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My K2/100 keeps resetting at high power

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Hisashi T Fujinaka

My K2/100 keeps resetting at high power

OK, it's S/N 4355 with all the latest mods and it used to just reset
when I got on 15M phone. Now it's resetting on 30M CW while I'm trying
to work DX so it's bugging me. :)

Besides the standard checking for 10-year-old cold solder joints, is
there anything else to check right away?

--
Hisashi T Fujinaka - [hidden email]
BSEE(6/86) + BSChem(3/95) + BAEnglish(8/95) + MSCS(8/03) + $2.50 = latte
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Eric Swartz - WA6HHQ

Re: My K2/100 keeps resetting at high power

Administrator

Hi Hisashi,

Could it be your power supply? It could either be hitting a max current limit, or getting RF back into the supply. The latter is common with some supplies.

One other area to look at is the 12V power cord and fuse holders. If the cord is too small, or the fuse holders are not making good contact, there could be an excessive voltage drop under load.

You can check for this by watching the K2's voltage display as you increase power. Some drop is normal, but an excessive multi-volt drop indicates a problem with the supply or cables.

73,
Eric

www.elecraft.com
_..._

On Apr 2, 2012, at 8:37 AM, Hisashi T Fujinaka <[hidden email]> wrote:

> OK, it's S/N 4355 with all the latest mods and it used to just reset
> when I got on 15M phone. Now it's resetting on 30M CW while I'm trying
> to work DX so it's bugging me. :)
>
> Besides the standard checking for 10-year-old cold solder joints, is
> there anything else to check right away?
>
>
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Don Wilhelm-4

Re: My K2/100 keeps resetting at high power

In reply to this post by Hisashi T Fujinaka

Hisashi,

If by "reset" you mean the power turns off, you are most likely seeing
the internal resettable fuse trip.
Normally you would see a HiCur message too.
Usual causes for that behavior are either that the KPA100 wattmeter
diodes have been damaged or you have a damaged PA transistor in the base K2.

Check the actual output power --
Connect an external wattmeter between the KPA100 and a dummy load then
set the K2 power knob to about 30 watts. set to CW and hold the key
down long enough to read the external wattmeter. If it shows full power
output (greater than 100 watts), you have a problem with the wattmeter
in the KPA100 - most likely bad diodes at D16 and D17.

73,
Don W3FPR

On 4/2/2012 11:37 AM, Hisashi T Fujinaka wrote:
> OK, it's S/N 4355 with all the latest mods and it used to just reset
> when I got on 15M phone. Now it's resetting on 30M CW while I'm trying
> to work DX so it's bugging me. :)
>
> Besides the standard checking for 10-year-old cold solder joints, is
> there anything else to check right away?
>
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Hisashi T Fujinaka

Re: My K2/100 keeps resetting at high power

I think I see HiRefl even though at lower power I saw lower than 2:1
SWR. I do have an SWR meter external to the K2. I'll look to see what it
tells me.

Thanks!

On Mon, 2 Apr 2012, Don Wilhelm wrote:

> Hisashi,
>
> If by "reset" you mean the power turns off, you are most likely seeing the
> internal resettable fuse trip.
> Normally you would see a HiCur message too.
> Usual causes for that behavior are either that the KPA100 wattmeter diodes
> have been damaged or you have a damaged PA transistor in the base K2.
>
> Check the actual output power --
> Connect an external wattmeter between the KPA100 and a dummy load then set
> the K2 power knob to about 30 watts. set to CW and hold the key down long
> enough to read the external wattmeter. If it shows full power output
> (greater than 100 watts), you have a problem with the wattmeter in the KPA100
> - most likely bad diodes at D16 and D17.
>
> 73,
> Don W3FPR
>
>
> On 4/2/2012 11:37 AM, Hisashi T Fujinaka wrote:
>> OK, it's S/N 4355 with all the latest mods and it used to just reset
>> when I got on 15M phone. Now it's resetting on 30M CW while I'm trying
>> to work DX so it's bugging me. :)
>>
>> Besides the standard checking for 10-year-old cold solder joints, is
>> there anything else to check right away?
>>
>

--
Hisashi T Fujinaka - [hidden email]
BSEE(6/86) + BSChem(3/95) + BAEnglish(8/95) + MSCS(8/03) + $2.50 = latte
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Hisashi T Fujinaka

Re: My K2/100 keeps resetting at high power

In reply to this post by Don Wilhelm-4

After getting the suggestions from Eric and you, I looked at the
metering I have already.

