Topics

KPA500 No Power Output


Jeff Clarke KU8E
 

I'm having a problem with my KPA500. I'm using it with a K3-100 and keying the amp with KPAK3AUX cable. Here are the symptoms:

1) No Power output from amplifier. The K3-100 is OK.

2) When I transmit in standby the SWR is OK but when I switch to OPER the SWR is infinite. I tested this on both my antenna and a dummy load.

3) Did the power supply voltage test. HV reads 72.8 volts which it looks like in the manual is in the normal range.

4) Current reads .0    I believe this isn't normal ?

5) I checked the fuse block and both fuses seem to be OK.

I was operating FT8 and heard a pop from the amplifier. I've sent an email to Elecraft support but I was just wondering if anyone else has had this happen? My assumption is some component inside the amp has blown and I'm going to have to send it in for service.  I've had this amp for awhile and this is the first time I've had any problem with it.

Jeff KU8E


redarlington <rdarlington@...>
 

Is there anything rattling around loose inside?  This happened very recently to our club's KPA500 and Elecraft and I were pretty convinced the finals let out the magic smoke.  I opened it up and found a diode very cleanly desoldered laying inside.  Easy fix, just solder it back in and don't do whatever it is you were doing again (like run FT8 at high power).    I learned from this.   Even with the fans up, some bits get hot faster than others!  And "just solder it back" doesn't really convey the real pain in the butt it was to do it.  The diode was no the filter board, as deep as you can get inside the thing.

-Bob N3XKB

On Fri, Apr 3, 2020 at 2:24 PM Jeff Clarke <ku8e@...> wrote:
I'm having a problem with my KPA500. I'm using it with a K3-100 and keying the amp with KPAK3AUX cable. Here are the symptoms:

1) No Power output from amplifier. The K3-100 is OK.

2) When I transmit in standby the SWR is OK but when I switch to OPER the SWR is infinite. I tested this on both my antenna and a dummy load.

3) Did the power supply voltage test. HV reads 72.8 volts which it looks like in the manual is in the normal range.

4) Current reads .0    I believe this isn't normal ?

5) I checked the fuse block and both fuses seem to be OK.

I was operating FT8 and heard a pop from the amplifier. I've sent an email to Elecraft support but I was just wondering if anyone else has had this happen? My assumption is some component inside the amp has blown and I'm going to have to send it in for service.  I've had this amp for awhile and this is the first time I've had any problem with it.

Jeff KU8E


Randy Farmer W8FN
 

Yikes! There's a known failure of the KPA500 that takes out the PIN diodes in the T/R switch, or at least disables them. There's also a factory fix. Hope that's not it, but it does sound possible.

73...
Randy, W8FN

On 4/3/2020 4:24 PM, Jeff Clarke wrote:
I'm having a problem with my KPA500. I'm using it with a K3-100 and keying the amp with KPAK3AUX cable. Here are the symptoms:

1) No Power output from amplifier. The K3-100 is OK.

2) When I transmit in standby the SWR is OK but when I switch to OPER the SWR is infinite. I tested this on both my antenna and a dummy load.

3) Did the power supply voltage test. HV reads 72.8 volts which it looks like in the manual is in the normal range.

4) Current reads .0    I believe this isn't normal ?

5) I checked the fuse block and both fuses seem to be OK.

I was operating FT8 and heard a pop from the amplifier. I've sent an email to Elecraft support but I was just wondering if anyone else has had this happen? My assumption is some component inside the amp has blown and I'm going to have to send it in for service.  I've had this amp for awhile and this is the first time I've had any problem with it.

Jeff KU8E


iain macdonnell - N6ML
 

I'd recommend caution when testing. My KPA500 had a T/R failure (magic
smoke escaped from seveal components) a while back. It's one of the
very early models, and didn't have some of the later enhancements to
the T/R components. When I was attempting to diagnose mine, I ended up
frying the "10w" finals in my K3 (by transmitting with RF level set
below 12w). I guess some RF was getting fed back from the KPA500, and
the KPA3 finals were able to handle it, but the low power ones were
not.

