[Elecraft] Sudden KpA1500 power reduction

[Ken K6MR]

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:rocketnj at gmail.com>
Sent: Sunday, February 21, 2021 11:06
To: Dana Roode K6NR<mailto:dana.roode at gmail.com>
Cc: Elecraft Reflector<mailto:Elecraft at mailman.qth.net>
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.

> On Feb 21, 2021, at 2:00 PM, Dana Roode K6NR <dana.roode at gmail.com> 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 <fscolaro at mindspring.com> 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: rocketnj at gmail.com
>> >Sent: Feb 21, 2021 12:23 PM
>> >To: 'Dana Roode K6NR' <dana.roode at gmail.com>, 'Elecraft Reflector' <Elecraft at mailman.qth.net>
>> >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: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On
>> >Behalf Of Dana Roode K6NR
>> >Sent: Saturday, February 20, 2021 9:16 PM
>> >To: Elecraft Reflector <Elecraft at mailman.qth.net>
>> >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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>> >
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