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KPA/100 displays wrong PS current (much lower)

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Ioannis Kassotakis

KPA/100 displays wrong PS current (much lower)

Just finished building the KPA-100 for my S/N 2102 K2 (MCU v. 2.03D, KPA
1.06)
The K2/100 does not display the correct 13.8 V power supply current (by
taping Display) when it switches to HI POWER (>10 Watts).
I used a DMM in series to accurately measure the PS supplied current while
checking the K2 display at several power settings . Later, I also measured
the KPA TP1 voltage which is the I sense input to the KPA-100 processor.
For several power settings I got:
PWR (Watts) - PS Current (DMM) Amps - K2 Current Display Amps - KPA/100 TP1
(mV)
RX-0.4 - 0.44 - 0 <x-apple-data-detectors://0>
1.0- 1.72- 1.76 -0
5.0 - 3.3-3.3 - 0
10- 3.8 - 3.8 - 0
15- 4.5 - 1.01 - Not measured
20- 5.4 - 1.02 - 100
40 - 7.0 - 1.20 - 250
60 - 8.5 - 1.28 -380
80 - 9.5 - 1.41 - 500
100 - 10.3 - 1.48 - 580
111 - 10.8 - 1.54 - N/A
The measurements were done at 40 m (7.100) at CW to a dummy load through
KAT-100.

It seems to work fine a LO PWR (<11 Watts) but appears to have a scaling
issue, when the PA switches On to HI PWR mode.
According to the schem (p.61) I Sense is supposed to vary 0-5 V for 0-32 A,
so the TP1 figures seem to be rather low.
Is this a known issue? Is it possible that I have a failed U7 or Q5 ?

Thanks!

Ioannis

--
Ioannis Kassotakis
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Don Wilhelm

Re: KPA/100 displays wrong PS current (much lower)

Ioannis,

The current display on the K2 indicates only the current for the base
K2, not for the K2 and KPA100 combination.
That is why you set the CAL CUR to 3.50 amps even though the KPA100 will
draw much more current.

Yes, the KPA100 does have a scaling on the amount of RF voltage that is
being detected. That is used for power control and has nothing to do
with the current displayed. The result of that voltage is sent to the
VRFDET signal in the K2 (Voltage of the RF Detected).

73,
Don W3FPR

On 4/24/2016 12:05 PM, Ioannis Kassotakis wrote:

> Just finished building the KPA-100 for my S/N 2102 K2 (MCU v. 2.03D, KPA
> 1.06)
> The K2/100 does not display the correct 13.8 V power supply current (by
> taping Display) when it switches to HI POWER (>10 Watts).
> I used a DMM in series to accurately measure the PS supplied current while
> checking the K2 display at several power settings . Later, I also measured
> the KPA TP1 voltage which is the I sense input to the KPA-100 processor.
> For several power settings I got:
> PWR (Watts) - PS Current (DMM) Amps - K2 Current Display Amps - KPA/100 TP1
> (mV)
> RX-0.4 - 0.44 - 0 <x-apple-data-detectors://0>
> 1.0- 1.72- 1.76 -0
> 5.0 - 3.3-3.3 - 0
> 10- 3.8 - 3.8 - 0
> 15- 4.5 - 1.01 - Not measured
> 20- 5.4 - 1.02 - 100
> 40 - 7.0 - 1.20 - 250
> 60 - 8.5 - 1.28 -380
> 80 - 9.5 - 1.41 - 500
> 100 - 10.3 - 1.48 - 580
> 111 - 10.8 - 1.54 - N/A
> The measurements were done at 40 m (7.100) at CW to a dummy load through
> KAT-100.
>
> It seems to work fine a LO PWR (<11 Watts) but appears to have a scaling
> issue, when the PA switches On to HI PWR mode.
> According to the schem (p.61) I Sense is supposed to vary 0-5 V for 0-32 A,
> so the TP1 figures seem to be rather low.
> Is this a known issue? Is it possible that I have a failed U7 or Q5 ?
>
>

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Ioannis Kassotakis

Re: KPA/100 displays wrong PS current (much lower)

Thanks Don,
That means that at HI PWR (>11 Watts) should disregard the displayed PS
current figures.
I thought that KPA100 processor would communicate the I Sense back to the
MCU and display the correct current figure after rescaling. I understand
that is not the case.