GL/73,

~iain / N6ML

On Fri, Apr 3, 2020 at 1:24 PM Jeff Clarke <ku8e@ku8e.com> wrote:

I'm having a problem with my KPA500. I'm using it with a K3-100 and keying the amp with KPAK3AUX cable. Here are the symptoms:

1) No Power output from amplifier. The K3-100 is OK.

2) When I transmit in standby the SWR is OK but when I switch to OPER the SWR is infinite. I tested this on both my antenna and a dummy load.

3) Did the power supply voltage test. HV reads 72.8 volts which it looks like in the manual is in the normal range.

4) Current reads .0 I believe this isn't normal ?

5) I checked the fuse block and both fuses seem to be OK.

I was operating FT8 and heard a pop from the amplifier. I've sent an email to Elecraft support but I was just wondering if anyone else has had this happen? My assumption is some component inside the amp has blown and I'm going to have to send it in for service. I've had this amp for awhile and this is the first time I've had any problem with it.

Jeff KU8E


Rick NK7I
 

If only on one band, tuned input circuit, $$ not awful. 

If all bands, the finals, $$ between ok and ouch. 

Don’t forget the shipping insurance, but on the plus side; it’ll get all the updates. 

Rick NK7I

Smell Czech corruptions are inevitable

On Apr 3, 2020, at 1:37 PM, Randy Farmer <w8fn@...> wrote:

 Yikes! There's a known failure of the KPA500 that takes out the PIN diodes in the T/R switch, or at least disables them. There's also a factory fix. Hope that's not it, but it does sound possible.

73...
Randy, W8FN

On 4/3/2020 4:24 PM, Jeff Clarke wrote:
I'm having a problem with my KPA500. I'm using it with a K3-100 and keying the amp with KPAK3AUX cable. Here are the symptoms:

1) No Power output from amplifier. The K3-100 is OK.

2) When I transmit in standby the SWR is OK but when I switch to OPER the SWR is infinite. I tested this on both my antenna and a dummy load.

3) Did the power supply voltage test. HV reads 72.8 volts which it looks like in the manual is in the normal range.

4) Current reads .0    I believe this isn't normal ?

5) I checked the fuse block and both fuses seem to be OK.

I was operating FT8 and heard a pop from the amplifier. I've sent an email to Elecraft support but I was just wondering if anyone else has had this happen? My assumption is some component inside the amp has blown and I'm going to have to send it in for service.  I've had this amp for awhile and this is the first time I've had any problem with it.

Jeff KU8E


john ni0k
 

Iain,

The issue is that the low power finals will not sustain steady transmit at that power level. Many have discovered this as you have. If you need that power level, use an attenuator (eBay) with the high power finals engaged (above 12W)

-de John NI0K

iain macdonnell - N6ML wrote on 4/3/2020 3:46 PM:

I'd recommend caution when testing. My KPA500 had a T/R failure (magic
smoke escaped from seveal components) a while back. It's one of the
very early models, and didn't have some of the later enhancements to
the T/R components. When I was attempting to diagnose mine, I ended up
frying the "10w" finals in my K3 (by transmitting with RF level set
below 12w). I guess some RF was getting fed back from the KPA500, and
the KPA3 finals were able to handle it, but the low power ones were
not.

GL/73,

~iain / N6ML



On Fri, Apr 3, 2020 at 1:24 PM Jeff Clarke <ku8e@ku8e.com> wrote:
I'm having a problem with my KPA500. I'm using it with a K3-100 and keying the amp with KPAK3AUX cable. Here are the symptoms:

1) No Power output from amplifier. The K3-100 is OK.

2) When I transmit in standby the SWR is OK but when I switch to OPER the SWR is infinite. I tested this on both my antenna and a dummy load.

3) Did the power supply voltage test. HV reads 72.8 volts which it looks like in the manual is in the normal range.

4) Current reads .0 I believe this isn't normal ?

5) I checked the fuse block and both fuses seem to be OK.

I was operating FT8 and heard a pop from the amplifier. I've sent an email to Elecraft support but I was just wondering if anyone else has had this happen? My assumption is some component inside the amp has blown and I'm going to have to send it in for service. I've had this amp for awhile and this is the first time I've had any problem with it.