I don't think it's the SWR bridge because the power reading matches the
wattmeter on my MFJ-1788. It steadily increases and looks about the same
as what the K2 shows.

However, the voltage/current meter I get to from the DISPLAY button is
odd. As I turn up the power before the KPA100 kicks in, I get an
increasing current up to 2.5. Then the current reading drops to 1.5 and
stays there. The metering of my power supply shows increasing current
and everything resets itself when it gets ~15-20A.

Time to look for the schematics, but any suggestions would be
appreciated.

On Mon, 2 Apr 2012, Don Wilhelm wrote:

Don Wilhelm-4

Re: My K2/100 keeps resetting at high power

Hisashi,

OK, so that sounds like the KPA100 may be oscillating. First things to
check are the diodes in the T/R switch, the high voltage bias supply
(check during transmit too) and the operation of Q6 and Q7.

Is this the newer KPA100 design with blue toroid cores at L16 and RFC1?
If not, you will want to install KPA100UPKT, it was designed to combat
an oscillation tendency.

73,
Don W3FPR

On 4/2/2012 8:19 PM, Hisashi T Fujinaka wrote:

> After getting the suggestions from Eric and you, I looked at the
> metering I have already.
>
> I don't think it's the SWR bridge because the power reading matches the
> wattmeter on my MFJ-1788. It steadily increases and looks about the same
> as what the K2 shows.
>
> However, the voltage/current meter I get to from the DISPLAY button is
> odd. As I turn up the power before the KPA100 kicks in, I get an
> increasing current up to 2.5. Then the current reading drops to 1.5 and
> stays there. The metering of my power supply shows increasing current
> and everything resets itself when it gets ~15-20A.
>
> Time to look for the schematics, but any suggestions would be
> appreciated.
>
> On Mon, 2 Apr 2012, Don Wilhelm wrote:
>
>> Hisashi,
>>
>> If by "reset" you mean the power turns off, you are most likely seeing the
>> internal resettable fuse trip.
>> Normally you would see a HiCur message too.
>> Usual causes for that behavior are either that the KPA100 wattmeter diodes
>> have been damaged or you have a damaged PA transistor in the base K2.
>>
>> Check the actual output power --
>> Connect an external wattmeter between the KPA100 and a dummy load then set
>> the K2 power knob to about 30 watts. set to CW and hold the key down long
>> enough to read the external wattmeter. If it shows full power output
>> (greater than 100 watts), you have a problem with the wattmeter in the KPA100
>> - most likely bad diodes at D16 and D17.
>>
>> 73,
>> Don W3FPR
>>
>>
>> On 4/2/2012 11:37 AM, Hisashi T Fujinaka wrote:
>>> OK, it's S/N 4355 with all the latest mods and it used to just reset
>>> when I got on 15M phone. Now it's resetting on 30M CW while I'm trying
>>> to work DX so it's bugging me. :)
>>>
>>> Besides the standard checking for 10-year-old cold solder joints, is
>>> there anything else to check right away?
>>>

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Hisashi T Fujinaka

Re: My K2/100 keeps resetting at high power

I just installed the KPA100UPKT about a month ago.

Just to be clear, as I turn up the power, the internal metering shows
1.5A while the external metering shows the current increasing as the
power increases.

I'll check the voltages around the diodes and the HV bias supply to
begin with. Thanks for the pointers.

