K3, KPA500 - PIN Diode Failure in KPA When K3 Subrx Turned on During Xmit?

[John K3TN]

Here's the set up: K3 to KPA500 to KAT500, all Aux bus connections. Began to have high attenuation on receive when the KPA500 was turned from STBY to OPER. Determined by Elecraft to be a blown PIN diode, which makes sense. But why did the PIN diode blow?

Could be that it just failed, could be I mistakenly QSYed and transmitted with KPA at high power before KAT was tuned for new band. But I also remember this scenario happening a few times before I noticed the RX attentuation:

Running N1MM software in a CW contest. I was transmitting some N1MM message and while transmitting went to hit the ESC key to do something and instead hit the ` key, which in N1MM turns on the sub-RX in the K3.  In the heat of a contest exchange, hard to remember exactly what happened but I think that did cause a hard fault with the KPA. Not long after that the PIN diode was blown.

Craig, the guy who repaired my KPA, said he didn't see how an inbound SUBRX ON command to the K3 while transmitting cause lead to a condition where the K3 is transmitting into the KPA while the KPA is in RX mode, but I'd figured I'd cast a wider net to see if it triggers any possible thoughts. I'm also cross-posting to the N1MM reflector.

John K3TN

[ke9uw]

I had a blown pin diode in the PA after about two months of getting the KPA. I didn't do any thing notable to cause it...just happened.

Chuck, KE9UW
AARL, CCA
Lionel Trains TCA, LCCA, LRRC
aka Jack, BMW Motorcycles BMWRA, BMWMOA #224
________________________________________
From: [hidden email] [[hidden email]] on behalf of John K3TN [[hidden email]]
Sent: Friday, February 22, 2013 7:44 AM
To: [hidden email]
Subject: [Elecraft] K3, KPA500 - PIN Diode Failure in KPA When K3 Subrx Turned on During Xmit?

Here's the set up: K3 to KPA500 to KAT500, all Aux bus connections. Began to
have high attenuation on receive when the KPA500 was turned from STBY to
OPER. Determined by Elecraft to be a blown PIN diode, which makes sense. But
why did the PIN diode blow?

Could be that it just failed, could be I mistakenly QSYed and transmitted
with KPA at high power before KAT was tuned for new band. But I also
remember this scenario happening a few times before I noticed the RX
attentuation:

Running N1MM software in a CW contest. I was transmitting some N1MM message
and while transmitting went to hit the ESC key to do something and instead
hit the ` key, which in N1MM turns on the sub-RX in the K3.  In the heat of
a contest exchange, hard to remember exactly what happened but I think that
did cause a hard fault with the KPA. Not long after that the PIN diode was
blown.

Craig, the guy who repaired my KPA, said he didn't see how an inbound SUBRX
ON command to the K3 while transmitting cause lead to a condition where the
K3 is transmitting into the KPA while the KPA is in RX mode, but I'd figured
I'd cast a wider net to see if it triggers any possible thoughts. I'm also
cross-posting to the N1MM reflector.

John K3TN



--
View this message in context: http://elecraft.365791.n2.nabble.com/K3-KPA500-PIN-Diode-Failure-in-KPA-When-K3-Subrx-Turned-on-During-Xmit-tp7570227.html
Sent from the Elecraft mailing list archive at Nabble.com.
______________________________________________________________
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
______________________________________________________________
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

[ke9uw]

My antennas are always dc grounded and i lost a pin diode.


Sent from my iPad
Chuck, KE9UW
(Jack for BMW motorcycles)

On Feb 22, 2013, at 12:12 PM, "Ron D'Eau Claire" <[hidden email]> wrote:

> Are you keeping your antennas grounded when they are not in use? It does not
> take low humidity or wind or rain or snow to put an electric charge on your
> antenna if it's well insulated. The action of the earth's atmosphere
> maintains a huge charge between the ionosphere and the ground - almost
> 400,000 volts - in spite of a constant leakage current through the
> atmosphere from the ionosphere to ground of over 1,500 amperes. Near the
> ground the voltage gradient is close to 100 volts per yard of altitude.
> Given some time, depending upon the number of free ions in the air, an
> insulated antenna will lose electrons until is develops the voltage
> associated with its height above ground. And then, "pow" when you connect
> the antenna to a piece of equipment and electrons from the earth rush in.
> The amount of current is proportional to the mass of the insulated antenna.
>
> Nowadays any metal high above the ground in buildings is connected to an
> earth ground, but in the past that was not always so, and workers were
> occasionally shocked when they touched metal even on a dead calm day.
>
> At least one Ham, troubled by almost constant high-level popping QRN,
> finally traced the source to a large copper cupola roof on his home that was
> not grounded. At night, he could see occasional flashes of sparks from the
> roof to nearby grounded metal even though the air was still. Bonding them
> together fixed it.
>
> Usually these currents are so small that you are not aware of them, but the
> voltages can be enough to puncture sensitive semiconductor gates and
> junctions. The most sensitive areas in most rigs are in the diodes used in
> the SWR bridge at the antenna jack or in diodes used in T/R switches. Other
> semiconductors in a typical rig may be more sensitive to damage, but they
> are well protected by the intervening circuits between them and the antenna
> connector that provide a d-c path to ground.  
>
> If an antenna has been left floating, connect it to an earth ground for a
> moment before you connect it to the rig.
>
> Good quality antenna switches provide a d-c path to bleed off the charge as
> it accumulates. The KAT500, for example, provides such a d-c ground path
> whenever it is turned off and for any antennas connected that are not in
> use.
>
> 73, Ron AC7AC
>
>
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of John K3TN
> Sent: Friday, February 22, 2013 5:45 AM
> To: [hidden email]
> Subject: [Elecraft] K3, KPA500 - PIN Diode Failure in KPA When K3 Subrx
> Turned on During Xmit?
>
> Here's the set up: K3 to KPA500 to KAT500, all Aux bus connections. Began to
> have high attenuation on receive when the KPA500 was turned from STBY to
> OPER. Determined by Elecraft to be a blown PIN diode, which makes sense. But
> why did the PIN diode blow?
>
> Could be that it just failed, could be I mistakenly QSYed and transmitted
> with KPA at high power before KAT was tuned for new band. But I also
> remember this scenario happening a few times before I noticed the RX
> attentuation:
>
> Running N1MM software in a CW contest. I was transmitting some N1MM message
> and while transmitting went to hit the ESC key to do something and instead
> hit the ` key, which in N1MM turns on the sub-RX in the K3.  In the heat of
> a contest exchange, hard to remember exactly what happened but I think that
> did cause a hard fault with the KPA. Not long after that the PIN diode was
> blown.
>
> Craig, the guy who repaired my KPA, said he didn't see how an inbound SUBRX
> ON command to the K3 while transmitting cause lead to a condition where the
> K3 is transmitting into the KPA while the KPA is in RX mode, but I'd figured
> I'd cast a wider net to see if it triggers any possible thoughts. I'm also
> cross-posting to the N1MM reflector.
>
> John K3TN
>
>
>
> ______________________________________________________________
> 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

______________________________________________________________
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

[K9IR]

My experience is very similar to Chuck's KE9UW. My less than 2 month old KPA500 was living life merrily and then, for no reason I can determine, caused my RX signals to drop an S unit or more in Oper mode--most noticeably on 80M.

The amp now is at the doctor (aka Elecraft support) awaiting final diagnosis, but the preliminary analysis is that the pin diodes went poof. I hate to go Gus Grissom on this but they "just blew." I had none of the dramatics of hitting the wrong button in N1MM or having the coax drop off just before TX into infinite VSWR--none of that excitement. I wish I had, so I'd know what not to do next time ;-).

73 Paula K9IR

[ke9uw]

Sure. Should have said that. Just more FYI.

Sent from my iPad
Chuck, KE9UW
(Jack for BMW motorcycles)

On Feb 22, 2013, at 1:15 PM, "Ron D'Eau Claire" <[hidden email]> wrote:

> I certainly did not mean to imply that parts never fail without any apparent
> reason.
>
> My point was that there are circumstances that can make failures much more
> likely.
>
> 73, Ron AC7AC
>
> -----Original Message-----
> From: hawley, charles j jr [mailto:[hidden email]]
> Sent: Friday, February 22, 2013 10:34 AM
> To: Ron D'Eau Claire
> Cc: John K3TN; [hidden email]
> Subject: Re: [Elecraft] K3, KPA500 - PIN Diode Failure in KPA When K3 Subrx
> Turned on During Xmit?
>
> My antennas are always dc grounded and i lost a pin diode.
>
>
> Sent from my iPad
> Chuck, KE9UW
> (Jack for BMW motorcycles)
>
> ______________________________________________________________
> 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

______________________________________________________________
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