Jeff KU8E


Christopher Scibelli
 

I'm very sorry this happened especially at this time. 

Let John's misfortune be a lesson to all who run amps or those running barefoot rigs and FT8.  Ordinarily, I'd keep my Alpha on for hours on end.  In the AM I do an hour or two of CW but with no amplifier.  When I run phone and am working Europe I'd normally run legal-limit power. Not now.  I reduced my power to a kW.  I pay more attention to the temperature of the Alpha.  I'm doing very little FT8.

I do have a backup amp and backup rigs but I'm being extra careful.

73,

Chris  NU1O



-----Original Message-----
From: john ni0k <jasimmons@...>
To: Elecraft-K3 <Elecraft-K3@groups.io>
Sent: Fri, Apr 3, 2020 4:51 pm
Subject: Re: [Elecraft-K3] KPA500 No Power Output

Iain,

The issue is that the low power finals will not sustain steady transmit
at that power level. Many have discovered this as you have. If you need
that power level, use an attenuator (eBay) with the high power finals
engaged (above 12W)

-de John NI0K

iain macdonnell - N6ML wrote on 4/3/2020 3:46 PM:
> I'd recommend caution when testing. My KPA500 had a T/R failure (magic
> smoke escaped from seveal components) a while back. It's one of the
> very early models, and didn't have some of the later enhancements to
> the T/R components. When I was attempting to diagnose mine, I ended up
> frying the "10w" finals in my K3 (by transmitting with RF level set
> below 12w). I guess some RF was getting fed back from the KPA500, and
> the KPA3 finals were able to handle it, but the low power ones were
> not.
>
> GL/73,
>
>      ~iain / N6ML
>
>
>
> On Fri, Apr 3, 2020 at 1:24 PM Jeff Clarke <ku8e@...> wrote:
>> I'm having a problem with my KPA500. I'm using it with a K3-100 and keying the amp with KPAK3AUX cable. Here are the symptoms:
>>
>> 1) No Power output from amplifier. The K3-100 is OK.
>>
>> 2) When I transmit in standby the SWR is OK but when I switch to OPER the SWR is infinite. I tested this on both my antenna and a dummy load.
>>
>> 3) Did the power supply voltage test. HV reads 72.8 volts which it looks like in the manual is in the normal range.
>>
>> 4) Current reads .0    I believe this isn't normal ?
>>
>> 5) I checked the fuse block and both fuses seem to be OK.
>>
>> I was operating FT8 and heard a pop from the amplifier. I've sent an email to Elecraft support but I was just wondering if anyone else has had this happen? My assumption is some component inside the amp has blown and I'm going to have to send it in for service.  I've had this amp for awhile and this is the first time I've had any problem with it.
>>
>> Jeff KU8E
>>
>
>





Robert W5AJ
 

ah, interesting

I run 10 watts out of my K3-100 all the time on FT8/JT65/RTTY feeding (non-Elecraft) afterburner

 

so this is a “Risky” mode??

 

73 W5AJ

 

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Christopher Scibelli via groups.io
Sent: Friday, April 03, 2020 4:19 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] KPA500 No Power Output

 

I'm very sorry this happened especially at this time. 

Let John's misfortune be a lesson to all who run amps or those running barefoot rigs and FT8.  Ordinarily, I'd keep my Alpha on for hours on end.  In the AM I do an hour or two of CW but with no amplifier.  When I run phone and am working Europe I'd normally run legal-limit power. Not now.  I reduced my power to a kW.  I pay more attention to the temperature of the Alpha.  I'm doing very little FT8.

I do have a backup amp and backup rigs but I'm being extra careful.

