both my DVM and
> by
> > color, and I verified C72 is 271, and I reflowed the solder on both.
> > With a new 4.7 inductor (large slot, no red mark) in L30 I now get 2.75
> > volts on the left side of R30 to start with and it bottoms out at 4.5
> volts
> > (I was very careful to not bottom it out too hard this time and damage
> this
> > one, and I have already ordered a couple new ones from Elecraft).
> >
> > What else can I do to increase that voltage? Would changing the number of
> > windings on T5 change it enough to get to 6 volts?
> >
> > Thank you and 73,
> > Tom Bewick K2BEW
>

K2bew

Re: K2 VCO Alignment T5 L30

In reply to this post by Don Wilhelm

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 red wire of T5.
That got me a voltage of 8.5V on R30 with L30 bottomed out that I was able
to easily back off to a stable 6 volts.
I went ahead and did the voltage tests on the other bands and had a nice
range of 1.844 to 6 volts as my low and high on the VCO.
So, that's all set.

However, new problem. I went on to the test the BFO and I have 0000.04 kHz.
on TP2, so it's not working.
I went to the trouble shooting guide and I have 0.058 Vrms on pin 6 of U11
with the RF probe.
Looking at the archives of the reflector that would indicate that U11 is
bad and I need a replacement, correct? or are there other things I should
look at first?
The good thing is I'm becoming very accustomed to the radio and enjoying
the trouble shooting.
Thanks for all the help, I really appreciate it.

73,
Tom Bewick, K2BEW

On Fri, Jan 18, 2019 at 10:33 AM Don Wilhelm <[hidden email]> wrote:

Ed Pflueger

Re: K2 VCO Alignment T5 L30

I've got good news. I had the wrong Capacitor in the BFO section and just happened to have a replacement for C169. Whoops I told on myself! Any way at TP2 +4917.74 and -4911.90 for a difference of 5.84. Don struck again. Hi Hi.. I'll check the voltages on RP6 tomorrow.

Ed.. AB4IQ

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of K2bew
Sent: Saturday, January 19, 2019 5:35 PM
To: [hidden email]
Cc: Elecraft Mail List <[hidden email]>
Subject: Re: [Elecraft] K2 VCO Alignment T5 L30

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 red wire of T5.
That got me a voltage of 8.5V on R30 with L30 bottomed out that I was able to easily back off to a stable 6 volts.
I went ahead and did the voltage tests on the other bands and had a nice range of 1.844 to 6 volts as my low and high on the VCO.
So, that's all set.

However, new problem. I went on to the test the BFO and I have 0000.04 kHz.
on TP2, so it's not working.
I went to the trouble shooting guide and I have 0.058 Vrms on pin 6 of U11 with the RF probe.
Looking at the archives of the reflector that would indicate that U11 is bad and I need a replacement, correct? or are there other things I should look at first?
The good thing is I'm becoming very accustomed to the radio and enjoying the trouble shooting.
Thanks for all the help, I really appreciate it.

73,
Tom Bewick, K2BEW

On Fri, Jan 18, 2019 at 10:33 AM Don Wilhelm <[hidden email]> wrote:

> 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.
> I am not sure that is your problem, but it is worthy of checking.
>
> First question is - did you get good frequency readings for the PLL
> Reference Oscillator range? If it fails, you see a strange frequency
> reading at the high frequency end (when BAND+ is tapped).
> Now, the other "funny" thing is that it sometimes checks OK with the
> internal counter probe plugged into TP3, but fails when the probe is
> removed.
>
> Under those conditions, the PLL and VFO do not lock together
>
> So the first thing to try is to solder a 10 to 15pF capacitor between
> the source of Q19 and ground. Then between a combination of adjusting
> the red turns on T5 and L30 see if you can obtain the correct R30 voltage.
>
> If that is successful, then all should be well.
>
> If not successful, get a replacement Q19 from Elecraft. Send the part
> number and description to [hidden email] and ask for a replacement.
>
> If that does not correct things, then email me and we can go through
> some other checks to determine the source of the failure.
>
> 73,
> Don W3FPR
>
> On 1/18/2019 8:48 AM, K2bew wrote:
> > 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 voltage check on R30 and
> > adjusting L30.
> > VFO frequency set at 4000.00 kHz
> > I initially got 3.5 volts and bottomed out L30 to get it to 5.5
> > volts,
> and
> > then I over screwed it to try to get that last half a volt and ended
> > damaging it, so, then I carefully took out L30 and put in a new one.
> >
> > I also took out T5 and rechecked all the ends for continuity,
> > rewound the green wire to space it exactly in the middle of the red
> > winding and
> spaced
> > everything evenly. I confirmed it is the large yellow core, I have
> > 16 on the red wire and 4 on the green (by the way the illustration
> > shows 14
> turns
> > of red) . I verified I have R30 as Br-R-Br 120 ohms with both my DVM
> > and
> by
> > color, and I verified C72 is 271, and I reflowed the solder on both.
> > With a new 4.7 inductor (large slot, no red mark) in L30 I now get
> > 2.75 volts on the left side of R30 to start with and it bottoms out
> > at 4.5
> volts
> > (I was very careful to not bottom it out too hard this time and
> > damage
> this
> > one, and I have already ordered a couple new ones from Elecraft).
> >
> > What else can I do to increase that voltage? Would changing the
> > number of windings on T5 change it enough to get to 6 volts?
> >
> > Thank you and 73,
> > Tom Bewick K2BEW
>

______________________________________________________________
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Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email]

______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Don Wilhelm

Re: K2 VCO Alignment T5 L30

In reply to this post by K2bew

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 1/19/2019 6:35 PM, K2bew wrote:

> 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 red wire of T5.
> That got me a voltage of 8.5V on R30 with L30 bottomed out that I
> was able to easily back off to a stable 6 volts.
> I went ahead and did the voltage tests on the other bands and had a
> nice range of 1.844 to 6 volts as my low and high on the VCO.
> So, that's all set.
>
> However, new problem. I went on to the test the BFO and I have 0000.04
> kHz. on TP2, so it's not working.
> I went to the trouble shooting guide and I have 0.058 Vrms on pin 6 of
> U11 with the RF probe.
> Looking at the archives of the reflector that would indicate that U11
> is bad and I need a replacement, correct? or are there other things I
> should look at first?
> The good thing is I'm becoming very accustomed to the radio and
> enjoying the trouble shooting.
> Thanks for all the help, I really appreciate it.
>
> 73,
> Tom Bewick, K2BEW
>

K2bew

Re: K2 VCO Alignment T5 L30

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 components again in that section with the RF board disconnected and
out of the case.
I found much to my chagrin I had not installed D37 and D38! I had them
checked off in the manual as being installed, and I even wrote in pencil in
the margin on the next step where you put the rest of the V149's in the RF
board that I had 2 left over, but I failed to notice I had them left over
because I did not put them in the step before!, good grief.
Anyway I have a high BFO reading of 4917.60 and a low reading of 4911.98
with a difference of 5.62.
Thank you Don and to others that gave suggestions, and I do wish those
having similar problems well in their trouble shooting.

Upward and onward 73,
Tom Bewick, K2BEW

On Sun, Jan 20, 2019 at 8:22 AM Don Wilhelm <[hidden email]> wrote:

> 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 1/19/2019 6:35 PM, K2bew wrote:
> > 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 red wire of T5.
> > That got me a voltage of 8.5V on R30 with L30 bottomed out that I
> > was able to easily back off to a stable 6 volts.
> > I went ahead and did the voltage tests on the other bands and had a
> > nice range of 1.844 to 6 volts as my low and high on the VCO.
> > So, that's all set.
> >
> > However, new problem. I went on to the test the BFO and I have 0000.04
> > kHz. on TP2, so it's not working.
> > I went to the trouble shooting guide and I have 0.058 Vrms on pin 6 of
> > U11 with the RF probe.
> > Looking at the archives of the reflector that would indicate that U11
> > is bad and I need a replacement, correct? or are there other things I
> > should look at first?
> > The good thing is I'm becoming very accustomed to the radio and
> > enjoying the trouble shooting.
> > Thanks for all the help, I really appreciate it.
> >
> > 73,
> > Tom Bewick, K2BEW
> >
>
>

