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KPA500 Problem

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k4vd

KPA500 Problem

Waiting on an answer from Elecraft but thought I'd also check with the
group here.

I have a Flex 6500 with KAT500/KPA500 combo. It's been working great until
very recently. Within the past couple of days I was intermittently reading
high SWR when the amp is in operate. In standby or off everything looks
good. As of last night it's not so intermittent.

In receive when I switch from standby to operate I'm only receiving the
strongest of signals. Everything else disappears almost like the antenna
was disconnected.

When switching between standby and operate I hear a relay clicking. I'm not
sure but it doesn't seem to be as loud a click as I normally hear but I
can't be sure.

With the amp powered down and the Flex set to 100 watts out everything
seems to be working fine. I'm afraid my amp is going to take a trip. Any
ideas for things to check?

73,
Kev K4VD
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Don Wilhelm

Re: KPA500 Problem

Kev,

That behavior can be caused by a coax jumper, either loose or faulty in
some way. Make sure the PL-259s are tight and if you can substitute the
jumpers with known good ones - particularly the one between the KPA500
and the KAT500 and the one between your transceiver and the KPA500.
There are as many problems caused by cables as are caused by equipment.
Some cable problems have no apparent problem at lower power, but rear
their ugly head at higher power.
You could also have a higher power problem with your antenna. Switch to
an alternate antenna or dummy load if possible (tune the KAT500 into the
dummy load) as a test.

73,
Don W3FPR

On 11/13/2017 4:41 PM, Kevin der Kinderen wrote:

> Waiting on an answer from Elecraft but thought I'd also check with the
> group here.
>
> I have a Flex 6500 with KAT500/KPA500 combo. It's been working great until
> very recently. Within the past couple of days I was intermittently reading
> high SWR when the amp is in operate. In standby or off everything looks
> good. As of last night it's not so intermittent.
>
> In receive when I switch from standby to operate I'm only receiving the
> strongest of signals. Everything else disappears almost like the antenna
> was disconnected.
>
> When switching between standby and operate I hear a relay clicking. I'm not
> sure but it doesn't seem to be as loud a click as I normally hear but I
> can't be sure.
>
> With the amp powered down and the Flex set to 100 watts out everything
> seems to be working fine. I'm afraid my amp is going to take a trip. Any
> ideas for things to check?
>
> 73,
> Kev K4VD
> ______________________________________________________________
> 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]
>

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Michael Walker

Re: KPA500 Problem

Hi Kev

Don is 100% right.

I would change all the cables and then test with the amp alone and the
tuner alone to narrow it down.

I spent 3 days debugging an Acom A1000 issue only to finally out I had a
bad jumper cable.

Mike va3mw

On Mon, Nov 13, 2017 at 5:05 PM, Don Wilhelm <[hidden email]> wrote:

> Kev,
>
> That behavior can be caused by a coax jumper, either loose or faulty in
> some way. Make sure the PL-259s are tight and if you can substitute the
> jumpers with known good ones - particularly the one between the KPA500 and
> the KAT500 and the one between your transceiver and the KPA500.
> There are as many problems caused by cables as are caused by equipment.
> Some cable problems have no apparent problem at lower power, but rear
> their ugly head at higher power.
> You could also have a higher power problem with your antenna. Switch to
> an alternate antenna or dummy load if possible (tune the KAT500 into the
> dummy load) as a test.
>
> 73,
> Don W3FPR
>
>
> On 11/13/2017 4:41 PM, Kevin der Kinderen wrote:
>
>> Waiting on an answer from Elecraft but thought I'd also check with the
>> group here.
>>
>> I have a Flex 6500 with KAT500/KPA500 combo. It's been working great until
>> very recently. Within the past couple of days I was intermittently reading
>> high SWR when the amp is in operate. In standby or off everything looks
>> good. As of last night it's not so intermittent.
>>
>> In receive when I switch from standby to operate I'm only receiving the
>> strongest of signals. Everything else disappears almost like the antenna
>> was disconnected.
>>
>> When switching between standby and operate I hear a relay clicking. I'm
>> not
>> sure but it doesn't seem to be as loud a click as I normally hear but I
>> can't be sure.
>>
>> With the amp powered down and the Flex set to 100 watts out everything
>> seems to be working fine. I'm afraid my amp is going to take a trip. Any
>> ideas for things to check?
>>
>> 73,
>> Kev K4VD
>> ______________________________________________________________
>> 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]
>

k4vd

Re: KPA500 Problem

Hmm... alright then. Jim sent me an email with the same conclusion. I need
to recheck all my cabling.

I'm a bit surprised that's the conclusion as simply bypassing or turning
off the amp but leaving it connected made the problem go away. I have some
good cable on there now but can replace each one of them to try it out.
I'll report back later on. I really hope it is just this.