73,

Chris  NU1O



-----Original Message-----
From: john ni0k <jasimmons@...>
To: Elecraft-K3 <Elecraft-K3@groups.io>
Sent: Fri, Apr 3, 2020 4:51 pm
Subject: Re: [Elecraft-K3] KPA500 No Power Output

Iain,

The issue is that the low power finals will not sustain steady transmit
at that power level. Many have discovered this as you have. If you need
that power level, use an attenuator (eBay) with the high power finals
engaged (above 12W)

-de John NI0K

iain macdonnell - N6ML wrote on 4/3/2020 3:46 PM:
> I'd recommend caution when testing. My KPA500 had a T/R failure (magic
> smoke escaped from seveal components) a while back. It's one of the
> very early models, and didn't have some of the later enhancements to
> the T/R components. When I was attempting to diagnose mine, I ended up
> frying the "10w" finals in my K3 (by transmitting with RF level set
> below 12w). I guess some RF was getting fed back from the KPA500, and
> the KPA3 finals were able to handle it, but the low power ones were
> not.
>
> GL/73,
>
>      ~iain / N6ML
>
>
>
> On Fri, Apr 3, 2020 at 1:24 PM Jeff Clarke <ku8e@...> wrote:
>> I'm having a problem with my KPA500. I'm using it with a K3-100 and keying the amp with KPAK3AUX cable. Here are the symptoms:
>>
>> 1) No Power output from amplifier. The K3-100 is OK.
>>
>> 2) When I transmit in standby the SWR is OK but when I switch to OPER the SWR is infinite. I tested this on both my antenna and a dummy load.
>>
>> 3) Did the power supply voltage test. HV reads 72.8 volts which it looks like in the manual is in the normal range.
>>
>> 4) Current reads .0    I believe this isn't normal ?
>>
>> 5) I checked the fuse block and both fuses seem to be OK.
>>
>> I was operating FT8 and heard a pop from the amplifier. I've sent an email to Elecraft support but I was just wondering if anyone else has had this happen? My assumption is some component inside the amp has blown and I'm going to have to send it in for service.  I've had this amp for awhile and this is the first time I've had any problem with it.
>>
>> Jeff KU8E
>>
>
>




Stephen Walls
 

I had the exact thing happen.    

Step 1------totally unhook amp.

Step 2-----pick it up, and turn it upside down and see if anything rattles.

If it does,  the tops of the transistors have blown off.

You can pull the lid and shake them out,   I have both mine hanging in a Zip-Lock bag on the wall above the radios.     $100+ shipping out to west coast.

A bad KAT500 caused mine to fail-----both pieces fixed under warranty----tuner was another $30-40 shipping out there.

Good luck---

Steve  K4ELI



On Friday, April 3, 2020, 04:24:50 PM EDT, Jeff Clarke <ku8e@...> wrote:


I'm having a problem with my KPA500. I'm using it with a K3-100 and keying the amp with KPAK3AUX cable. Here are the symptoms:

1) No Power output from amplifier. The K3-100 is OK.

2) When I transmit in standby the SWR is OK but when I switch to OPER the SWR is infinite. I tested this on both my antenna and a dummy load.

3) Did the power supply voltage test. HV reads 72.8 volts which it looks like in the manual is in the normal range.

4) Current reads .0    I believe this isn't normal ?

5) I checked the fuse block and both fuses seem to be OK.

I was operating FT8 and heard a pop from the amplifier. I've sent an email to Elecraft support but I was just wondering if anyone else has had this happen? My assumption is some component inside the amp has blown and I'm going to have to send it in for service.  I've had this amp for awhile and this is the first time I've had any problem with it.

Jeff KU8E


redarlington <rdarlington@...>
 

$111 each from digikey with 2.5 hours of labor at $99/hr for elecraft to do it.  I opened my amp right before shipping and saw that it was not the finals at all.   Just a big diode that I soldered back in.    First step, find out what's rattling and go from there -assuming anything is rattling.

-Bob N3XKB

On Fri, Apr 3, 2020, 4:21 PM Stephen Walls <swalls46@...> wrote:
I had the exact thing happen.    

Step 1------totally unhook amp.

Step 2-----pick it up, and turn it upside down and see if anything rattles.

If it does,  the tops of the transistors have blown off.

You can pull the lid and shake them out,   I have both mine hanging in a Zip-Lock bag on the wall above the radios.     $100+ shipping out to west coast.