73,

Ioannis PA1EQP

On Sunday, 24 April 2016, Don Wilhelm <[hidden email]> wrote:

> Ioannis,
>
> The current display on the K2 indicates only the current for the base K2,
> not for the K2 and KPA100 combination.
> That is why you set the CAL CUR to 3.50 amps even though the KPA100 will
> draw much more current.
>
> Yes, the KPA100 does have a scaling on the amount of RF voltage that is
> being detected. That is used for power control and has nothing to do with
> the current displayed. The result of that voltage is sent to the VRFDET
> signal in the K2 (Voltage of the RF Detected).
>
> 73,
> Don W3FPR
>
> On 4/24/2016 12:05 PM, Ioannis Kassotakis wrote:
>
>> Just finished building the KPA-100 for my S/N 2102 K2 (MCU v. 2.03D, KPA
>> 1.06)
>> The K2/100 does not display the correct 13.8 V power supply current (by
>> taping Display) when it switches to HI POWER (>10 Watts).
>> I used a DMM in series to accurately measure the PS supplied current while
>> checking the K2 display at several power settings . Later, I also measured
>> the KPA TP1 voltage which is the I sense input to the KPA-100 processor.
>> For several power settings I got:
>> PWR (Watts) - PS Current (DMM) Amps - K2 Current Display Amps - KPA/100
>> TP1
>> (mV)
>> RX-0.4 - 0.44 - 0 <x-apple-data-detectors://0>
>> 1.0- 1.72- 1.76 -0
>> 5.0 - 3.3-3.3 - 0
>> 10- 3.8 - 3.8 - 0
>> 15- 4.5 - 1.01 - Not measured
>> 20- 5.4 - 1.02 - 100
>> 40 - 7.0 - 1.20 - 250
>> 60 - 8.5 - 1.28 -380
>> 80 - 9.5 - 1.41 - 500
>> 100 - 10.3 - 1.48 - 580
>> 111 - 10.8 - 1.54 - N/A
>> The measurements were done at 40 m (7.100) at CW to a dummy load through
>> KAT-100.
>>
>> It seems to work fine a LO PWR (<11 Watts) but appears to have a scaling
>> issue, when the PA switches On to HI PWR mode.
>> According to the schem (p.61) I Sense is supposed to vary 0-5 V for 0-32
>> A,
>> so the TP1 figures seem to be rather low.
>> Is this a known issue? Is it possible that I have a failed U7 or Q5 ?
>>
>>
>>
>

--
Ioannis Kassotakis
______________________________________________________________
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
Message delivered to [hidden email]

Don Wilhelm

Re: KPA/100 displays wrong PS current (much lower)

The current display on the K2 is only for the current used by the base
K2. I use it when testing the K2 for 'good health' and normal RF Gain,
but during operating I see no need to monitor it on a regular basis.
The Base K2 will indicate Hi Cur if the current draw goes above the
value set by the CAL CUR parameter, and will reduce power if that
occurs. Should you continue to get Hi Cur messages, that is an
indication of something that should be investigated.

73,
Don W3FPR

On 4/24/2016 3:14 PM, Ioannis Kassotakis wrote:

> Thanks Don,
> That means that at HI PWR (>11 Watts) should disregard the displayed
> PS current figures.
> I thought that KPA100 processor would communicate the I Sense back to
> the MCU and display the correct current figure after rescaling. I
> understand that is not the case.
>
> 73,
>
> Ioannis PA1EQP
>
> On Sunday, 24 April 2016, Don Wilhelm <[hidden email]
> <mailto:[hidden email]>> wrote:
>
> Ioannis,
>
> The current display on the K2 indicates only the current for the
> base K2, not for the K2 and KPA100 combination.
> That is why you set the CAL CUR to 3.50 amps even though the
> KPA100 will draw much more current.
>
> Yes, the KPA100 does have a scaling on the amount of RF voltage
> that is being detected. That is used for power control and has
> nothing to do with the current displayed. The result of that
> voltage is sent to the VRFDET signal in the K2 (Voltage of the RF
> Detected).
>
> 73,
> Don W3FPR
>

Ioannis Kassotakis

Re: KPA/100 displays wrong PS current (much lower)

Thanks Don,
I understand that the PS current reading is only for the Base K2.
I will rely on the bench PS display to read the 13.8 DC current.
I have already set the CAL CUR to 3.8 Amps so that I do not get HI CUR
alert at 10 Watts.

