[Elecraft] KPA500 Issue

[Barry Simpson]

Good morning to those who responded to me on the Elecraft reflector. Here
is the interim outcome.

I did not mention that the problem arose after connecting my brand new
(yesterday) TS590SG to the KPA500.  The TS590SG has different linear
switching facilities from the TS590S in that there is now provision for
solid state switching to avoid a clicking relay. I was using the solid
state switching set up. I use the same set up with my TS990S and that works
perfectly with the KPA500.

I checked and resoldered the connecting cable and then I interchanged the
cable I use with the TS990S as the Din pin connections are identitical with
the TS590SG. The outcome was exactly the same with the loss of received
signals when the KPA500 is switched to Oper and the little asterisk appears
on the left side of the display. However, the set up still keys the KPA500
perfectly.

I then changed over to the TS990S and with that rig, the KPA500 works
perfectly with the solid state switching.

The conclusion is therefore that from an initial OK position in Stby and
Oper as soon as the first character is keyed, the solid state switch in the
TS590SG "hangs" resulting in the KPA500 being permanently in the transmit
state. The situation only clears when rig and amp are turned off, the Din
plug is removed from the TS590SG and reinserted and both are turned back
on. I can then switch the amp back to Oper and all is fine until the very
first morse character when it all happens again.  So as it stands, there
appears to be incompatibility between the TS590SG solid state amp switch
and KPA500.

As an interim measure, I have rewired the Din plug to use the noisy relay
for the amp control and that works fine. The TS590SG does output 12V to the
solid state switching pin in certain configurations as did the TS590S. I
had a TS590S and I wired a single transistor solid state switch inside the
Din plug and that worked perfectly so I am going to do the same again,
which should solve the issue. Unfortunately, I gave away the TS590S cable I
had made up to the guy I sold the TS590S to. I never got the very bad spike
issue fixed but the buyer did not mind as he doesn't use a linear.

It really is a pity as I thought that the new linear switching circuitry in
the TS590SG was a real step forward but it is not to be, at least not with
the KPA500.

For information and to avoid others having a similar head scratching issue,
I am copying this to the TS590 list as well. As a final point, I can
confirm that the TS590SG has no power spike issue whatsoever and the
average audio level in SSB seems much improved from the TS590S.

Once I have wired and implemented the transistor switch, I will report back
with the result.

73

Barry  VK2BJ

On 31 January 2015 at 00:34, Mike K2MK <k2mk at comcast.net> wrote:

> Hi Barry,
>
> There is an asterisk that appears on the left side of the KPA500 display
> whenever the key out signal from your transmitter is present. You should
> not
> see the asterisk when you are receiving. If you are then is it possible
> that
> you are using the key out signal to operate some other device in addition
> to
> the KPA500?
>
> 73,
> Mike K2MK
>
>
> Barry Simpson wrote
> > My KPA500 has just developed an issue. Specifically when I switch it from
> > Stby to Oper, the level of received signals drops by around 5 or 6 s
> > points. It still transmits fine and there are no adverse SWR indications
> > or
> > loose co-ax plugs. It does the same on all bands. I switch back to Stby
> > and
> > the received signals return to normal.
> >
> > I seem to recall that someone else posted details of a similar such
> > problem
> > some time ago. Any suggestions would be helpful before I email the
> > Elecraft
> > hot line.
> >
> > Barry Simpson   VK2BJ
>
>
>
>
>
> --
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