A bad KAT500 caused mine to fail-----both pieces fixed under warranty----tuner was another $30-40 shipping out there.

Good luck---

Steve  K4ELI



On Friday, April 3, 2020, 04:24:50 PM EDT, Jeff Clarke <ku8e@...> wrote:


I'm having a problem with my KPA500. I'm using it with a K3-100 and keying the amp with KPAK3AUX cable. Here are the symptoms:

1) No Power output from amplifier. The K3-100 is OK.

2) When I transmit in standby the SWR is OK but when I switch to OPER the SWR is infinite. I tested this on both my antenna and a dummy load.

3) Did the power supply voltage test. HV reads 72.8 volts which it looks like in the manual is in the normal range.

4) Current reads .0    I believe this isn't normal ?

5) I checked the fuse block and both fuses seem to be OK.

I was operating FT8 and heard a pop from the amplifier. I've sent an email to Elecraft support but I was just wondering if anyone else has had this happen? My assumption is some component inside the amp has blown and I'm going to have to send it in for service.  I've had this amp for awhile and this is the first time I've had any problem with it.

Jeff KU8E


Christopher Scibelli
 

Based on what I read from Elecraft, I assumed only those on the design team for the K4 are still working.  Logistically, I'd think it would be difficult to repair rigs from home.  I doubt all those techs have the needed equipment at home so I would think if it has to go back to Elecraft it's going to be a long wait.

73,

Chris  NU1O



-----Original Message-----
From: redarlington <rdarlington@...>
To: Elecraft-K3 <Elecraft-K3@groups.io>
Sent: Fri, Apr 3, 2020 7:18 pm
Subject: Re: [Elecraft-K3] KPA500 No Power Output

$111 each from digikey with 2.5 hours of labor at $99/hr for elecraft to do it.  I opened my amp right before shipping and saw that it was not the finals at all.   Just a big diode that I soldered back in.    First step, find out what's rattling and go from there -assuming anything is rattling.

-Bob N3XKB

On Fri, Apr 3, 2020, 4:21 PM Stephen Walls <swalls46@...> wrote:
I had the exact thing happen.    

Step 1------totally unhook amp.

Step 2-----pick it up, and turn it upside down and see if anything rattles.

If it does,  the tops of the transistors have blown off.

You can pull the lid and shake them out,   I have both mine hanging in a Zip-Lock bag on the wall above the radios.     $100+ shipping out to west coast.

A bad KAT500 caused mine to fail-----both pieces fixed under warranty----tuner was another $30-40 shipping out there.

Good luck---

Steve  K4ELI



On Friday, April 3, 2020, 04:24:50 PM EDT, Jeff Clarke <ku8e@...> wrote:


I'm having a problem with my KPA500. I'm using it with a K3-100 and keying the amp with KPAK3AUX cable. Here are the symptoms:

1) No Power output from amplifier. The K3-100 is OK.

2) When I transmit in standby the SWR is OK but when I switch to OPER the SWR is infinite. I tested this on both my antenna and a dummy load.

3) Did the power supply voltage test. HV reads 72.8 volts which it looks like in the manual is in the normal range.

4) Current reads .0    I believe this isn't normal ?

5) I checked the fuse block and both fuses seem to be OK.

I was operating FT8 and heard a pop from the amplifier. I've sent an email to Elecraft support but I was just wondering if anyone else has had this happen? My assumption is some component inside the amp has blown and I'm going to have to send it in for service.  I've had this amp for awhile and this is the first time I've had any problem with it.

Jeff KU8E


Jeff Clarke KU8E
 

I've owned this amp for maybe 5 years and this is the first time I've had an issue. I was only running about 300 watts on FT8. When I use it in a contest I am very conservative and run 500 watts max.If you have a flat SWR on your antenna you can get it up to around 700 watts if you want. BTW this problem is occurring on all the bands. I'm thinking it's some kind of T/R relay failure because the way the SWR is acting when you put it in OPER. It's reading "--" and then jumps back and forth to 99:1. In standby it's just fine. 