Neil Zampella

Re: K2 VCO Alignment T5 L30

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
trying to figure out the problem poring over the troubleshooting steps,
emails to Don, and magnified visual checks against the part location
diagrams. I never did see that error and sent the rig to Elecraft,
where it was noticed and replaced.

73,
Neil, KN3ILZ

On 1/22/2019 9:57 PM, K2bew wrote:

> 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 components again in that section with the RF board disconnected and
> out of the case.
> I found much to my chagrin I had not installed D37 and D38! I had them
> checked off in the manual as being installed, and I even wrote in pencil in
> the margin on the next step where you put the rest of the V149's in the RF
> board that I had 2 left over, but I failed to notice I had them left over
> because I did not put them in the step before!, good grief.
> Anyway I have a high BFO reading of 4917.60 and a low reading of 4911.98
> with a difference of 5.62.
> Thank you Don and to others that gave suggestions, and I do wish those
> having similar problems well in their trouble shooting.
>
> Upward and onward 73,
> Tom Bewick, K2BEW
>
>
> On Sun, Jan 20, 2019 at 8:22 AM Don Wilhelm <[hidden email]> wrote:
>
>> 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 1/19/2019 6:35 PM, K2bew wrote:
>>> 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 red wire of T5.
>>> That got me a voltage of 8.5V on R30 with L30 bottomed out that I
>>> was able to easily back off to a stable 6 volts.
>>> I went ahead and did the voltage tests on the other bands and had a
>>> nice range of 1.844 to 6 volts as my low and high on the VCO.
>>> So, that's all set.
>>>
>>> However, new problem. I went on to the test the BFO and I have 0000.04
>>> kHz. on TP2, so it's not working.
>>> I went to the trouble shooting guide and I have 0.058 Vrms on pin 6 of
>>> U11 with the RF probe.
>>> Looking at the archives of the reflector that would indicate that U11
>>> is bad and I need a replacement, correct? or are there other things I
>>> should look at first?
>>> The good thing is I'm becoming very accustomed to the radio and
>>> enjoying the trouble shooting.
>>> Thanks for all the help, I really appreciate it.
>>>
>>> 73,
>>> Tom Bewick, K2BEW
>>>
>>

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Jim KO5V

Re: K2 VCO Alignment T5 L30

In reply to this post by K2bew

Tom,

On my latest K2 build, I put a 1pf cap into the C68 (10pf) location. The 1pf cap was labelled "1D", which looked a lot like a "10" to my eyes. I think it took me about 4 hours to figure that one out. Once fixed, it all fell into place, and everything worked.

We all do it!

73, Jim KO5V

"Message: 3
Date: Tue, 22 Jan 2019 21:57:09 -0500
From: K2bew <[hidden email]>
To: [hidden email]
Cc: Elecraft Mail List <[hidden email]>
Subject: Re: [Elecraft] K2 VCO Alignment T5 L30
Message-ID:
<[hidden email]>
Content-Type: text/plain; charset="UTF-8"

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 components again in that section with the RF board disconnected and
out of the case.
I found much to my chagrin I had not installed D37 and D38! I had them
checked off in the manual as being installed, and I even wrote in pencil in
the margin on the next step where you put the rest of the V149's in the RF
board that I had 2 left over, but I failed to notice I had them left over
because I did not put them in the step before!, good grief.
Anyway I have a high BFO reading of 4917.60 and a low reading of 4911.98
with a difference of 5.62.
Thank you Don and to others that gave suggestions, and I do wish those
having similar problems well in their trouble shooting.

Upward and onward 73,
Tom Bewick, K2BEW"
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]