[Elecraft] KPA-500 Failure

[Rick NK7I]

It sounds like blown FETs.  It may be time to ship it to CA where 
any/all upgrades can be done as well as repair.

They're a little backed up, so it may take a few weeks.  Parts and shop 
time too of course.

Call the techs to discuss it and get an RSA and ask if they want you to 
pull the transformer to save shipping weight/cost.  You MUST have the 
RSA (write it on the box, a cover letter inside and with any email 
discussion once it's issued).

The tech indicated that damage to the FETs may be cumulative over time, 
so it may not be THIS event.  But it won't hurt to go through the entire 
antenna and feed system to be sure.

Or you can dive in to repair it; if you feel qualified.

Sorry, been there too.

Rick nk7i

On 4/23/2024 6:52 PM, Dick Bingham wrote:
> Greeting to everyone
>
> I have read the KPA500 operator manual in hopes of solving my
> issue and have found nothing that solves/fixes the problem.
>
> This amplifier has been a workhorse for many years and today
> after the KAT500 antenna tuner searched/found a 'match' for a new
> antenna, I selected OPER on the KPA500, and applied drive power
> to the amplifier.
>
> Immediately, the amplifier displayed a momentary overload indicated
> by the top row of LEDs (power indicator ones) all flashing ON after
> which, the amp FAULTED and shut down. The RF drive level was
> around 20-watts and should have provided about 300-watts output at
> the time this occurred.
>
> I tapped the OPER/STBY button and tried to activate the amplifier and
> found there is no response to incoming RF drive.
>
> I removed/reapplied 'mains' power, pressed the 'EDIT' and ON keys
> simultaneously to reset everything and that did not correct the problem.
>
> The power supply voltage is in spec so no issue there.
>
> With the OPER light GREEN and slowly increasing the RF drive level
> to the amp, there is a point where an internal relay 'click' can be heard,
> the 50-watt LED on the top row of LEDs turns red and the FAULT light
> turns red.
>
> I could not detect any sign of smoke (nose/eyes) so have not opened
> the case to look for burned parts.
>
> Before I open the 'case' and look for obvious problems, any observations
> or suggestions received here will be appreciated. Kinda looks like blown
> amp power FETs.
>
> Dick - w7wkr
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