It's been a real pain that the KPA500 always trips when you get near a 2:1 SWR and you have to reset it all the time. I've been thinking about buying another amp for awhile because of that. I ordered an Acom 1000 today. That will be my main amp with the KPA500 as a backup after I get it repaired. That might be awhile before I can get the KPA500 repaired because the reply I got from Elecraft says they aren't doing RSA's right now because of COVID-19.

Jeff


Christopher Scibelli
 

I've had tube amps for the 30+ years I've been a ham.  I own an Alpha 8410 and a Heathkit SB-1000.  I built the Heathkit back in 1988 and it works like it is new.  Pretty sure it's the same as an Al-80B by Ameritron. I wouldn't want to buy it from MFJ but the design is solid.  The ham who designed it is very well known but I'm too tired to recall his call.  Pretty sure somebody in this forum knows who I'm referring to.

Best of luck and 73,

Chris  NU1O


-----Original Message-----
From: Jeff Clarke <ku8e@...>
To: Elecraft-K3 <Elecraft-K3@groups.io>
Sent: Fri, Apr 3, 2020 8:48 pm
Subject: Re: [Elecraft-K3] KPA500 No Power Output

I've owned this amp for maybe 5 years and this is the first time I've had an issue. I was only running about 300 watts on FT8. When I use it in a contest I am very conservative and run 500 watts max.If you have a flat SWR on your antenna you can get it up to around 700 watts if you want. BTW this problem is occurring on all the bands. I'm thinking it's some kind of T/R relay failure because the way the SWR is acting when you put it in OPER. It's reading "--" and then jumps back and forth to 99:1. In standby it's just fine. 

It's been a real pain that the KPA500 always trips when you get near a 2:1 SWR and you have to reset it all the time. I've been thinking about buying another amp for awhile because of that. I ordered an Acom 1000 today. That will be my main amp with the KPA500 as a backup after I get it repaired. That might be awhile before I can get the KPA500 repaired because the reply I got from Elecraft says they aren't doing RSA's right now because of COVID-19.

Jeff


Richard Smith
 

Love my Acom 1000.  I keep  K3S at 35 watts, giving me @650 out on amp.   I never run max.  RAS KU4NZ


On Apr 3, 2020, at 8:06 PM, Christopher Scibelli via groups.io <nu1oscar@...> wrote:

I've had tube amps for the 30+ years I've been a ham.  I own an Alpha 8410 and a Heathkit SB-1000.  I built the Heathkit back in 1988 and it works like it is new.  Pretty sure it's the same as an Al-80B by Ameritron. I wouldn't want to buy it from MFJ but the design is solid.  The ham who designed it is very well known but I'm too tired to recall his call.  Pretty sure somebody in this forum knows who I'm referring to.

Best of luck and 73,

Chris  NU1O


-----Original Message-----
From: Jeff Clarke <ku8e@...>
To: Elecraft-K3 <Elecraft-K3@groups.io>
Sent: Fri, Apr 3, 2020 8:48 pm
Subject: Re: [Elecraft-K3] KPA500 No Power Output

I've owned this amp for maybe 5 years and this is the first time I've had an issue. I was only running about 300 watts on FT8. When I use it in a contest I am very conservative and run 500 watts max.If you have a flat SWR on your antenna you can get it up to around 700 watts if you want. BTW this problem is occurring on all the bands. I'm thinking it's some kind of T/R relay failure because the way the SWR is acting when you put it in OPER. It's reading "--" and then jumps back and forth to 99:1. In standby it's just fine. 

It's been a real pain that the KPA500 always trips when you get near a 2:1 SWR and you have to reset it all the time. I've been thinking about buying another amp for awhile because of that. I ordered an Acom 1000 today. That will be my main amp with the KPA500 as a backup after I get it repaired. That might be awhile before I can get the KPA500 repaired because the reply I got from Elecraft says they aren't doing RSA's right now because of COVID-19.

Jeff


Bill K9YEQ
 

I love my KPA1500 and drive it with 22-28 watts at 1500 out.  Works perfectly with K3S and remote antenna switch and tuner.  No issues for several years.  Great reliability.

