[Elecraft] Help Needed for KPA100 Amplifier

[Dick Dievendorff]

Carter:  this may be a serial communications problem between the KX3 and KXPA100.  Just as a diagnostic step, try turning the amp on with its power slide switch. It should stay on.  

To avoid needing to use that slide switch all the time, there is a serial command sent periodically from the KX3 to the amp telling it to switch on.  That command must be repeatedly received to keep the amp on.  If your serial cable is intermittent (not fully seated?) all the KX3 messages may not be arriving at the amp, and the amp turns itself off after a period of silence from the KX3. Another serial cable might also be helpful.

Good luck!
73 de Dick, K6KR

> On Aug 12, 2021, at 09:45, Carter Craigie <carterwc128 at gmail.com> wrote:
> 
>  My problems all started when I moved my Elecraft KX3, PX3, and the ASTRON
> RS-35A PS from the garage upstairs to the second floor. At first I noticed
> that my Amp would put out only about 70-80 Watts. Then the output went
> lower and lower until the Amp would not turn on. See below.
> 
> Here follows what I know at this stage:
> 
> The AWG 10 power cable from my ASTRON 35A PS to my Elecraft KPA100 amp is
> about four feet long. At the terminals on the PS I measure 13.83 v and I
> measure exactly the same at the cable’s end’s Anderson PowerPoles. (The
> back of the amp accepts only Anderson PowerPoles.) There are two sets of
> these PowerPoles, and the manual for the amp suggests using the lower set
> for the Amp, and that’s what I have done. The manual recommends plugging in
> the KX3 on the upper PowerPoles, and I have done that as well. And the
> radio turns on, no matter whether the Amp is working or not.
> 
> To turn on the Amp I have to go to the Menu on the KX3, and rotate the knob
> above the Menu button until I see “PA OFF.” Then I turn the main VFO knob
> until the OFF changes to “ON.”
> 
> Some Indicator LEDs on the amp turn on:
> 
> ON (indicating the Amp has been turned on)
> ANT 1 (indicating Antenna 1, the one I use to go to the antenna)
> Mode MAN (indicating manual control—which I wish indicated Auto, for
> automatic control)
> FAULT (indicating SYS (I presume this stands for System) for which I could
> find no helpful explanation in the manual).
> 
> After about 10 seconds the Amp turns off!
> 
> I need the Amp to turn on so that I can use the KPA100 Utility Program to
> do any troubleshooting, but that is not possible, since the Amp will not
> remain on for longer than those ten seconds I mentioned above.
> 
> Without the amp I can use my KX3 rig at up to 15W and can use the KP3
> panadapter as well, so all is not lost! The harnessed set of cables
> connecting the Amp, the KX3, and the KP3 all go through the Amp, and they
> show they are doing their job of connecting the KX3 with the KP3. I just
> had a very nice CW QSO with a station in Massachusetts and the reports were
> 599 both ways. Joy!
> 
> All of my cables are fairly well dressed, with no desktop clutter.
> 
> I don’t know what to do next.
> 
> Any suggestions or questions, please?
> 
> 73,
> 
> Carter, N3AO
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