K2 - intermittent probem in RX and TX

[oe9fwv]

I have an intermittent problem when receiving and transmitting.
Rx: the received modulation from other stations on 80/40m in LSB sounds like it is on the
wrong sideband. The RX level seems quite low. Sometimes I have the impression that the
frequency is not stable, it is like the radio is tuning upwards, the sound of the signal becomes
narrower (with the OP1 selected)
Tx: there is no or very little output power.
All symptoms disappear when I tap on the top case and the radio works normal for a while
until it appears again.

Can someone imagine where I should start looking for the problem?
Any specific information on the installed options needed?

73!
Werner oe9fwv

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[Don Wilhelm-4]

Werner,

Look in the BFO and VFO areas.

An problem that corrects itself by tapping is normally caused by a bad
solder connection.
Reflow the soldering (adding a little bit of flux from new solder) with
a hot (400 degC) iron.

73,
Don W3FPR

On 4/8/2012 6:48 AM, Dr. Werner Furlan wrote:

> I have an intermittent problem when receiving and transmitting.
> Rx: the received modulation from other stations on 80/40m in LSB sounds like it is on the
> wrong sideband. The RX level seems quite low. Sometimes I have the impression that the
> frequency is not stable, it is like the radio is tuning upwards, the sound of the signal becomes
> narrower (with the OP1 selected)
> Tx: there is no or very little output power.
> All symptoms disappear when I tap on the top case and the radio works normal for a while
> until it appears again.
>
> Can someone imagine where I should start looking for the problem?
> Any specific information on the installed options needed?
>
> 73!
> Werner oe9fwv
>

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[oe9fwv]

hi Don,

I treated the region around TP1 with cold spray and had the impression that the problem appeared there.
I soldered all junctions in this region with the result that the problem is now permanent, which should make troubleshooting somehow easier.
The symptoms are:
when I listen to a signal, it sounds like when you listen to SSB on the wrong sideband (it is not understandable)
when I transmit, there is no output power, and the power indicator on the display shows 0.4, no matter what I choose with the power knob.
I tried to run CAL PLL, but it did not change anything :-(

73!
Werner oe9fwv

[oe9fwv]

found it!

it was a bare lead of L33, which slightly touched a nearby solder point.
I bent it towards the toroid, as far away from any solder point and now everything sounds good again.
Thank you Don, you pointed me in the correct direction.

73!
Werner oe9fwv

[Don Wilhelm-4]

Werner,

Glad to hear you found it.  Have a good week.

73,
Don W3FPR

On 4/8/2012 6:52 PM, oe9fwv wrote:

> found it!
>
> it was a bare lead of L33, which slightly touched a nearby solder point.
> I bent it towards the toroid, as far away from any solder point and now
> everything sounds good again.
> Thank you Don, you pointed me in the correct direction.
>
> 73!
> Werner oe9fwv
>
>

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[oe9fwv]

thank you Don,

When I tested the K2 on all bands, I found there is still a problem left.
output power on 40 and 80m is only 5 or 6 W max.
The power display on the K2 shows up to 15 W, but on my accurate LP100 meter there is only 6 W out.
Output on 1.8, 10-28 Mhz is normal.
I think this has come up since I corrected the problem with the L33 lead.

Do I need any readjustment?

TIA, Werner OE9FWV

[Don Wilhelm-4]

Werner,

Is that with the base K2 (no KAT2, no KPA100 and no KAT100)?
If so, is the K2 operating into a 50 ohm load?  With the bare base K2,
the RF detector must see a 50 ohm non-reactive load to have good power
indication.

The KAT2 or KAT100 or KPA100 have real wattmeters which fix that condition.

73,
Don W3FPR

On 4/9/2012 5:17 AM, oe9fwv wrote:

> thank you Don,
>
> When I tested the K2 on all bands, I found there is still a problem left.
> output power on 40 and 80m is only 5 or 6 W max.
> The power display on the K2 shows up to 15 W, but on my accurate LP100 meter
> there is only 6 W out.
> Output on 1.8, 10-28 Mhz is normal.
> I think this has come up since I corrected the problem with the L33 lead.
>
> Do I need any readjustment?
>
> TIA, Werner OE9FWV
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/K2-intermittent-probem-in-RX-and-TX-tp7447445p7449218.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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[oe9fwv]

hi Don,

yes it is with the base K2, and yes I sent into a dummy load.
I'll repeat the test with a better setup (no switch between dummy load and K2/Wattmeter)
But the fact that only 80 and 40m is affected lets me suspect the issue is with the K2.

tnx a lot for your support!

Werner oe9fwv


On 9 Apr 2012 at 9:56, Don Wilhelm wrote:

>
> Is that with the base K2 (no KAT2, no KPA100 and no KAT100)?
> If so, is the K2 operating into a 50 ohm load?  With the bare base K2,
> the RF detector must see a 50 ohm non-reactive load to have good power
> indication.
>
> The KAT2 or KAT100 or KPA100 have real wattmeters which fix that
> condition.
>
> 73,
> Don W3FPR

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[oe9fwv]

I have repeated my output tests with a known good dummy load and cables.
Results are different now.
I have around 10-12W on all bands except 12m - where it is only 5 Watts, which are also displayed correctly.
Is this normal? I am very rarely activ on 12m maybe this has always been like this and I did not take notice.

73!
Werner oe9fwv

[Don Wilhelm-4]

Werner,

My suspicion is that it has been like that a long time.  You may want to
set the power knob back to about 2 watts, set the band to 12 meters and
then do a TUNE - peak the bandpass filter - trimmers C44 and C46.
After peaking those capacitors, test the maximum output again on 12 meters.

73,
Don W3FPR

On 4/9/2012 1:20 PM, oe9fwv wrote:

> I have repeated my output tests with a known good dummy load and cables.
> Results are different now.
> I have around 10-12W on all bands except 12m - where it is only 5 Watts,
> which are also displayed correctly.
> Is this normal? I am very rarely activ on 12m maybe this has always been
> like this and I did not take notice.
>
> 73!
> Werner oe9fwv
>

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