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Sudden KpA1500 power reduction

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Dana Roode

Sudden KpA1500 power reduction

I'm in the ARRL CW contest this weekend and the KPA1500 has been working
fine. However, a few minutes ago I noticed I was getting about half the
output power on 20 meters that I typically get with around 30 watts drive
(about 600w vs 1200w). PA current is less than normal, around 30a.
Similar problem on the higher bands, I can no longer get 1000w. On 40m I
can, but it requires more drive.

Seems like something died in the amp; I'm not familiar with the design, but
perhaps an output module. No errors or ill behavior from the amp other
than the loss of power.

I will contact Elecraft support unless there is something I'm missing
here. I just looked in the archive and see that this has happened to
others.... I use the amp remotely so I guess I'll have to take it home
with me.

Dana
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Dave wo2x

Re: Sudden KpA1500 power reduction

Just my guess is one of the LDMOS devices let out the magic smoke?
Just a thought...

Dave wo2x

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Dana Roode K6NR
Sent: Saturday, February 20, 2021 9:16 PM
To: Elecraft Reflector <[hidden email]>
Subject: [Elecraft] Sudden KpA1500 power reduction

I'm in the ARRL CW contest this weekend and the KPA1500 has been working
fine. However, a few minutes ago I noticed I was getting about half the
output power on 20 meters that I typically get with around 30 watts drive
(about 600w vs 1200w). PA current is less than normal, around 30a.
Similar problem on the higher bands, I can no longer get 1000w. On 40m I
can, but it requires more drive.

Seems like something died in the amp; I'm not familiar with the design, but
perhaps an output module. No errors or ill behavior from the amp other than
the loss of power.

I will contact Elecraft support unless there is something I'm missing here.
I just looked in the archive and see that this has happened to others.... I
use the amp remotely so I guess I'll have to take it home with me.

Dana
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Frank Scolaro

Re: Sudden KpA1500 power reduction

In reply to this post by Dana Roode

Happened to me several months ago... one LDMOS out! same symptoms. You need the power with such great band conditions...

GL
Frank, W2YK

-----Original Message-----

>From: [hidden email]
>Sent: Feb 21, 2021 12:23 PM
>To: 'Dana Roode K6NR' <[hidden email]>, 'Elecraft Reflector' <[hidden email]>
>Subject: Re: [Elecraft] Sudden KpA1500 power reduction
>
>Just my guess is one of the LDMOS devices let out the magic smoke?
>Just a thought...
>
>Dave wo2x
>
>
>-----Original Message-----
>From: [hidden email] <[hidden email]> On
>Behalf Of Dana Roode K6NR
>Sent: Saturday, February 20, 2021 9:16 PM
>To: Elecraft Reflector <[hidden email]>
>Subject: [Elecraft] Sudden KpA1500 power reduction
>
>I'm in the ARRL CW contest this weekend and the KPA1500 has been working
>fine. However, a few minutes ago I noticed I was getting about half the
>output power on 20 meters that I typically get with around 30 watts drive
>(about 600w vs 1200w). PA current is less than normal, around 30a.
>Similar problem on the higher bands, I can no longer get 1000w. On 40m I
>can, but it requires more drive.
>
>Seems like something died in the amp; I'm not familiar with the design, but
>perhaps an output module. No errors or ill behavior from the amp other than
>the loss of power.
>
>I will contact Elecraft support unless there is something I'm missing here.
>I just looked in the archive and see that this has happened to others.... I
>use the amp remotely so I guess I'll have to take it home with me.
>
> Dana
>______________________________________________________________
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Roy Koeppe

Sudden KPA1500 power reduction

Ditto here -- mine's at the factory.

73, Roy, K6XK

On 2/21/2021 11:32 AM, Frank Scolaro wrote:
> Happened to me several months ago... one LDMOS out! same symptoms. You need the power with such great band conditions...
>
> GL
> Frank, W2YK
>
>
>

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Wes Stewart-2

Re: Sudden KPA1500 power reduction

If I want more than my KPA500 puts out, I'm going back to tubes.

