KPA500 fan shut down problem

[T Gahagan-2]

I’m wondering if anyone else has had this problem?  When I shut down the KPA500 from the front panel the cooling fan turns on and instead of shutting down it continues to run until I turn the power off on the rear panel.  When I turn the  back panel power switch on again the fan immediately comes on and never stops until the back panel switch is turned off.  I originally had this problem 3 years ago and Elecraft had me install a SMT bypass capacitor on the back of the front panel board that I thought had taken care of the problem (It did for several years).  I have reloaded firmware, done a full reset, etc. but the problem persists.  The amp work perfectly other than this glitch.  Any help is appreciated.

Thanks, Todd

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[Jack Brindle-2]

Todd;

You may need to get back to CS about this. When the KPA is powered off from the front panel,it first shuts off the 60V supply, does some other things, then one of the last things done is to turn on the fans. This is an important safety feature to discharge the big power supply capacitors. The fans will run full blast for a short time, slowing to a stop as the capacitors bleed off. Note that even though the 60V source if off, those capacitors will still be charged (and at least some part of the 60V output will remain) until this process completes.

If your fans keep going, it sounds like something is causing the 60V power supply to stay on. Just to make sure, is this what you are saying?
Did you recently open up the KPA, move cables, or anything like this?

Jack Brindle, W6FB
Elecraft Engineering

On Jul 20, 2014, at 7:40 AM, T Gahagan <[hidden email]> wrote:

> I’m wondering if anyone else has had this problem?  When I shut down the KPA500 from the front panel the cooling fan turns on and instead of shutting down it continues to run until I turn the power off on the rear panel.  When I turn the  back panel power switch on again the fan immediately comes on and never stops until the back panel switch is turned off.  I originally had this problem 3 years ago and Elecraft had me install a SMT bypass capacitor on the back of the front panel board that I thought had taken care of the problem (It did for several years).  I have reloaded firmware, done a full reset, etc. but the problem persists.  The amp work perfectly other than this glitch.  Any help is appreciated.
>
> Thanks, Todd
>
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[Carl Clawson-3]

Todd:

Yes, I had that problem. It was solved by replacing a defective power
supply board after I contacted [hidden email].

73, Carl WS7L
K3 #486 and more


On Sun, Jul 20, 2014 at 7:40 AM, T Gahagan <[hidden email]> wrote:

> I’m wondering if anyone else has had this problem?  When I shut down the
> KPA500 from the front panel the cooling fan turns on and instead of
> shutting down it continues to run until I turn the power off on the rear
> panel.
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