K2 Won't power on

[JeremyJones]

With the tuner disconnected, I'm still getting 600mV at the base of Q8 while doing a tune.  The display on the radio shows power of 0.3.

[Don Wilhelm-4]

Jeremy,

A power reading of 0.1, 0.2 or 0.3 is only residual noise on the power
detection circuits.  Since you do not have Q7 and Q8 installed, your
real power output is zero.

Yes, go ahead and change Q11 and Q13.  That is not certain to change
anything, but it will do no harm.
A slightly lower than normal bias voltage for the PA transistors is not
a problem, but if it is higher than 0.64 volts, that is a problem that
should warn you not to install Q7 and Q8 until it is resolved.

73,
Don W3FPR

On 2/17/2014 7:34 PM, JeremyJones wrote:
> With the tuner disconnected, I'm still getting 600mV at the base of Q8 while
> doing a tune.  The display on the radio shows power of 0.3.
>
>

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[ab2tc]

Hi Don,

I always use Nabble to reply to postings. Do you not see the response to Jeremy below and then the rest is <snip>ped off?

AB2TC - Knut

Don Wilhelm-4 wrote

Jeremy,

Remove the tuner and you will not be bothered with the LowP messages.
In fact when testing the base K2, you should remove the tuner and
operate the basic K2 into a dummy load.

Where are you measuring 600mV?  That is one problem with replying using
Nabble, it strips off what you are relying to and only Nabble users can
make sense of things.  I choose to download directly from the Elecraft
list as email, so some hint of the history is helpful.

73,
Don W3FPR
<snip>

[Don Wilhelm-4]

Knut,

Yes, that made it through OK.  I usually see posts through Nabble that
contain no reference information, and sometimes the subject line is not
relevant.
I was blaming the way Nabble works, but I guess that is not the issue.  
Apparently the poster has a choice of leaving a bit of reference or not
- I wish more would give some of that bit of history.

73,
Don W3FPR

On 2/18/2014 1:55 PM, ab2tc wrote:
> Hi Don,
>
> I always use Nabble to reply to postings. Do you not see the response to
> Jeremy below and then the rest is <snip>ped off?
>
> AB2TC - Knut
>
>
>

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[JeremyJones]

I don't know how much over 0.64 volts is bad, but I am getting 0.656.

I didn't realize that a web reply was cutting off what I was replying to.  I always hit the reply button and assumed it included the original text.

Jeremy

Don Wilhelm-4 wrote

Jeremy,

A power reading of 0.1, 0.2 or 0.3 is only residual noise on the power
detection circuits.  Since you do not have Q7 and Q8 installed, your
real power output is zero.

Yes, go ahead and change Q11 and Q13.  That is not certain to change
anything, but it will do no harm.
A slightly lower than normal bias voltage for the PA transistors is not
a problem, but if it is higher than 0.64 volts, that is a problem that
should warn you not to install Q7 and Q8 until it is resolved.

73,
Don W3FPR

[Don Wilhelm-4]

Jeremy,

Make a quick check on your voltmeter - measure a new Alkaline battery,
you should see quite close to 1.50 volts.

Are you making the measurement by using TUNE?  If not, you should be.

Is this an older K2 with a trimpot at R60?  If so, it should be turned
fully counterclockwise.
Check the resistors R59 through R63 to be certain they are the correct
values.

I would be puzzled about a bias voltage higher than 0.64 volts because
it could lead to higher current and the resulting heat dissipation in
the PA transistors.

Thank you for adding a bit of the prior post that you are responding to
- it helps a lot.

73,
Don W3FPR

On 2/18/2014 4:46 PM, JeremyJones wrote:
> I don't know how much over 0.64 volts is bad, but I am getting 0.656.
>
> I didn't realize that a web reply was cutting off what I was replying to.  I
> always hit the reply button and assumed it included the original text.
>

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[JeremyJones]

A new AA battery right from the package is giving me 1.615V on the fluke meter.  This is a newer K2 (#7405).  I had some issues when building it which caused me to go through a couple of sets of PA finals before I had to send it to you to get sorted out.  It was working great until now, so hopefully there isn't something residual that is creeping up now.  The resistor values are all correct according to the manual.
R59 4.7k
R60 100
R61 120
R62 2.7k
R63 220

I am performing the voltage measurement on the Base pad of where Q8 would go, and pressing and holding the "Tune" button on the front of the radio.