On Mon, 2 Apr 2012, Don Wilhelm wrote:

> Hisashi,
>
> OK, so that sounds like the KPA100 may be oscillating. First things to check
> are the diodes in the T/R switch, the high voltage bias supply (check during
> transmit too) and the operation of Q6 and Q7.
>
> Is this the newer KPA100 design with blue toroid cores at L16 and RFC1? If
> not, you will want to install KPA100UPKT, it was designed to combat an
> oscillation tendency.
>
> 73,
> Don W3FPR
>
> On 4/2/2012 8:19 PM, Hisashi T Fujinaka wrote:
>> After getting the suggestions from Eric and you, I looked at the
>> metering I have already.
>>
>> I don't think it's the SWR bridge because the power reading matches the
>> wattmeter on my MFJ-1788. It steadily increases and looks about the same
>> as what the K2 shows.
>>
>> However, the voltage/current meter I get to from the DISPLAY button is
>> odd. As I turn up the power before the KPA100 kicks in, I get an
>> increasing current up to 2.5. Then the current reading drops to 1.5 and
>> stays there. The metering of my power supply shows increasing current
>> and everything resets itself when it gets ~15-20A.
>>
>> Time to look for the schematics, but any suggestions would be
>> appreciated.
>>
>> On Mon, 2 Apr 2012, Don Wilhelm wrote:
>>
>>> Hisashi,
>>>
>>> If by "reset" you mean the power turns off, you are most likely seeing the
>>> internal resettable fuse trip.
>>> Normally you would see a HiCur message too.
>>> Usual causes for that behavior are either that the KPA100 wattmeter diodes
>>> have been damaged or you have a damaged PA transistor in the base K2.
>>>
>>> Check the actual output power --
>>> Connect an external wattmeter between the KPA100 and a dummy load then set
>>> the K2 power knob to about 30 watts. set to CW and hold the key down long
>>> enough to read the external wattmeter. If it shows full power output
>>> (greater than 100 watts), you have a problem with the wattmeter in the
>>> KPA100
>>> - most likely bad diodes at D16 and D17.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>>
>>> On 4/2/2012 11:37 AM, Hisashi T Fujinaka wrote:
>>>> OK, it's S/N 4355 with all the latest mods and it used to just reset
>>>> when I got on 15M phone. Now it's resetting on 30M CW while I'm trying
>>>> to work DX so it's bugging me. :)
>>>>
>>>> Besides the standard checking for 10-year-old cold solder joints, is
>>>> there anything else to check right away?
>>>>
>

Don Wilhelm-4

Re: My K2/100 keeps resetting at high power

Hisashi,

The current indicated by tapping the DISPLAY button is the current drawn
by the base K2, and not the current into the KPA100. Your 2.5 amp
current at 10 watts is normal, as is the drop in current as you go into
the KPA100 "is on" stage because at low KPA100 power levels, the base K2
does not have to drive the KPA100 very hard.

I would suggest starting with the DC Diode voltage measurements - use
the values in the new KPA100 manual rather than your printed one - the
chart in your old manual is no longer good.

Make certain the HV bias supply voltage stays "up to par" during transmit.

If you have a 'scope, observe the RF output carefully with an eye on the
time-base of the 'scope so you can try to determine the frequency (even
if relevant) of good transmission vs. the frequency when it begins to
draw more current. If it is oscillating, determining the approximate
frequency of oscillation can be helpful.

This is not an easy thing to troubleshoot, I wish you luck.

73,
Don W3FPR

On 4/2/2012 9:39 PM, Hisashi T Fujinaka wrote:

> I just installed the KPA100UPKT about a month ago.
>
> Just to be clear, as I turn up the power, the internal metering shows
> 1.5A while the external metering shows the current increasing as the
> power increases.
>
> I'll check the voltages around the diodes and the HV bias supply to
> begin with. Thanks for the pointers.
>
> On Mon, 2 Apr 2012, Don Wilhelm wrote:
>
>> Hisashi,
>>
>> OK, so that sounds like the KPA100 may be oscillating. First things to check
>> are the diodes in the T/R switch, the high voltage bias supply (check during
>> transmit too) and the operation of Q6 and Q7.
>>
>> Is this the newer KPA100 design with blue toroid cores at L16 and RFC1? If
>> not, you will want to install KPA100UPKT, it was designed to combat an
>> oscillation tendency.
>>
>> 73,
>> Don W3FPR
>>
>> On 4/2/2012 8:19 PM, Hisashi T Fujinaka wrote:
>>> After getting the suggestions from Eric and you, I looked at the
>>> metering I have already.
>>>
>>> I don't think it's the SWR bridge because the power reading matches the
>>> wattmeter on my MFJ-1788. It steadily increases and looks about the same
>>> as what the K2 shows.
>>>
>>> However, the voltage/current meter I get to from the DISPLAY button is
>>> odd. As I turn up the power before the KPA100 kicks in, I get an
>>> increasing current up to 2.5. Then the current reading drops to 1.5 and
>>> stays there. The metering of my power supply shows increasing current
>>> and everything resets itself when it gets ~15-20A.
>>>
>>> Time to look for the schematics, but any suggestions would be
>>> appreciated.
>>>
>>> On Mon, 2 Apr 2012, Don Wilhelm wrote:
>>>
>>>> Hisashi,
>>>>
>>>> If by "reset" you mean the power turns off, you are most likely seeing the
>>>> internal resettable fuse trip.
>>>> Normally you would see a HiCur message too.
>>>> Usual causes for that behavior are either that the KPA100 wattmeter diodes
>>>> have been damaged or you have a damaged PA transistor in the base K2.
>>>>
>>>> Check the actual output power --
>>>> Connect an external wattmeter between the KPA100 and a dummy load then set
>>>> the K2 power knob to about 30 watts. set to CW and hold the key down long
>>>> enough to read the external wattmeter. If it shows full power output
>>>> (greater than 100 watts), you have a problem with the wattmeter in the
>>>> KPA100
>>>> - most likely bad diodes at D16 and D17.
>>>>
>>>> 73,
>>>> Don W3FPR
>>>>
>>>>
>>>> On 4/2/2012 11:37 AM, Hisashi T Fujinaka wrote:
>>>>> OK, it's S/N 4355 with all the latest mods and it used to just reset
>>>>> when I got on 15M phone. Now it's resetting on 30M CW while I'm trying
>>>>> to work DX so it's bugging me. :)
>>>>>
>>>>> Besides the standard checking for 10-year-old cold solder joints, is
>>>>> there anything else to check right away?
>>>>>

Hisashi T Fujinaka

Re: My K2/100 keeps resetting at high power

Just to follow up on this for anyone who might be searching the
archives, the problem was traced to the power supply. It was undersized
and wasn't what everyone remembered it as being, and after being pulled
out from under the desk it turned out to be an Astron 20, rather than an
Astron 35.

On Mon, 2 Apr 2012, Don Wilhelm wrote:

> Hisashi,
>
> The current indicated by tapping the DISPLAY button is the current drawn by
> the base K2, and not the current into the KPA100. Your 2.5 amp current at 10
> watts is normal, as is the drop in current as you go into the KPA100 "is on"
> stage because at low KPA100 power levels, the base K2 does not have to drive
> the KPA100 very hard.
>
> I would suggest starting with the DC Diode voltage measurements - use the
> values in the new KPA100 manual rather than your printed one - the chart in
> your old manual is no longer good.
>
> Make certain the HV bias supply voltage stays "up to par" during transmit.
>
> If you have a 'scope, observe the RF output carefully with an eye on the
> time-base of the 'scope so you can try to determine the frequency (even if
> relevant) of good transmission vs. the frequency when it begins to draw more
> current. If it is oscillating, determining the approximate frequency of
> oscillation can be helpful.
>
> This is not an easy thing to troubleshoot, I wish you luck.
>
> 73,
> Don W3FPR
>
>
> On 4/2/2012 9:39 PM, Hisashi T Fujinaka wrote:
>> I just installed the KPA100UPKT about a month ago.
>>
>> Just to be clear, as I turn up the power, the internal metering shows
>> 1.5A while the external metering shows the current increasing as the
>> power increases.
>>
>> I'll check the voltages around the diodes and the HV bias supply to
>> begin with. Thanks for the pointers.
>>
>> On Mon, 2 Apr 2012, Don Wilhelm wrote:
>>
>>> Hisashi,
>>>
>>> OK, so that sounds like the KPA100 may be oscillating. First things to
>>> check
>>> are the diodes in the T/R switch, the high voltage bias supply (check
>>> during
>>> transmit too) and the operation of Q6 and Q7.
>>>
>>> Is this the newer KPA100 design with blue toroid cores at L16 and RFC1?
>>> If
>>> not, you will want to install KPA100UPKT, it was designed to combat an
>>> oscillation tendency.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>> On 4/2/2012 8:19 PM, Hisashi T Fujinaka wrote:
>>>> After getting the suggestions from Eric and you, I looked at the
>>>> metering I have already.
>>>>
>>>> I don't think it's the SWR bridge because the power reading matches the
>>>> wattmeter on my MFJ-1788. It steadily increases and looks about the same
>>>> as what the K2 shows.
>>>>
>>>> However, the voltage/current meter I get to from the DISPLAY button is
>>>> odd. As I turn up the power before the KPA100 kicks in, I get an
>>>> increasing current up to 2.5. Then the current reading drops to 1.5 and
>>>> stays there. The metering of my power supply shows increasing current
>>>> and everything resets itself when it gets ~15-20A.
>>>>
>>>> Time to look for the schematics, but any suggestions would be
>>>> appreciated.
>>>>
>>>> On Mon, 2 Apr 2012, Don Wilhelm wrote:
>>>>
>>>>> Hisashi,
>>>>>
>>>>> If by "reset" you mean the power turns off, you are most likely seeing
>>>>> the
>>>>> internal resettable fuse trip.
>>>>> Normally you would see a HiCur message too.
>>>>> Usual causes for that behavior are either that the KPA100 wattmeter
>>>>> diodes
>>>>> have been damaged or you have a damaged PA transistor in the base K2.
>>>>>
>>>>> Check the actual output power --
>>>>> Connect an external wattmeter between the KPA100 and a dummy load then
>>>>> set
>>>>> the K2 power knob to about 30 watts. set to CW and hold the key down
>>>>> long
>>>>> enough to read the external wattmeter. If it shows full power output
>>>>> (greater than 100 watts), you have a problem with the wattmeter in the
>>>>> KPA100
>>>>> - most likely bad diodes at D16 and D17.
>>>>>
>>>>> 73,
>>>>> Don W3FPR
>>>>>
>>>>>
>>>>> On 4/2/2012 11:37 AM, Hisashi T Fujinaka wrote:
>>>>>> OK, it's S/N 4355 with all the latest mods and it used to just reset
>>>>>> when I got on 15M phone. Now it's resetting on 30M CW while I'm trying
>>>>>> to work DX so it's bugging me. :)
>>>>>>
>>>>>> Besides the standard checking for 10-year-old cold solder joints, is
>>>>>> there anything else to check right away?
>>>>>>
>

K1FFX

Re: My K2/100 keeps resetting at high power

I'm glad that switching to a bigger Astron supply solved your problem. I would
note, however, that I've been running my KPA100 with an Astron 20 at the 100
watt level for the past year with no problems.

Best regards -

Bruce K1FFX

Bruce Rosen
K1FFX
K2/100 6982 KSB2 KAT100-1 KAF2 KIO2

Rick WA6NHC

Re: My K2/100 keeps resetting at high power

Ditto here with my K3/100, except that the Astron 20 recently developed a
bad habit of crowbar'ing when I get on 20 meters with the KPA500. Slams off
IMMEDIATELY on transmit with the amp. I guess it doesn't like 500+ watts @
20' (my vertical). Waiting for the KAT500, which will resolve that issue
(the wire antenna is 60' away but requires a tuner). :-\

73,
Rick wa6nhc

-----Original Message-----
From: K1FFX

I'm glad that switching to a bigger Astron supply solved your problem. I
would note, however, that I've been running my KPA100 with an Astron 20 at
the 100 watt level for the past year with no problems.

Best regards -

Bruce K1FFX

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