Kev

On Mon, Nov 13, 2017 at 5:19 PM, Michael Walker <[hidden email]>
wrote:

> Hi Kev
>
> Don is 100% right.
>
> I would change all the cables and then test with the amp alone and the
> tuner alone to narrow it down.
>
> I spent 3 days debugging an Acom A1000 issue only to finally out I had a
> bad jumper cable.
>
> Mike va3mw
>
>
> On Mon, Nov 13, 2017 at 5:05 PM, Don Wilhelm <[hidden email]>
> wrote:
>
>> Kev,
>>
>> That behavior can be caused by a coax jumper, either loose or faulty in
>> some way. Make sure the PL-259s are tight and if you can substitute the
>> jumpers with known good ones - particularly the one between the KPA500 and
>> the KAT500 and the one between your transceiver and the KPA500.
>> There are as many problems caused by cables as are caused by equipment.
>> Some cable problems have no apparent problem at lower power, but rear
>> their ugly head at higher power.
>> You could also have a higher power problem with your antenna. Switch to
>> an alternate antenna or dummy load if possible (tune the KAT500 into the
>> dummy load) as a test.
>>
>> 73,
>> Don W3FPR
>>
>>
>> On 11/13/2017 4:41 PM, Kevin der Kinderen wrote:
>>
>>> Waiting on an answer from Elecraft but thought I'd also check with the
>>> group here.
>>>
>>> I have a Flex 6500 with KAT500/KPA500 combo. It's been working great
>>> until
>>> very recently. Within the past couple of days I was intermittently
>>> reading
>>> high SWR when the amp is in operate. In standby or off everything looks
>>> good. As of last night it's not so intermittent.
>>>
>>> In receive when I switch from standby to operate I'm only receiving the
>>> strongest of signals. Everything else disappears almost like the antenna
>>> was disconnected.
>>>
>>> When switching between standby and operate I hear a relay clicking. I'm
>>> not
>>> sure but it doesn't seem to be as loud a click as I normally hear but I
>>> can't be sure.
>>>
>>> With the amp powered down and the Flex set to 100 watts out everything
>>> seems to be working fine. I'm afraid my amp is going to take a trip. Any
>>> ideas for things to check?
>>>
>>> 73,
>>> Kev K4VD
>>> ______________________________________________________________
>>> 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]
>>
>
>

Brian D

Re: KPA500 Problem

Kevin der Kinderen <[hidden email]> wrote:

> I'm a bit surprised that's the conclusion as simply bypassing or turning
> off the amp but leaving it connected made the problem go away. I have some
> good cable on there now but can replace each one of them to try it out.
> I'll report back later on. I really hope it is just this.
>
I had a similar problem recemntly due to a SC diode in the TR switch, all OK
on bypass but not on operate. After changing diode (and checking associated
bits I has problems with power/dissipation on 10 and 6m cured by using a
diode from a different batch.

However, after re-assembly I had intermittent lack of RX, traced to a relay
card used externally for buffering a relay. At the time this board was
unpowered but still in circuit and was holding the KPA500 on TX. A simple
bypass proved it was the culprit and putting its 12v power back on fixed it
for good.

--
Brian D
G3VGZ Yarm England
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Bob McGraw - K4TAX

Re: KPA500 Problem

In reply to this post by k4vd

On PL-259 connectors, make sure they are more than finger tight. I use a
pair of 4" Channel Lock pliers to snug mine after they are finger
tight. Today's PL-259's may look good but indeed with many of them
today, the plating is crap!. Same for coax cable and the way it gets
terminated inside the PL-259. The cable frequently works loose and
causes intermittent connections which may not show up at 100 watts or less.

In my practice, if I find a bad cable, I immediately chop the suspect
PL-259 off of one end. That way the cable can not be accidentally used
until it is properly repaired and checked with a dummy load and my
impedance bridge or antenna bridge.

73

Bob, K4TAX

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k4vd

Re: KPA500 Problem

I've done some testing. I have a good selection of Times LMR-400-ULTRAFLEX
jumpers that I stocked up on from MPD Digital. Never had a problem with any
of their cables and so far it's looking like they are all good.

I set things up as Radio <--> KPA500 <--> DL1500 with new cables in between
and the KAT500 removed from the chain.

Running the radio to 10 watts the radio showed 1.25:1 SWR while the amp was
in standby. When in operate, the SWR on the radio maxed out.

I fired up KPA500 Remote and bumped the radio up to 20 watts. In standby,
radio showing 1.25:1 SWR KPA500 remote reported

Power: 18 w (that's typical)
SWR: 1.1:1
Current: PTT OFF (typical in standby)
Voltage: 74.8
Temp: 22 C

Switched the amp to operated, radio still at 20. KPA500 remote reported

Power: 0 W
SWR: NO RF
Current: PTT OFF
Voltage: 74.8
Temp: 22 C

It's like standby/operate is switching between straight-through and open.
It seems to be falling into place with Brian's description of his recent
problem. I heard no cracks, booms, or sizzles. Smelled no smoke or ozone.
It just started giving me problems intermittently and seems to have finally
settled down into a broke state.

Working with Elecraft to troubleshoot and will share any findings that
might be helpful or garner sympathy. ;)

73,
Kev K4VD
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