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KPA500 RX Attenuation and TX Without Amp Key

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Mark Goldberg

KPA500 RX Attenuation and TX Without Amp Key

I will contact Elecraft tomorrow, but posting in case someone
recognizes the symptoms.

I just put together a new KPA500 kit. When I select Operate, the RX
through the amplifier is significantly attenuated, many 10s of dBs.
The amp will also amplify even with nothing connected to the PA Key
RCA jack. It seems to amplify OK, 35W in gives 400W out. In Standby
the RX and TX pass through the amp as expected.

It seems to me that it thinks PA Key is enabled all of the time, so
when I switch to operate it is in TX mode immediately. I do not see a
short at the RCA jack.

Any idea of what is going on?

Mark
W7MLG
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Ken Wagner K3IU

Re: KPA500 RX Attenuation and TX Without Amp Key

The only thing that comes to mind, Mark,
absent a failed component someplace, is
perhaps one of the ribbon cables is
incorrectly installed. Good luck!
73, Ken K3IU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

On 11/15/2015 3:24 PM, Mark Goldberg wrote:

> I will contact Elecraft tomorrow, but posting in case someone
> recognizes the symptoms.
>
> I just put together a new KPA500 kit. When I select Operate, the RX
> through the amplifier is significantly attenuated, many 10s of dBs.
> The amp will also amplify even with nothing connected to the PA Key
> RCA jack. It seems to amplify OK, 35W in gives 400W out. In Standby
> the RX and TX pass through the amp as expected.
>
> It seems to me that it thinks PA Key is enabled all of the time, so
> when I switch to operate it is in TX mode immediately. I do not see a
> short at the RCA jack.
>
> Any idea of what is going on?
>
> Mark
> W7MLG
> ______________________________________________________________
> 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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Edward A. Dauer

KPA500 RX Attenuation and TX Without Amp Key

In reply to this post by Mark Goldberg

Mark —

There may be some non-anecdotal data about this, but just from my
experience having 35 watts in and 400 out is not typical. On most bands I
run about 23 - 25 in for 500+ out, using a K3 as the driver.

Ted, KN1CBR

>------------------------------
>
>Message: 20
>Date: Sun, 15 Nov 2015 13:24:46 -0700
>From: Mark Goldberg <[hidden email]>
>To: Elecraft Mailing List <[hidden email]>
>Subject: [Elecraft] KPA500 RX Attenuation and TX Without Amp Key
>Message-ID:
> <CAKn+a3uBpE2dTAwSF+oi+EHj5XAyZ_d3fy=[hidden email]>
>Content-Type: text/plain; charset=UTF-8
>
>I will contact Elecraft tomorrow, but posting in case someone
>recognizes the symptoms.
>
>I just put together a new KPA500 kit. When I select Operate, the RX
>through the amplifier is significantly attenuated, many 10s of dBs.
>The amp will also amplify even with nothing connected to the PA Key
>RCA jack. It seems to amplify OK, 35W in gives 400W out. In Standby
>the RX and TX pass through the amp as expected.
>
>It seems to me that it thinks PA Key is enabled all of the time, so
>when I switch to operate it is in TX mode immediately. I do not see a
>short at the RCA jack.
>
>Any idea of what is going on?
>
>Mark
>W7MLG

Jack Brindle-2

Re: KPA500 RX Attenuation and TX Without Amp Key

In reply to this post by Mark Goldberg

Mark;

Recheck the ribbon cable connections in the amplifier. This sounds like a connector
is off, either to a side or more likely one complete row of pins is off. My suspicion
is the 14-pin cable going to the front panel, but it could be the larger cable going
to the IO board. You also might try reseating these cables to make sure they are
connected properly.

