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K1 TX output low on 2 of 4 bands

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David Ek-2

K1 TX output low on 2 of 4 bands

My K1 (#1066, built 11 years ago) is a four-bander with ATU and internal
battery pack. In May I built an Elecraft W1 wattmeter and used it to
discover that my TX output (When "Out" in the menu is set to 7.0W) is
only 1.2W on 15 meters. At that time, all other bands showed an output
of 5W.

However, last night, after an afternoon of using my K1 while fruitlessly
trying to tune up a new antenna, I noticed that the output on 20 meters
was also now down, measuring 1.5W. I strongly suspect that a component
failed due to TX'ing into high SWR while trying to adjust the antenna I
was working on. 40 and 30 meters still seem to be okay. (My guess is
that 15 is low for the same reason--I just didn't discover it in a
timely fashion like I did with 20 meters).

So, anybody have a suggestion for where to start with troubleshooting?
Should I suspect the filter board? Any components in particular?

Thanks in advance for any morsels of wisdom -

Dave NK0E
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David Ek-2

Re: K1 TX output low on 2 of 4 bands

Never mind. It was operator error. Helps to read the instructions.
Self-administering dope slap now...

73, Dave NK0E

On 7/5/2013 7:55 AM, David Ek wrote:

> My K1 (#1066, built 11 years ago) is a four-bander with ATU and
> internal battery pack. In May I built an Elecraft W1 wattmeter and
> used it to discover that my TX output (When "Out" in the menu is set
> to 7.0W) is only 1.2W on 15 meters. At that time, all other bands
> showed an output of 5W.
>
> However, last night, after an afternoon of using my K1 while
> fruitlessly trying to tune up a new antenna, I noticed that the output
> on 20 meters was also now down, measuring 1.5W. I strongly suspect
> that a component failed due to TX'ing into high SWR while trying to
> adjust the antenna I was working on. 40 and 30 meters still seem to be
> okay. (My guess is that 15 is low for the same reason--I just didn't
> discover it in a timely fashion like I did with 20 meters).
>
> So, anybody have a suggestion for where to start with troubleshooting?
> Should I suspect the filter board? Any components in particular?
>
> Thanks in advance for any morsels of wisdom -
>
> Dave NK0E
> ______________________________________________________________
> 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

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Mike Morrow-3

Re: K1 TX output low on 2 of 4 bands

In reply to this post by David Ek-2

Dave/NK0E wrote:

> My K1 (#1066, built 11 years ago) is a four-bander with ATU and internal
> battery pack.

What power supply were you using when you measured the output power
that you report below?

> In May I built an Elecraft W1 wattmeter and used it to discover that my
> TX output (When "Out" in the menu is set to 7.0W) is only 1.2W on 15
> meters. At that time, all other bands showed an output of 5W.
>
> However, last night, after an afternoon of using my K1 while fruitlessly
> trying to tune up a new antenna, I noticed that the output on 20 meters
> was also now down, measuring 1.5W.

> I strongly suspect that a component failed due to TX'ing into high
> SWR while trying to adjust the antenna I was working on.

This is extremely unlikely. Any RF board component failure would affect
all four bands, not just 20m and 15m. During use of a very poor antenna
load, the most common result is shorting of the RF board D19 Zener that
is across the RF-Q7 PA transistor, which is what D19 is designed to do to
protect RF-Q7 (and usually destroy itself in the process). This definitely
has NOT happened to your K1. Rest assured then that nothing was hurt
on your K1 during your antenna tuning efforts.

When some bands still function well, but others do not, it is a certainty
that the problem is on the filter board.

You have an older K1, and possibly an early KFL1-4 filter board. The
16 trimmer capacitors that are on the KFL1-4 were originally white-body
capacitors that were very prone to spontaneously changing their effective
value. A couple of years after the KFL1-4 was introduced, Elecraft changed
all 16 trimmers to a much more stable design with a light blue body.

