[Elecraft] FW: KPA500 faults

[Mike Fatchett]

St. Lucia is 240v.  I don't know why he would run it on 120v or 110v.

W0MU

On 3/3/2022 1:39 PM, Naumann, Robert, W5OV wrote:
> Bill,
>
> Thanks for the additional information.
>
> Can you tell us if you are running it on 120v?
>
> -Bob W5OV
>
>
> -----Original Message-----
> From: Dr. William J. Schmidt <bill at wjschmidt.com>
> Sent: Thursday, March 3, 2022 10:40
> To: Naumann, Robert, W5OV <w5ov at arrl.org>; elecraft at mailman.qth.net
> Subject: RE: [Elecraft] FW: KPA500 faults
>
> Sorry guys, this is not a trivial line voltage problem.
>
> The 60V line to the PA does not sag that much (starts at 72V goes to 60V under FULL LOAD as measured at the PA)... it's in the voltage divider for the 60V/32 line or the connectors that carry it to the front panel processor for digitizing.  Changes with heat load.  This amp is in the Caribbean and there is plenty of excess heat and corrosion. (nb. I just replaced the current sensing resistor in my K3S for the 100W module due to a hair-line crack... surmise it was heating).
>
>
> Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ
>
> email:  bill at wjschmidt.com
>
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of Naumann, Robert, W5OV
> Sent: Thursday, March 3, 2022 9:11 AM
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] FW: KPA500 faults
>
>
> What line voltage are you running it on?  If you're not on 240v, switching to 240v would be the easiest and most effective improvement.
>
> Doing so yields a 4:1 improvement in line voltage regulation / reduction in voltage drop.  Double the voltage, at half the current draw.
>
> 73,
>
> Bob W5OV
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of Dr. William J. Schmidt
> Sent: Thursday, March 3, 2022 00:39
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] KPA500 faults
>
> I have a KPA500 that faults on low (60 VDC) voltage.  After measuring the power supply voltage at the PA module is perfectly fine.  The voltage read by the processor on the front panel via pin 10 of P1 is lower than it should be and hence the fault condition.  I suspect there is a voltage divider on the LPF board that drops the 60 VDC to something that the processor can read and digitize (in the 0 to 3-5 volt range).  The set of schematics I have do not show the voltage divider anywhere. does anyone have this part of the schematics for the KPA500 so that I can adequately troubleshoot this amp and
> get it on the air for the contest this weekend?   Multiple notes to Elecraft
> have gone unanswered.
>
>   
>
>   
>
> Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ
>
>   
>
>   
>
> email:   <mailto:bill at wjschmidt.com> bill at wjschmidt.com
>
>   
>
>   
>
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