 

Bill

K9YEQ

 

From: Elecraft-K3@groups.io <Elecraft-K3@groups.io> On Behalf Of Richard Smith
Sent: Friday, April 3, 2020 8:21 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] KPA500 No Power Output

 

Love my Acom 1000.  I keep  K3S at 35 watts, giving me @650 out on amp.   I never run max.  RAS KU4NZ

 



On Apr 3, 2020, at 8:06 PM, Christopher Scibelli via groups.io <nu1oscar@...> wrote:

 

I've had tube amps for the 30+ years I've been a ham.  I own an Alpha 8410 and a Heathkit SB-1000.  I built the Heathkit back in 1988 and it works like it is new.  Pretty sure it's the same as an Al-80B by Ameritron. I wouldn't want to buy it from MFJ but the design is solid.  The ham who designed it is very well known but I'm too tired to recall his call.  Pretty sure somebody in this forum knows who I'm referring to.

Best of luck and 73,

Chris  NU1O


-----Original Message-----
From: Jeff Clarke <ku8e@...>
To: Elecraft-K3 <Elecraft-K3@groups.io>
Sent: Fri, Apr 3, 2020 8:48 pm
Subject: Re: [Elecraft-K3] KPA500 No Power Output

I've owned this amp for maybe 5 years and this is the first time I've had an issue. I was only running about 300 watts on FT8. When I use it in a contest I am very conservative and run 500 watts max.If you have a flat SWR on your antenna you can get it up to around 700 watts if you want. BTW this problem is occurring on all the bands. I'm thinking it's some kind of T/R relay failure because the way the SWR is acting when you put it in OPER. It's reading "--" and then jumps back and forth to 99:1. In standby it's just fine. 

It's been a real pain that the KPA500 always trips when you get near a 2:1 SWR and you have to reset it all the time. I've been thinking about buying another amp for awhile because of that. I ordered an Acom 1000 today. That will be my main amp with the KPA500 as a backup after I get it repaired. That might be awhile before I can get the KPA500 repaired because the reply I got from Elecraft says they aren't doing RSA's right now because of COVID-19.

Jeff

 


Bob McGraw - K4TAX
 

If one is running 500 watts and think that is conservative and find they can get 700 watts out on a flat antenna, then I would expect it’d amp to fail. It is a 500 watts max amp!

Bob, K4TAX


Charlie T, k3ICH
 

The Heath SB-1000 is the same as an AL-80A, but NOT the same is the improved AL-80B

 

Charlie k3ICH

 

 

 

 

From: Elecraft-K3@groups.io <Elecraft-K3@groups.io> On Behalf Of Christopher Scibelli via groups.io
Sent: Friday, April 03, 2020 9:06 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] KPA500 No Power Output

 

I've had tube amps for the 30+ years I've been a ham.  I own an Alpha 8410 and a Heathkit SB-1000.  I built the Heathkit back in 1988 and it works like it is new.  Pretty sure it's the same as an Al-80B by Ameritron. I wouldn't want to buy it from MFJ but the design is solid.  The ham who designed it is very well known but I'm too tired to recall his call.  Pretty sure somebody in this forum knows who I'm referring to.

Best of luck and 73,

Chris  NU1O


-----Original Message-----
From: Jeff Clarke <ku8e@...>
To: Elecraft-K3 <Elecraft-K3@groups.io>
Sent: Fri, Apr 3, 2020 8:48 pm
Subject: Re: [Elecraft-K3] KPA500 No Power Output

I've owned this amp for maybe 5 years and this is the first time I've had an issue. I was only running about 300 watts on FT8. When I use it in a contest I am very conservative and run 500 watts max.If you have a flat SWR on your antenna you can get it up to around 700 watts if you want. BTW this problem is occurring on all the bands. I'm thinking it's some kind of T/R relay failure because the way the SWR is acting when you put it in OPER. It's reading "--" and then jumps back and forth to 99:1. In standby it's just fine. 

