[Elecraft] KPA500 Issue

[Mike K2MK]

Hi Barry,

While your experience suggests that a transistor switch will probably save
the day I also wonder if the problem is the result of the absence or
presence of a pull-up resistor or perhaps a floating common connection
between the rig and amp. Maybe a resistor in the plug would help. I suppose
there is some way to check this out.

73,
Mike K2MK


Barry Simpson wrote
> .............partial quote from Barry..............
> 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.
> 
> 73
> Barry  VK2BJ





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