Look at the four rows of trimmer capacitors on your KFL1-4, which are
easily observed from the back of the K1 even without removing the KAT1.
If they they do not have light blue plastic bodies, then you have the
old troublesome original trimmers in place. You'll need to get the
replacement trimmers and install them. Those are almost certainly
the source of your problems.

OTOH, if you have the newer blue-body trimmers, you will still want
to re-align your KFL1-4 to restore full output. In fact, you'll
want to do that if you have white trimmers, just to verify that
output can be restored in the interim before change out.

When I still had those old trimmers on mine, I needed to re-peak 15m
and 20m on my KFL1-4 every few months due to the drop in output power
I observed. So did a lot of other people. After such results, Elecraft
supplied a set of 16 blue-body replacements. It was *not* a lot of fun
removing 16 trimmers and replacing them, but it was worth it. I
recently re-peaked my KFL1-4 after more than eight years since last
performed, and found essentially no pre-peaking degradation.

73,
Mike / KK5F
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David Ek-2

Re: K1 TX output low on 2 of 4 bands

Mike, I didn't have the K1 internal ATU switched out like I thought I
did. All is well (except for my embarrassment...).

73, Dave NK0E

On 7/5/2013 8:57 AM, Mike Morrow wrote:

> Dave/NK0E wrote:
>
>> My K1 (#1066, built 11 years ago) is a four-bander with ATU and internal
>> battery pack.
> What power supply were you using when you measured the output power
> that you report below?
>
>> In May I built an Elecraft W1 wattmeter and used it to discover that my
>> TX output (When "Out" in the menu is set to 7.0W) is only 1.2W on 15
>> meters. At that time, all other bands showed an output of 5W.
>>
>> However, last night, after an afternoon of using my K1 while fruitlessly
>> trying to tune up a new antenna, I noticed that the output on 20 meters
>> was also now down, measuring 1.5W.
>> I strongly suspect that a component failed due to TX'ing into high
>> SWR while trying to adjust the antenna I was working on.
> This is extremely unlikely. Any RF board component failure would affect
> all four bands, not just 20m and 15m. During use of a very poor antenna
> load, the most common result is shorting of the RF board D19 Zener that
> is across the RF-Q7 PA transistor, which is what D19 is designed to do to
> protect RF-Q7 (and usually destroy itself in the process). This definitely
> has NOT happened to your K1. Rest assured then that nothing was hurt
> on your K1 during your antenna tuning efforts.
>
> When some bands still function well, but others do not, it is a certainty
> that the problem is on the filter board.
>
> You have an older K1, and possibly an early KFL1-4 filter board. The
> 16 trimmer capacitors that are on the KFL1-4 were originally white-body
> capacitors that were very prone to spontaneously changing their effective
> value. A couple of years after the KFL1-4 was introduced, Elecraft changed
> all 16 trimmers to a much more stable design with a light blue body.
>
> Look at the four rows of trimmer capacitors on your KFL1-4, which are
> easily observed from the back of the K1 even without removing the KAT1.
> If they they do not have light blue plastic bodies, then you have the
> old troublesome original trimmers in place. You'll need to get the
> replacement trimmers and install them. Those are almost certainly
> the source of your problems.
>
> OTOH, if you have the newer blue-body trimmers, you will still want
> to re-align your KFL1-4 to restore full output. In fact, you'll
> want to do that if you have white trimmers, just to verify that
> output can be restored in the interim before change out.
>
> When I still had those old trimmers on mine, I needed to re-peak 15m
> and 20m on my KFL1-4 every few months due to the drop in output power
> I observed. So did a lot of other people. After such results, Elecraft
> supplied a set of 16 blue-body replacements. It was *not* a lot of fun
> removing 16 trimmers and replacing them, but it was worth it. I
> recently re-peaked my KFL1-4 after more than eight years since last
> performed, and found essentially no pre-peaking degradation.
>
> 73,
> Mike / KK5F