It's been a real pain that the KPA500 always trips when you get near a 2:1 SWR and you have to reset it all the time. I've been thinking about buying another amp for awhile because of that. I ordered an Acom 1000 today. That will be my main amp with the KPA500 as a backup after I get it repaired. That might be awhile before I can get the KPA500 repaired because the reply I got from Elecraft says they aren't doing RSA's right now because of COVID-19.

Jeff


 

I had this one years ago.
Found the fault in the T/R circuitry myself and then heard about the Mod that Elecraft had for this problem after sending an email to Elecraft.
Ordered the Mod, did the repair on 3 May 2015 (I keep track of that), and presto, problem solved.

The mod is called: Elecraft Parts Kit E850607
Manual that came with it is called: KPA LPF T/R Switch Rework Instructions (applicable to Low Pass Filter Board, partnumber E850406, rev D9 or earlier)
Date of manual: December 24, 2013, rev E

With this mod, the LPF board became a Rev D10.


Hope this helps.

73 to all from the Netherlands, EU

Arie PA3A



Op 3-4-2020 om 22:37 schreef Randy Farmer:

Yikes! There's a known failure of the KPA500 that takes out the PIN diodes in the T/R switch, or at least disables them. There's also a factory fix. Hope that's not it, but it does sound possible.

73...
Randy, W8FN
_._,_._,_


Christopher Scibelli
 

Had a feeling that was the case, but since I don't own one I deferred to an owner.

NU1O


-----Original Message-----
From: Bob McGraw - K4TAX <rmcgraw@...>
To: Elecraft-K3 <Elecraft-K3@groups.io>
Sent: Fri, Apr 3, 2020 11:11 pm
Subject: Re: [Elecraft-K3] KPA500 No Power Output

If one is running 500 watts and think that is conservative and find they can get 700 watts out on a flat antenna, then I would expect it’d amp to fail.  It is a 500 watts max amp!

Bob, K4TAX



Christopher Scibelli
 

Thank you for the clarification.

73,

Chris  NU1O


-----Original Message-----
From: Charlie T, k3ICH <pincon@...>
To: Elecraft-K3 <Elecraft-K3@groups.io>
Sent: Fri, Apr 3, 2020 11:22 pm
Subject: Re: [Elecraft-K3] KPA500 No Power Output

The Heath SB-1000 is the same as an AL-80A, but NOT the same is the improved AL-80B

 

Charlie k3ICH

 

 

 

 

From: Elecraft-K3@groups.io <Elecraft-K3@groups.io> On Behalf Of Christopher Scibelli via groups.io
Sent: Friday, April 03, 2020 9:06 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] KPA500 No Power Output

 

I've had tube amps for the 30+ years I've been a ham.  I own an Alpha 8410 and a Heathkit SB-1000.  I built the Heathkit back in 1988 and it works like it is new.  Pretty sure it's the same as an Al-80B by Ameritron. I wouldn't want to buy it from MFJ but the design is solid.  The ham who designed it is very well known but I'm too tired to recall his call.  Pretty sure somebody in this forum knows who I'm referring to.

Best of luck and 73,

Chris  NU1O


-----Original Message-----
From: Jeff Clarke <ku8e@...>
To: Elecraft-K3 <Elecraft-K3@groups.io>
Sent: Fri, Apr 3, 2020 8:48 pm
Subject: Re: [Elecraft-K3] KPA500 No Power Output

I've owned this amp for maybe 5 years and this is the first time I've had an issue. I was only running about 300 watts on FT8. When I use it in a contest I am very conservative and run 500 watts max.If you have a flat SWR on your antenna you can get it up to around 700 watts if you want. BTW this problem is occurring on all the bands. I'm thinking it's some kind of T/R relay failure because the way the SWR is acting when you put it in OPER. It's reading "--" and then jumps back and forth to 99:1. In standby it's just fine. 

It's been a real pain that the KPA500 always trips when you get near a 2:1 SWR and you have to reset it all the time. I've been thinking about buying another amp for awhile because of that. I ordered an Acom 1000 today. That will be my main amp with the KPA500 as a backup after I get it repaired. That might be awhile before I can get the KPA500 repaired because the reply I got from Elecraft says they aren't doing RSA's right now because of COVID-19.

Jeff