Wes N7WS

On 2/21/2021 10:47 AM, Roy wrote:
> Ditto here -- mine's at the factory.
>
> 73, Roy, K6XK

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Charlie T, K3ICH

Re: Sudden KPA1500 power reduction

In reply to this post by Roy Koeppe

Just curious, does the big FLEX amp use the same two LDMOS devices?
2nd question, have they shipped any yet? (probably not the right place to ask)

73, Charlie k3ICH

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of Roy
Sent: Sunday, February 21, 2021 12:47 PM
To: [hidden email]
Subject: [Elecraft] Sudden KPA1500 power reduction

Ditto here -- mine's at the factory.

73, Roy, K6XK

On 2/21/2021 11:32 AM, Frank Scolaro wrote:
> Happened to me several months ago... one LDMOS out! same symptoms. You need the power with such great band conditions...
>
> GL
> Frank, W2YK
>
>
>

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Dana Roode

Re: Sudden KpA1500 power reduction

In reply to this post by Frank Scolaro

Ok thanks everyone, I will lug the amp back home and contact Elecraft. Ive
had it for about 2 years, everything breaks now and again. I've got my
AL1200 here, I could use it at least when I'm here locally. I can't count
how many times I repaired that amp. But the KPA is above my skill level.

Dana

On Sun, Feb 21, 2021 at 9:32 AM Frank Scolaro <[hidden email]>
wrote:

>
> Happened to me several months ago... one LDMOS out! same symptoms. You
> need the power with such great band conditions...
>
> GL
> Frank, W2YK
>
>
>
>
> -----Original Message-----
> >From: [hidden email]
> >Sent: Feb 21, 2021 12:23 PM
> >To: 'Dana Roode K6NR' <[hidden email]>, 'Elecraft Reflector' <
> [hidden email]>
> >Subject: Re: [Elecraft] Sudden KpA1500 power reduction
> >
> >Just my guess is one of the LDMOS devices let out the magic smoke?
> >Just a thought...
> >
> >Dave wo2x
> >
> >
> >-----Original Message-----
> >From: [hidden email] <[hidden email]>
> On
> >Behalf Of Dana Roode K6NR
> >Sent: Saturday, February 20, 2021 9:16 PM
> >To: Elecraft Reflector <[hidden email]>
> >Subject: [Elecraft] Sudden KpA1500 power reduction
> >
> >I'm in the ARRL CW contest this weekend and the KPA1500 has been working
> >fine. However, a few minutes ago I noticed I was getting about half the
> >output power on 20 meters that I typically get with around 30 watts drive
> >(about 600w vs 1200w). PA current is less than normal, around 30a.
> >Similar problem on the higher bands, I can no longer get 1000w. On 40m I
> >can, but it requires more drive.
> >
> >Seems like something died in the amp; I'm not familiar with the design,
> but
> >perhaps an output module. No errors or ill behavior from the amp other
> than
> >the loss of power.
> >
> >I will contact Elecraft support unless there is something I'm missing
> here.
> >I just looked in the archive and see that this has happened to
> others.... I
> >use the amp remotely so I guess I'll have to take it home with me.
> >
> > Dana
> >______________________________________________________________
> >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]
> >
> >______________________________________________________________
> >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]
>

Dave wo2x

Re: Sudden KpA1500 power reduction

I will say the Rene at Elecraft was excellent when I sent my amp RF deck back for updates over a year ago. There were several updates that were performed while it was visiting the left coast. Elecraft support and repair is excellent.

The LDMOS devices in my KPa1500 are soldered to the copper heat spreader. Even though I have a Bertha soldering iron I would not attempt to change them myself.

73 & Good luck,
Dave wo2x

Sent from my waxed string and tin cans.

