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Ailing K2

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W4TZM

Ailing K2

I sent this to Elecraft support, but I thought I'd post it here too to see
if the collective wisdom of the group might have anything to add.

Tonight during dinner I noticed my K2/100 (w/ KAT100) was showing no noise
on the S Meter. I unplugged the headphones and could hear no signals at
all, as if the antenna was disconnected. If I tried to tune, the ATU would
light up (sometimes) and it would run a tuning cycle, but I don't know if
it was finding a match. No noise at all on the bands.

I started taking the panels off and the next disconcerting bit was when
bits of plastic started falling out. Q11 and Q8 are both split in half
with most of the body of Q11 loose in the chassis and the base side of Q8
split from the collector & emitter.

I had left my radio on this afternoon while I was a few doors up the hill
working and we had a short thunderstorm. There were no close strikes (very
little lightning at all) but yeah, I should have disconnected things but
didn't realize I had left it in that state. A visual inspection doesn't
show anything else obviously wrong aside from some slight scorch mark where
Q11 went boom. No traces look blown and there are no signs that any of the
caps or resistors in that area are damaged.

Aside from Q11 & Q8, are there other likely candidates for replacement or
places to check? The ATU & PA100 pass a visual inspection. The storm is a
pretty strong correlation, but are there any other likely scenarios that
could cause this failure?

Thanks,

Tommy
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N0AZZ

Re: Ailing K2

Tommy

Lighting is one of those things that keeps on giving in many ways as far as
the electronic components in your radio. You may be able to replace XYZ
items and it fixes the problem for now, it's the thing's that it weakens
that all do not show up at the same time but continue to fail. That is the
reason why so many insurance company's choose to replace the unit instead of
repair, the same is true for radio repair shops. These "can be" an ongoing
issue that keeps on giving for some time. YMMV This is worth just what you
paid for it 8>)

73,
Fred/N0AZZ
K3 Ser #'s 6730/5299--KX3 # 2573--K2/100--KAT100
P3/SVGA--KPA500--KAT500--W2

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Tommy Mitchell
Sent: Wednesday, April 17, 2013 7:58 PM
To: [hidden email]
Subject: [Elecraft] Ailing K2

I sent this to Elecraft support, but I thought I'd post it here too to see
if the collective wisdom of the group might have anything to add.

Tonight during dinner I noticed my K2/100 (w/ KAT100) was showing no noise
on the S Meter. I unplugged the headphones and could hear no signals at
all, as if the antenna was disconnected. If I tried to tune, the ATU would
light up (sometimes) and it would run a tuning cycle, but I don't know if it
was finding a match. No noise at all on the bands.

I started taking the panels off and the next disconcerting bit was when bits
of plastic started falling out. Q11 and Q8 are both split in half with most
of the body of Q11 loose in the chassis and the base side of Q8 split from
the collector & emitter.

I had left my radio on this afternoon while I was a few doors up the hill
working and we had a short thunderstorm. There were no close strikes (very
little lightning at all) but yeah, I should have disconnected things but
didn't realize I had left it in that state. A visual inspection doesn't
show anything else obviously wrong aside from some slight scorch mark where
Q11 went boom. No traces look blown and there are no signs that any of the
caps or resistors in that area are damaged.

Aside from Q11 & Q8, are there other likely candidates for replacement or
places to check? The ATU & PA100 pass a visual inspection. The storm is a
pretty strong correlation, but are there any other likely scenarios that
could cause this failure?

Thanks,

Tommy
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-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2013.0.2904 / Virus Database: 3162/6252 - Release Date: 04/17/13

-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2013.0.2904 / Virus Database: 3162/6252 - Release Date: 04/17/13

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Andy McMullin

Re: Ailing K2

In reply to this post by W4TZM

Yup,

When I worked for Sperry Univac we used to call that "reducing the mean
time between failure". Not just lightning though, not following anti-static
precautions can have the same effects. The kit doesn't last in working
condition for as long as it should do.