Jeremy

Don Wilhelm-4 wrote

Jeremy,

Make a quick check on your voltmeter - measure a new Alkaline battery,
you should see quite close to 1.50 volts.

Are you making the measurement by using TUNE?  If not, you should be.

Is this an older K2 with a trimpot at R60?  If so, it should be turned
fully counterclockwise.
Check the resistors R59 through R63 to be certain they are the correct
values.

I would be puzzled about a bias voltage higher than 0.64 volts because
it could lead to higher current and the resulting heat dissipation in
the PA transistors.

Thank you for adding a bit of the prior post that you are responding to
- it helps a lot.

73,
Don W3FPR

On 2/18/2014 4:46 PM, JeremyJones wrote:
> I don't know how much over 0.64 volts is bad, but I am getting 0.656.
>
> I didn't realize that a web reply was cutting off what I was replying to.  I
> always hit the reply button and assumed it included the original text.
>

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Home: http://mailman.qth.net/mailman/listinfo/elecraft
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[Don Wilhelm-4]

Jeremy,

That voltage is close to what I would expect from a new Lithium battery.
If you are measuring an Alkaline battery, then your voltmeter is a bit
on the high side.

So if Alkaline battery, then your 0.65 measurement is likely OK, but if
that battery is a Lithium type, the bias is a bit high and you may have
to experiment with slightly different values at R60 to bring the bias
voltage down a bit.

73,
Don W3FPR

On 2/18/2014 6:58 PM, JeremyJones wrote:

> A new AA battery right from the package is giving me 1.615V on the fluke
> meter.  This is a newer K2 (#7405).  I had some issues when building it
> which caused me to go through a couple of sets of PA finals before I had to
> send it to you to get sorted out.  It was working great until now, so
> hopefully there isn't something residual that is creeping up now.  The
> resistor values are all correct according to the manual.
> R59 4.7k
> R60 100
> R61 120
> R62 2.7k
> R63 220
>
> I am performing the voltage measurement on the Base pad of where Q8 would
> go, and pressing and holding the "Tune" button on the front of the radio.
>
>

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[JeremyJones]

Yes that was an Alkaline battery.  That makes me feel better about installing the new finals once they arrive.  In the mean time I have a KAT100 and KPA100 to build.

Jeremy

Don Wilhelm-4 wrote

Jeremy,

That voltage is close to what I would expect from a new Lithium battery.
If you are measuring an Alkaline battery, then your voltmeter is a bit
on the high side.

So if Alkaline battery, then your 0.65 measurement is likely OK, but if
that battery is a Lithium type, the bias is a bit high and you may have
to experiment with slightly different values at R60 to bring the bias
voltage down a bit.

73,
Don W3FPR

On 2/18/2014 6:58 PM, JeremyJones wrote:
> A new AA battery right from the package is giving me 1.615V on the fluke
> meter.  This is a newer K2 (#7405).  I had some issues when building it
> which caused me to go through a couple of sets of PA finals before I had to
> send it to you to get sorted out.  It was working great until now, so
> hopefully there isn't something residual that is creeping up now.  The
> resistor values are all correct according to the manual.
> R59 4.7k
> R60 100
> R61 120
> R62 2.7k
> R63 220
>
> I am performing the voltage measurement on the Base pad of where Q8 would
> go, and pressing and holding the "Tune" button on the front of the radio.
>
>

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[JeremyJones]

Q7, Q8, Q11 and Q13 are all now replaced, and everything seems to be working normally again.  Thanks everyone for all the help.

73,
Jeremy
VA3ZTF

JeremyJones wrote

Yes that was an Alkaline battery.  That makes me feel better about installing the new finals once they arrive.  In the mean time I have a KAT100 and KPA100 to build.

Jeremy