- Jack Brindle, W6FB
Elecraft Engineering

> On Nov 15, 2015, at 12:24 PM, Mark Goldberg <[hidden email]> wrote:
>
> I will contact Elecraft tomorrow, but posting in case someone
> recognizes the symptoms.
>
> I just put together a new KPA500 kit. When I select Operate, the RX
> through the amplifier is significantly attenuated, many 10s of dBs.
> The amp will also amplify even with nothing connected to the PA Key
> RCA jack. It seems to amplify OK, 35W in gives 400W out. In Standby
> the RX and TX pass through the amp as expected.
>
> It seems to me that it thinks PA Key is enabled all of the time, so
> when I switch to operate it is in TX mode immediately. I do not see a
> short at the RCA jack.
>
> Any idea of what is going on?
>
> Mark
> W7MLG
> ______________________________________________________________
> 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]

Barry Simpson

Re: KPA500 RX Attenuation and TX Without Amp Key

In reply to this post by Mark Goldberg

Hi Mark

I can relate to what you are experiencing with the KPA500.

You do not mention which rig you are using to drive the KPA500 or how you
have the transmit switching configured.

I bought a new TS590SG some months ago and set it up using the solid state
switching which on the face of it is exactly the same as the TS990 which
works perfectly with the KPA500.

However, with the TS590SG, all it did was exactly as you describe. What is
happening is that the transmit switching arrangement - whatever it is that
you are using - puts the KPA500 permanently in a transmit state and then it
works normally to amplify the signal when you key the rig (or horror of
horrors speak into the microphone.

If by any chance you are using a TS590SG you can test the amplifier for
correct operation by changing to the relay switching rather than solid
state.

In my case, the matter was resolved after some liaison between the
Australian Kenwood Service Centre and Elecraft determined that the pull up
or pull down resistor ( I can't remember which it was) in the TS590SG was
too low such that it put the KPA500 permanently in a transmit state.
Kenwood simply increased the resistor appropriately and now it works fine
just like the TS990.

I hope that might point you in the right direction.

73

Barry VK2BJ

On 16 November 2015 at 07:24, Mark Goldberg <[hidden email]> wrote:

Mark Goldberg

Re: KPA500 RX Attenuation and TX Without Amp Key

I am using the relay contact in the TS-590S, not SG, but the amp us in TX
mode with nothing connected to the PA Key jack, which should not happen.
With nothing but RF in and out connected to the rear panel it goes into TX
mode when I select Operate.

73,

Mark
W7MLG
On Nov 15, 2015 10:29 PM, "Barry Simpson" <[hidden email]> wrote:

> Hi Mark
>
> I can relate to what you are experiencing with the KPA500.
>
> You do not mention which rig you are using to drive the KPA500 or how you
> have the transmit switching configured.
>
> I bought a new TS590SG some months ago and set it up using the solid state
> switching which on the face of it is exactly the same as the TS990 which
> works perfectly with the KPA500.
>
> However, with the TS590SG, all it did was exactly as you describe. What is
> happening is that the transmit switching arrangement - whatever it is that
> you are using - puts the KPA500 permanently in a transmit state and then it
> works normally to amplify the signal when you key the rig (or horror of
> horrors speak into the microphone.
>
> If by any chance you are using a TS590SG you can test the amplifier for
> correct operation by changing to the relay switching rather than solid
> state.
>
> In my case, the matter was resolved after some liaison between the
> Australian Kenwood Service Centre and Elecraft determined that the pull up
> or pull down resistor ( I can't remember which it was) in the TS590SG was
> too low such that it put the KPA500 permanently in a transmit state.
> Kenwood simply increased the resistor appropriately and now it works fine
> just like the TS990.
>
> I hope that might point you in the right direction.
>
> 73
>
> Barry VK2BJ
>
> On 16 November 2015 at 07:24, Mark Goldberg <[hidden email]>
> wrote:
>
>> I will contact Elecraft tomorrow, but posting in case someone
>> recognizes the symptoms.
>>
>> I just put together a new KPA500 kit. When I select Operate, the RX
>> through the amplifier is significantly attenuated, many 10s of dBs.
>> The amp will also amplify even with nothing connected to the PA Key
>> RCA jack. It seems to amplify OK, 35W in gives 400W out. In Standby
>> the RX and TX pass through the amp as expected.
>>
>> It seems to me that it thinks PA Key is enabled all of the time, so
>> when I switch to operate it is in TX mode immediately. I do not see a
>> short at the RCA jack.
>>
>> Any idea of what is going on?
>>
>> Mark
>> W7MLG
>> ______________________________________________________________
>> 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]
>>
>
>