Cheers

Andy, G8TQH

----------------------------------------
From: "Fred Smith" <[hidden email]>
Sent: 18 April 2013 10:07
To: "Tommy Mitchell" <[hidden email]>, [hidden email]
Subject: Re: [Elecraft] Ailing K2

Tommy

Lighting is one of those things that keeps on giving in many ways as far
as
the electronic components in your radio. You may be able to replace XYZ
items and it fixes the problem for now, it's the thing's that it weakens
that all do not show up at the same time but continue to fail. That is the
reason why so many insurance company's choose to replace the unit instead
of
repair, the same is true for radio repair shops. These "can be" an ongoing
issue that keeps on giving for some time. YMMV This is worth just what you
paid for it 8>)

73,
Fred/N0AZZ
K3 Ser #'s 6730/5299--KX3 # 2573--K2/100--KAT100
P3/SVGA--KPA500--KAT500--W2

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Tommy Mitchell
Sent: Wednesday, April 17, 2013 7:58 PM
To: [hidden email]
Subject: [Elecraft] Ailing K2

I sent this to Elecraft support, but I thought I'd post it here too to see
if the collective wisdom of the group might have anything to add.

Tonight during dinner I noticed my K2/100 (w/ KAT100) was showing no noise
on the S Meter. I unplugged the headphones and could hear no signals at
all, as if the antenna was disconnected. If I tried to tune, the ATU
would
light up (sometimes) and it would run a tuning cycle, but I don't know if
it
was finding a match. No noise at all on the bands.

I started taking the panels off and the next disconcerting bit was when
bits
of plastic started falling out. Q11 and Q8 are both split in half with
most
of the body of Q11 loose in the chassis and the base side of Q8 split from
the collector & emitter.

I had left my radio on this afternoon while I was a few doors up the hill
working and we had a short thunderstorm. There were no close strikes
(very
little lightning at all) but yeah, I should have disconnected things but
didn't realize I had left it in that state. A visual inspection doesn't
show anything else obviously wrong aside from some slight scorch mark
where
Q11 went boom. No traces look blown and there are no signs that any of
the
caps or resistors in that area are damaged.

Aside from Q11 & Q8, are there other likely candidates for replacement or
places to check? The ATU & PA100 pass a visual inspection. The storm is
a
pretty strong correlation, but are there any other likely scenarios that
could cause this failure?

Thanks,

Tommy
______________________________________________________________
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

-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2013.0.2904 / Virus Database: 3162/6252 - Release Date: 04/17/13

-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2013.0.2904 / Virus Database: 3162/6252 - Release Date: 04/17/13

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

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Don Wilhelm-4

Re: Ailing K2

In reply to this post by W4TZM

Tommy,

You are going to need a K2PAKIT from Elecraft. That kit includes a
matched set of PA transistors (replace both) as well as replacements for
Q11 and Q13 (also replace both). After you install Q11 and Q13, but
before you install Q7 and Q8, check the voltage on the base solder pads
for Q7 and Q8 during a TUNE - it should be no higher than 0.64 volts and
no lower than 0.61 volts. If it is not in range, find the cause and fix
that first so you do not zap the new PA transistors.

In addition to the PA transistors, check diodes D16 and D17 in the
KPA100 wattmeter and also diodes D1 and D2 in the KAT100 wattmeter and
replace them if there is any question about their health. You might
want to order 4 1N5711 diodes (Elecraft PN E560004) and arbitrarily
replace them.

What normally happens with a static surge on the antennas is that the
wattmeter diodes fail, and that causes the K2 to not sense the power
output - the MCU in the base K2, thinking there is no power output,
cranks up the drive to maximum possible, and that stresses the PA in the
base K2.

Good prevention is to add a DC path across all your feedlines (a high
value resistor - 5k to 50k will do or a 100 uHy choke of sufficient
current capacity) to bleed off static charge and arrange any antenna
switch to connect your K2 to a dummy load when not in use. You can get
static buildup on an antenna with no DC path across the feedline without
lightning - wind, rain, or snow can also cause a significant static
charge to build on the antenna.

