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K2 ..K2 100w ATU .. hirefl current error and then over current failure

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stephen pearce

K2 ..K2 100w ATU .. hirefl current error and then over current failure

Does anyone recognise this pattern ..
k2 100W
kat100 (rev b board)

..
apparently intermittent error ...
initially hirefl current error on auto tuning ...
then overcurrent failure of power supply when auto tuning at high current ...

rx working fine ... in kat100 ant1/ant2 relay seems to be ok .. as is
hi/low current relay
and all the L and C relays for the auto tuner seem to click in
appropriately when you run through them in the set up menu on the k2

I've inspected the board in the kat100 and there are no obvious dry or
loose solder joins ...

If you tune at sequentially higher power settings starting at 0.1,
then just under 10 (so as not to trigger the high power relay )
then just above 10w then 20+w .. then full power it seems to avoid the
over current failure of the supply ..

Why the supply (which is mfj4125) is cutting out (it must have a
resettable fuse as it recovers after about 30 sec) puzzles me ..
previously I have observed the k2 shut itself down before this happens
.. and makes me wonder if rf is getting into the supply ..
particularly if there is an initial significant mismatch in the atu
before it completes its auto tune

I have tried "init" reset in the k2 atu submenu .. as well as the cal
routines ...

tried transmitting into dummy load and into antenna ...neither seems
to make a consistant difference ...

possibly there is a fault in the fwd/refl power sensing in the atu ..
but this should not produce over current cut out in the supply

(this k2/kat100 is a friends ...I tried substuting my kat100 .. which
seems to work ok with his k2)

Any suggestions appreciated ...

73s
zl1any

--
Stephen Pearce
Critical Care
Whangarei
ph 021 390 997
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Don Wilhelm-4

Re: K2 ..K2 100w ATU .. hirefl current error and then over current failure

All quite logical - it seems you always have full power output (and then
some more too).
My best guess is that you have damaged the diodes D16 and D17 in the
KPA100, and you are always transmitting at full power - which may be far
in excess of 100 watts.

In other words, your KPA100 does not throttle back to 20 watts when
tuning, it tries to tune at full power - and too much of that can cause
burned relays in your KAT100.

The resettable fuse in the base K2 is also tripping due to high current
required by the base K2 PA transistors - stop trying to transmit until
you get those diodes fixed, you could cause further damage because
everything is running at "full tilt".

Do you have an external wattmeter and a dummy load around somewhere? If
so, connect them to the KPA100 (no KAT100) and set the K2 power at 3 to
5 watts (use 40 meters). Do a TUNE and observe the power indicated on
the external wattmeter. If it is above 12 watts, then you have
something not working in the KPA100 wattmeter, and damaged diodes is the
most likely cause.

If you are not in the habit of removing the antenna from the K2 when not
in use, know that it only takes a nearby lightning stroke to stress
those diodes, and they are also susceptible to damage from rain static,
wind static and snow static. Get a DC discharge path across all your
antennas to help, but disconnect the antennas when not in use is your
best insurance.

73,
Don W3FPR

On 1/12/2012 3:49 AM, stephen pearce wrote:

> Does anyone recognise this pattern ..
> k2 100W
> kat100 (rev b board)
>
> ..
> apparently intermittent error ...
> initially hirefl current error on auto tuning ...
> then overcurrent failure of power supply when auto tuning at high current ...
>
> rx working fine ... in kat100 ant1/ant2 relay seems to be ok .. as is
> hi/low current relay
> and all the L and C relays for the auto tuner seem to click in
> appropriately when you run through them in the set up menu on the k2
>
> I've inspected the board in the kat100 and there are no obvious dry or
> loose solder joins ...
>
> If you tune at sequentially higher power settings starting at 0.1,
> then just under 10 (so as not to trigger the high power relay )
> then just above 10w then 20+w .. then full power it seems to avoid the
> over current failure of the supply ..
>
> Why the supply (which is mfj4125) is cutting out (it must have a
> resettable fuse as it recovers after about 30 sec) puzzles me ..
> previously I have observed the k2 shut itself down before this happens
> .. and makes me wonder if rf is getting into the supply ..
> particularly if there is an initial significant mismatch in the atu
> before it completes its auto tune
>
> I have tried "init" reset in the k2 atu submenu .. as well as the cal
> routines ...
>
> tried transmitting into dummy load and into antenna ...neither seems
> to make a consistant difference ...
>
> possibly there is a fault in the fwd/refl power sensing in the atu ..
> but this should not produce over current cut out in the supply
>
> (this k2/kat100 is a friends ...I tried substuting my kat100 .. which
> seems to work ok with his k2)
>
>
> Any suggestions appreciated ...
>
> 73s
> zl1any
>
>

