K2 - KPA100 to much output on 80/40 m in SSB with Comp on

[oe9fwv]

hello to the group,

since the beginning of my tests with the KPA100  I am observing a strange
problem.
On 80 and 40m I must not use a Comp setting > 1 (which is off) otherwise
the output jumps to 150W (measured with the LP100 meter)
In CW mode and when I turn Comp off everything is in the normal range.

When I turn the RF power below 10 Watts everything looks fine.
Today I visited my friend OE9FSI and we found out, that he has exactly the
same problem but he never noticed it because he rarely works on SSB and
always had Comp off.

We both have made the SSB modifications to increase mic gain and comp
as described here.
http://www.qrpproject.de/Media/pdf/ZusammenfassungMods.pdf

I have read on the list a note from Don Wilhelm about a problem that seems
related to me which has to do with a  R98 value not being adequate for my
K2, but I am not sure if this is the right trace to solve the problem.

Your help would be very appreciated.

73! de Werner OE9FWV



 
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[Don Wilhelm-4]

Werner,

Part of those modifications is the KI6WX KSB2 Increased RF Gain Mod.  
That mod worked fine with the QRP K2, but after the KPA100 was out for a
while, some folks noticed that they had the same problem that you
describe when the mod was installed.

The problem is that the ALC circuits on the KSB2 board are being
overdriven.  Add the following changes:
On the KSB2 board, 1) change R9 to 1.5k; 2) break the path from KSB2
board P1 pin 6 to the base of Q1 and insert a 1k resistor from P1-6 to
the Q1 base.

Those additions should calm the behavior down to normal.

73,
Don W3FPR

Dr. Werner Furlan wrote:

> hello to the group,
>
> since the beginning of my tests with the KPA100  I am observing a strange
> problem.
> On 80 and 40m I must not use a Comp setting > 1 (which is off) otherwise
> the output jumps to 150W (measured with the LP100 meter)
> In CW mode and when I turn Comp off everything is in the normal range.
>
> When I turn the RF power below 10 Watts everything looks fine.
> Today I visited my friend OE9FSI and we found out, that he has exactly the
> same problem but he never noticed it because he rarely works on SSB and
> always had Comp off.
>
> We both have made the SSB modifications to increase mic gain and comp
> as described here.
> http://www.qrpproject.de/Media/pdf/ZusammenfassungMods.pdf
>
> I have read on the list a note from Don Wilhelm about a problem that seems
> related to me which has to do with a  R98 value not being adequate for my
> K2, but I am not sure if this is the right trace to solve the problem.
>
> Your help would be very appreciated.
>
> 73! de Werner OE9FWV
>
>
>  
>  

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[oe9fwv]

dear Don,

thank you very much for the clear and quick response!
This is really not hard to do and I will report if it helps. (up to now all your
hints were vy helpful ;-))

will this have a negative influence on the Mic gain in QRP mode?


73! de Werner OE9FWV


Don Wilhelm schrieb am 17 Feb 2008 um 14:47:

>
> Part of those modifications is the KI6WX KSB2 Increased RF Gain Mod.  That
> mod worked fine with the QRP K2, but after the KPA100 was out for a while,
> some folks noticed that they had the same problem that you describe when
> the mod was installed.
>
> The problem is that the ALC circuits on the KSB2 board are being
> overdriven.  Add the following changes:
> On the KSB2 board, 1) change R9 to 1.5k; 2) break the path from KSB2
> board P1 pin 6 to the base of Q1 and insert a 1k resistor from P1-6 to the
> Q1 base.
>
> Those additions should calm the behavior down to normal.

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[Don Wilhelm-4]

Werner,

No influence on the mic gain at all.

73,
Don W3FPR

Dr. Werner Furlan wrote:

> dear Don,
>
> thank you very much for the clear and quick response!
> This is really not hard to do and I will report if it helps. (up to now all your
> hints were vy helpful ;-))
>
> will this have a negative influence on the Mic gain in QRP mode?
>
>
> 73! de Werner OE9FWV
>
>
> Don Wilhelm schrieb am 17 Feb 2008 um 14:47:
>
>  
>> Part of those modifications is the KI6WX KSB2 Increased RF Gain Mod.  That
>> mod worked fine with the QRP K2, but after the KPA100 was out for a while,
>> some folks noticed that they had the same problem that you describe when
>> the mod was installed.
>>
>> The problem is that the ALC circuits on the KSB2 board are being
>> overdriven.  Add the following changes:
>> On the KSB2 board, 1) change R9 to 1.5k; 2) break the path from KSB2
>> board P1 pin 6 to the base of Q1 and insert a 1k resistor from P1-6 to the
>> Q1 base.
>>
>> Those additions should calm the behavior down to normal.
>>    
>
>
>  

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[oe9fwv]

hi Don,

Don Wilhelm schrieb am 17 Feb 2008 um 14:47:
 
> The problem is that the ALC circuits on the KSB2 board are being
> overdriven.  Add the following changes:
> On the KSB2 board, 1) change R9 to 1.5k; 2) break the path from KSB2
> board P1 pin 6 to the base of Q1 and insert a 1k resistor from P1-6 to the
> Q1 base.
>
> Those additions should calm the behavior down to normal.

the 1k from P1-6 to base of Q1 was already in place from my earlier mod,
but the change of R9 really cured the problem. All ok now, with Comp up to
4!

thank you very much, that was really easy to do. (if you know where)


73! de Werner OE9FWV

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