73,
Don W3FPR

On 4/17/2013 8:58 PM, Tommy Mitchell wrote:

> I sent this to Elecraft support, but I thought I'd post it here too to see
> if the collective wisdom of the group might have anything to add.
>
> Tonight during dinner I noticed my K2/100 (w/ KAT100) was showing no noise
> on the S Meter. I unplugged the headphones and could hear no signals at
> all, as if the antenna was disconnected. If I tried to tune, the ATU would
> light up (sometimes) and it would run a tuning cycle, but I don't know if
> it was finding a match. No noise at all on the bands.
>
> I started taking the panels off and the next disconcerting bit was when
> bits of plastic started falling out. Q11 and Q8 are both split in half
> with most of the body of Q11 loose in the chassis and the base side of Q8
> split from the collector & emitter.
>
> I had left my radio on this afternoon while I was a few doors up the hill
> working and we had a short thunderstorm. There were no close strikes (very
> little lightning at all) but yeah, I should have disconnected things but
> didn't realize I had left it in that state. A visual inspection doesn't
> show anything else obviously wrong aside from some slight scorch mark where
> Q11 went boom. No traces look blown and there are no signs that any of the
> caps or resistors in that area are damaged.
>
> Aside from Q11 & Q8, are there other likely candidates for replacement or
> places to check? The ATU & PA100 pass a visual inspection. The storm is a
> pretty strong correlation, but are there any other likely scenarios that
> could cause this failure?
>
>

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Greg Troxel

Re: Ailing K2

Don Wilhelm <[hidden email]> writes:

> What normally happens with a static surge on the antennas is that the
> wattmeter diodes fail, and that causes the K2 to not sense the power
> output - the MCU in the base K2, thinking there is no power output,
> cranks up the drive to maximum possible, and that stresses the PA in
> the base K2.

Maybe this is too complicated, but perhaps the MCU could check for there
being a reasonable partial derivative from drive to perceived output,
and if not decline to increase drive, so that the secondary finals
damage could be avoided?
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Don Wilhelm-4

Re: Ailing K2

There is another mechanism in the MCU that helps do that, but it is not
always effective - that is the CAL CUR setting.
It must be set to 3.50 Amps for a K2 with a KPA100, and often the K2
will show HiCurr when the wattmeter diodes fail.
The problem I see with that is many users continue to operate in spite
of that warning. The situation gets worse if the user turns the power
knob to maximum. I recommend that the power knob be set to no more than
10 watts for the base K2 and no more than 100 watts with the KPA100.
Your signal will be cleaner on the bands and the power control will be
smoother.
If you "do the math", you will find only a miniscule difference between
100 watts and 120 watts at the receiving end. So why stress your
equipment by squeezing that last ounce of power out if it. I know,
historically hams have tried to get all they can out of a device, and
may not think of the stresses involved in that process.

There is another thing to watch to keep your Elecraft K2 or K3 or KX3
transceiver running with less stress, and that is to keep the power
supply voltage up. There is less stress on the components when using a
14.4 volt power source than when running at 12 volts. Your signal IMD
will be better with the increased voltage as well. The reason is that
the K2, K3, and KX3 attempt to maintain the requested power - for any
given power level, if the voltage is increased, the current will be
reduced. It is typically current that kills solid state devices in any
proper design.

73,
Don W3FPR

On 4/18/2013 8:42 AM, Greg Troxel wrote:

> Don Wilhelm <[hidden email]> writes:
>
>> What normally happens with a static surge on the antennas is that the
>> wattmeter diodes fail, and that causes the K2 to not sense the power
>> output - the MCU in the base K2, thinking there is no power output,
>> cranks up the drive to maximum possible, and that stresses the PA in
>> the base K2.
> Maybe this is too complicated, but perhaps the MCU could check for there
> being a reasonable partial derivative from drive to perceived output,
> and if not decline to increase drive, so that the secondary finals
> damage could be avoided?
>