73,
Ioannis PA1EQP

On Sunday, 24 April 2016, Don Wilhelm <[hidden email]> wrote:

> The current display on the K2 is only for the current used by the base
> K2. I use it when testing the K2 for 'good health' and normal RF Gain, but
> during operating I see no need to monitor it on a regular basis.
> The Base K2 will indicate Hi Cur if the current draw goes above the value
> set by the CAL CUR parameter, and will reduce power if that occurs. Should
> you continue to get Hi Cur messages, that is an indication of something
> that should be investigated.
>
> 73,
> Don W3FPR
>
> On 4/24/2016 3:14 PM, Ioannis Kassotakis wrote:
>
>> Thanks Don,
>> That means that at HI PWR (>11 Watts) should disregard the displayed PS
>> current figures.
>> I thought that KPA100 processor would communicate the I Sense back to the
>> MCU and display the correct current figure after rescaling. I understand
>> that is not the case.
>>
>> 73,
>>
>> Ioannis PA1EQP
>>
>> On Sunday, 24 April 2016, Don Wilhelm <[hidden email] <mailto:
>> [hidden email]>> wrote:
>>
>> Ioannis,
>>
>> The current display on the K2 indicates only the current for the
>> base K2, not for the K2 and KPA100 combination.
>> That is why you set the CAL CUR to 3.50 amps even though the
>> KPA100 will draw much more current.
>>
>> Yes, the KPA100 does have a scaling on the amount of RF voltage
>> that is being detected. That is used for power control and has
>> nothing to do with the current displayed. The result of that
>> voltage is sent to the VRFDET signal in the K2 (Voltage of the RF
>> Detected).
>>
>> 73,
>> Don W3FPR
>>
>>
>

Don Wilhelm

Re: KPA/100 displays wrong PS current (much lower)

Ioannis,

Back the CAL CUR down to 3.50.
It may be that you will have Hi Cur messages if you turn the POWER knob
to full clockwise, but if you set the power control at 100 watts, that
message should not appear.

If it does, check the connections from the power supply to the
K2/KPA100. If the voltage at the K2 (observe with the K2 voltage
display) drops significantly during keydown, that could explain the Hi
Cur warnings. Tighten the power supply terminals and check to be certain
the APP connector is properly assembled with the connector blades fully
inserted. If you look at the end of the APP connector and can see the
spring blades that normally lock the contact blade, the contact blade
has not been fully inserted and will not make full contact (and cause a
significant voltage drop).
If you can increase your power supply voltage to 14.3 volts or above,
you should increase the voltage. The K2 will operate with voltages up
to 15 volts. For linearity and best transmit IMD, the higher the
voltage, the better.

73,
Don W3FPR

On 4/24/2016 4:07 PM, Ioannis Kassotakis wrote:

> Thanks Don,
> I understand that the PS current reading is only for the Base K2.
> I will rely on the bench PS display to read the 13.8 DC current.
> I have already set the CAL CUR to 3.8 Amps so that I do not get HI CUR
> alert at 10 Watts.
>
> 73,
> Ioannis PA1EQP
>
>
> On Sunday, 24 April 2016, Don Wilhelm <[hidden email]
> <mailto:[hidden email]>> wrote:
>
> The current display on the K2 is only for the current used by the
> base K2. I use it when testing the K2 for 'good health' and
> normal RF Gain, but during operating I see no need to monitor it
> on a regular basis.
> The Base K2 will indicate Hi Cur if the current draw goes above
> the value set by the CAL CUR parameter, and will reduce power if
> that occurs. Should you continue to get Hi Cur messages, that is
> an indication of something that should be investigated.
>
> 73,
> Don W3FPR
>
> On 4/24/2016 3:14 PM, Ioannis Kassotakis wrote:
>
> Thanks Don,
> That means that at HI PWR (>11 Watts) should disregard the
> displayed PS current figures.
> I thought that KPA100 processor would communicate the I Sense
> back to the MCU and display the correct current figure after
> rescaling. I understand that is not the case.
>
> 73,
>
> Ioannis PA1EQP
>
> On Sunday, 24 April 2016, Don Wilhelm <[hidden email]
> <mailto:[hidden email]>> wrote:
>
> Ioannis,
>
> The current display on the K2 indicates only the current
> for the
> base K2, not for the K2 and KPA100 combination.
> That is why you set the CAL CUR to 3.50 amps even though the
> KPA100 will draw much more current.
>
> Yes, the KPA100 does have a scaling on the amount of RF
> voltage
> that is being detected. That is used for power control
> and has
> nothing to do with the current displayed. The result of that
> voltage is sent to the VRFDET signal in the K2 (Voltage of
> the RF
> Detected).
>
> 73,
> Don W3FPR
>
>
>
>
> --
> Ioannis Kassotakis