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Nidge_(G0NIG)

K2: Intermittent fault on 15m and 12m.

Hi All

Once in a while I have an issue with my K2 on 15m and 12m in that
there is no receive and, according to the internal power metering,
next to no transmit. As I say this is intermittent.

The radio is currently in it's QRP format with an internal battery fitted.
However this issue crops up even when the supply is external and the
KPA100 is installed. I could probably understand it if it was on 17m
and 15m or 12m and 10m as the bandpass filters and relays are shared
but, and maybe I haven't looked hard enough, I can't see the link between
15m and 12m.

Any thoughts and advice much appreciated.

Regards

Nidge (G0NIG)

IO93dv
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Don Wilhelm-4

Re: K2: Intermittent fault on 15m and 12m.

Nidge,

There is one link between 15 and 12 meters, and that is relay K6 which
should be set on both bands.
Those are latching relays, so you can set to the band, power down and
check the continuity at the relay pins.

73,
Don W3FPR

On 1/12/2012 8:04 AM, Nigel (Nidge) Smith wrote:

>
> Hi All
>
> Once in a while I have an issue with my K2 on 15m and 12m in that
> there is no receive and, according to the internal power metering,
> next to no transmit. As I say this is intermittent.
>
> The radio is currently in it's QRP format with an internal battery fitted.
> However this issue crops up even when the supply is external and the
> KPA100 is installed. I could probably understand it if it was on 17m
> and 15m or 12m and 10m as the bandpass filters and relays are shared
> but, and maybe I haven't looked hard enough, I can't see the link between
> 15m and 12m.
>
>

Nidge_(G0NIG)

Re: K2: Intermittent fault on 15m and 12m.

Once again Don you're there to the rescue.

Thanks very much for the very quick response.

We have a saying over here when one doesn't see
the obvious and that is I "Should have gone to Specsavers".

The bottom will be coming off shortly and a check done

Once again thank you.

Regards

Nidge (G0NIG)

IO93dv

--------------------------------------------------
From: "Don Wilhelm" <[hidden email]>
Sent: Thursday, January 12, 2012 1:18 PM
To: "Nigel (Nidge) Smith" <[hidden email]>
Cc: <[hidden email]>
Subject: Re: [Elecraft] K2: Intermittent fault on 15m and 12m.

> Nidge,
>
> There is one link between 15 and 12 meters, and that is relay K6 which
> should be set on both bands.
> Those are latching relays, so you can set to the band, power down and
> check the continuity at the relay pins.
>
> 73,
> Don W3FPR
>
> On 1/12/2012 8:04 AM, Nigel (Nidge) Smith wrote:
>>
>> Hi All
>>
>> Once in a while I have an issue with my K2 on 15m and 12m in that
>> there is no receive and, according to the internal power metering,
>> next to no transmit. As I say this is intermittent.
>>
>> The radio is currently in it's QRP format with an internal battery
>> fitted.
>> However this issue crops up even when the supply is external and the
>> KPA100 is installed. I could probably understand it if it was on 17m
>> and 15m or 12m and 10m as the bandpass filters and relays are shared
>> but, and maybe I haven't looked hard enough, I can't see the link between
>> 15m and 12m.
>>
>>