> On Feb 21, 2021, at 2:00 PM, Dana Roode K6NR <[hidden email]> wrote:
>
>
> Ok thanks everyone, I will lug the amp back home and contact Elecraft. Ive had it for about 2 years, everything breaks now and again. I've got my AL1200 here, I could use it at least when I'm here locally. I can't count how many times I repaired that amp. But the KPA is above my skill level.
>
> Dana
>
>
>> On Sun, Feb 21, 2021 at 9:32 AM Frank Scolaro <[hidden email]> wrote:
>>
>> Happened to me several months ago... one LDMOS out! same symptoms. You need the power with such great band conditions...
>>
>> GL
>> Frank, W2YK
>>
>>
>>
>>
>> -----Original Message-----
>> >From: [hidden email]
>> >Sent: Feb 21, 2021 12:23 PM
>> >To: 'Dana Roode K6NR' <[hidden email]>, 'Elecraft Reflector' <[hidden email]>
>> >Subject: Re: [Elecraft] Sudden KpA1500 power reduction
>> >
>> >Just my guess is one of the LDMOS devices let out the magic smoke?
>> >Just a thought...
>> >
>> >Dave wo2x
>> >
>> >
>> >-----Original Message-----
>> >From: [hidden email] <[hidden email]> On
>> >Behalf Of Dana Roode K6NR
>> >Sent: Saturday, February 20, 2021 9:16 PM
>> >To: Elecraft Reflector <[hidden email]>
>> >Subject: [Elecraft] Sudden KpA1500 power reduction
>> >
>> >I'm in the ARRL CW contest this weekend and the KPA1500 has been working
>> >fine. However, a few minutes ago I noticed I was getting about half the
>> >output power on 20 meters that I typically get with around 30 watts drive
>> >(about 600w vs 1200w). PA current is less than normal, around 30a.
>> >Similar problem on the higher bands, I can no longer get 1000w. On 40m I
>> >can, but it requires more drive.
>> >
>> >Seems like something died in the amp; I'm not familiar with the design, but
>> >perhaps an output module. No errors or ill behavior from the amp other than
>> >the loss of power.
>> >
>> >I will contact Elecraft support unless there is something I'm missing here.
>> >I just looked in the archive and see that this has happened to others.... I
>> >use the amp remotely so I guess I'll have to take it home with me.
>> >
>> > Dana
>> >______________________________________________________________
>> >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]
>> >
>> >______________________________________________________________
>> >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]

k6mrmagnet

Re: Sudden KpA1500 power reduction

In reply to this post by Dana Roode

It wouldn’t be above your skill level if they would release the schematics. Solid state amps are not any more complicated than tube amps, and I think easier (and safer!) than tubes. My early KPA1500 (#76) has been great, but not having the schematics really bugs me. I know everyone at Space Galactic Headquarters is busy with the K4 but posting the KPA1500 schematics would not take more than a few minutes. And my amp is way out of warranty so they aren’t risking anything. Internally it looks like a pretty generic design. I’ve reverse engineered the power supply unit but the RF deck is going to take some time. I’d rather not if I don’t have to.

Ken K6MR

From: Dana Roode K6NR<mailto:[hidden email]>
Sent: Sunday, February 21, 2021 11:03
To: Frank Scolaro<mailto:[hidden email]>
Cc: Elecraft Reflector<mailto:[hidden email]>
Subject: Re: [Elecraft] Sudden KpA1500 power reduction

Ok thanks everyone, I will lug the amp back home and contact Elecraft. Ive
had it for about 2 years, everything breaks now and again. I've got my
AL1200 here, I could use it at least when I'm here locally. I can't count
how many times I repaired that amp. But the KPA is above my skill level.

Dana

On Sun, Feb 21, 2021 at 9:32 AM Frank Scolaro <[hidden email]>
wrote:

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k6mrmagnet

Re: Sudden KpA1500 power reduction

In reply to this post by Dave wo2x

Replacing the LDMOS devices is not that difficult. Take a look at W6PQL’s site, he has a video on how to do it. http://www.w6pql.com/video/ldmos2copper.wmv

There also seems to be a dearth of information on the upgrades. I was also told that some upgrades are “factory only”. I don’t think they’ve ever done that before.

Ken K6MR

From: Dave<mailto:[hidden email]>
Sent: Sunday, February 21, 2021 11:06
To: Dana Roode K6NR<mailto:[hidden email]>
Cc: Elecraft Reflector<mailto:[hidden email]>
Subject: Re: [Elecraft] Sudden KpA1500 power reduction

I will say the Rene at Elecraft was excellent when I sent my amp RF deck back for updates over a year ago. There were several updates that were performed while it was visiting the left coast. Elecraft support and repair is excellent.

The LDMOS devices in my KPa1500 are soldered to the copper heat spreader. Even though I have a Bertha soldering iron I would not attempt to change them myself.

73 & Good luck,
Dave wo2x

Sent from my waxed string and tin cans.

Dr. William J. Schmidt, II

FW: Sudden KpA1500 power reduction

In reply to this post by k6mrmagnet

I've had the KPA1500 at my contest station in the Caribbean go south on me
(and another contest group) twice. Both times I was able to get Rene on the
phone.. go through the amp... and troubleshoot it over the phone. They have
always shared parts of the schematic with me when necessary. It's nothing
secret... just not publically posted.