Ioannis Kassotakis

Re: KPA/100 displays wrong PS current (much lower)

Don,
I think that the voltage drops to 13 V or lower at key down.
I will follow your advice.
Thanks again.

73,

Ioannis PA1EQP

On Monday, 25 April 2016, Don Wilhelm <[hidden email]> wrote:

> Ioannis,
>
> Back the CAL CUR down to 3.50.
> It may be that you will have Hi Cur messages if you turn the POWER knob to
> full clockwise, but if you set the power control at 100 watts, that message
> should not appear.
>
> If it does, check the connections from the power supply to the K2/KPA100.
> If the voltage at the K2 (observe with the K2 voltage display) drops
> significantly during keydown, that could explain the Hi Cur warnings.
> Tighten the power supply terminals and check to be certain the APP
> connector is properly assembled with the connector blades fully inserted.
> If you look at the end of the APP connector and can see the spring blades
> that normally lock the contact blade, the contact blade has not been fully
> inserted and will not make full contact (and cause a significant voltage
> drop).
> If you can increase your power supply voltage to 14.3 volts or above, you
> should increase the voltage. The K2 will operate with voltages up to 15
> volts. For linearity and best transmit IMD, the higher the voltage, the
> better.
>
> 73,
> Don W3FPR
>
> On 4/24/2016 4:07 PM, Ioannis Kassotakis wrote:
>
>> Thanks Don,
>> I understand that the PS current reading is only for the Base K2.
>> I will rely on the bench PS display to read the 13.8 DC current.
>> I have already set the CAL CUR to 3.8 Amps so that I do not get HI CUR
>> alert at 10 Watts.
>>
>> 73,
>> Ioannis PA1EQP
>>
>>
>> On Sunday, 24 April 2016, Don Wilhelm <[hidden email] <mailto:
>> [hidden email]>> wrote:
>>
>> The current display on the K2 is only for the current used by the
>> base K2. I use it when testing the K2 for 'good health' and
>> normal RF Gain, but during operating I see no need to monitor it
>> on a regular basis.
>> The Base K2 will indicate Hi Cur if the current draw goes above
>> the value set by the CAL CUR parameter, and will reduce power if
>> that occurs. Should you continue to get Hi Cur messages, that is
>> an indication of something that should be investigated.
>>
>> 73,
>> Don W3FPR
>>
>> On 4/24/2016 3:14 PM, Ioannis Kassotakis wrote:
>>
>> Thanks Don,
>> That means that at HI PWR (>11 Watts) should disregard the
>> displayed PS current figures.
>> I thought that KPA100 processor would communicate the I Sense
>> back to the MCU and display the correct current figure after
>> rescaling. I understand that is not the case.
>>
>> 73,
>>
>> Ioannis PA1EQP
>>
>> On Sunday, 24 April 2016, Don Wilhelm <[hidden email]
>> <mailto:[hidden email]>> wrote:
>>
>> Ioannis,
>>
>> The current display on the K2 indicates only the current
>> for the
>> base K2, not for the K2 and KPA100 combination.
>> That is why you set the CAL CUR to 3.50 amps even though the
>> KPA100 will draw much more current.
>>
>> Yes, the KPA100 does have a scaling on the amount of RF
>> voltage
>> that is being detected. That is used for power control
>> and has
>> nothing to do with the current displayed. The result of that
>> voltage is sent to the VRFDET signal in the K2 (Voltage of
>> the RF
>> Detected).
>>
>> 73,
>> Don W3FPR
>>
>>
>>
>>
>> --
>> Ioannis Kassotakis
>>
>
>