Big shout out to Rene at Elecraft... Excellent tech.

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Ken K6MR
Sent: Sunday, February 21, 2021 1:11 PM
To: Dana Roode K6NR <[hidden email]>
Cc: Elecraft Reflector <[hidden email]>
Subject: Re: [Elecraft] Sudden KpA1500 power reduction

It wouldn't be above your skill level if they would release the schematics.
Solid state amps are not any more complicated than tube amps, and I think
easier (and safer!) than tubes. My early KPA1500 (#76) has been great, but
not having the schematics really bugs me. I know everyone at Space Galactic
Headquarters is busy with the K4 but posting the KPA1500 schematics would
not take more than a few minutes. And my amp is way out of warranty so they
aren't risking anything. Internally it looks like a pretty generic design.
I've reverse engineered the power supply unit but the RF deck is going to
take some time. I'd rather not if I don't have to.

Ken K6MR

--
This email has been checked for viruses by AVG.
https://www.avg.com

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k6mrmagnet

Re: FW: Sudden KpA1500 power reduction

“just not publically posted.”

Which seems very strange since they post for all the radios, which are far more complex. When I asked about a schematic, I was told “No”. Same with some updates.

Just seems strange.

Ken K6MR

From: Dr. William J. Schmidt<mailto:[hidden email]>
Sent: Sunday, February 21, 2021 12:04
To: [hidden email]<mailto:[hidden email]>
Subject: [Elecraft] FW: Sudden KpA1500 power reduction

I've had the KPA1500 at my contest station in the Caribbean go south on me
(and another contest group) twice. Both times I was able to get Rene on the
phone.. go through the amp... and troubleshoot it over the phone. They have
always shared parts of the schematic with me when necessary. It's nothing
secret... just not publically posted.

Big shout out to Rene at Elecraft... Excellent tech.

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Ken K6MR
Sent: Sunday, February 21, 2021 1:11 PM
To: Dana Roode K6NR <[hidden email]>
Cc: Elecraft Reflector <[hidden email]>
Subject: Re: [Elecraft] Sudden KpA1500 power reduction

It wouldn't be above your skill level if they would release the schematics.
Solid state amps are not any more complicated than tube amps, and I think
easier (and safer!) than tubes. My early KPA1500 (#76) has been great, but
not having the schematics really bugs me. I know everyone at Space Galactic
Headquarters is busy with the K4 but posting the KPA1500 schematics would
not take more than a few minutes. And my amp is way out of warranty so they
aren't risking anything. Internally it looks like a pretty generic design.
I've reverse engineered the power supply unit but the RF deck is going to
take some time. I'd rather not if I don't have to.

Ken K6MR

--
This email has been checked for viruses by AVG.
https://www.avg.com

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Dave wo2x

Re: Sudden KPA1500 power reduction

In reply to this post by Charlie T, K3ICH

1. Depends. My KPA1500 has same NXP 1K50H devices as my PG-XL. (yes, I have
both). I heard some KPA1500s had different devices than the NXP but cannot
confirm that

2. Yes. Shipping for a while now.

Here's my comparison of the two since I own both. The KPA1500 fan noise is
better to my ears sitting on the desk 4 feet from my operating position that
the PG-XL. I use the 1500 at home while the PG-XL due to its LAN integration
to the Flex radio is at the remote site 20 miles away.

Both are great amps and with the last updates done to my KPA1500 a little
over a year ago it has been trouble free.

Dave wo2x

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Charlie T
Sent: Sunday, February 21, 2021 1:31 PM
To: [hidden email]
Subject: Re: [Elecraft] Sudden KPA1500 power reduction

Just curious, does the big FLEX amp use the same two LDMOS devices?
2nd question, have they shipped any yet? (probably not the right place to
ask)

73, Charlie k3ICH

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Roy
Sent: Sunday, February 21, 2021 12:47 PM
To: [hidden email]
Subject: [Elecraft] Sudden KPA1500 power reduction

Ditto here -- mine's at the factory.

73, Roy, K6XK

On 2/21/2021 11:32 AM, Frank Scolaro wrote:
> Happened to me several months ago... one LDMOS out! same symptoms. You
need the power with such great band conditions...
>
> GL
> Frank, W2YK
>
>
>

______________________________________________________________
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