[Elecraft] KPA500 fan won't shut off

[Bob McGraw K4TAX]

In looking at the schematic, I see the fan is controlled by a MJE182 
{Q5}.  If this transistor shorts the fan runs at full speed.   I didn't 
see a relay in the circuit, but I could have missed it.

73

Bob, K4TAX


On 11/26/2019 3:29 AM, Eric Norris wrote:
> As Jack Brindle noted (and he would know), it appears to be a stuck relay.
> If you don't want to send the amp back to the mothership, I'm sure Elecraft
> Support could identify the relay, and if you can do rework, you could
> remove the bad one and replace it yourself.
>
> 73 Eric WD6DBM
>
> On Tue, Nov 26, 2019, 12:57 AM Grant VK5GR <vk5gr.radio at gmail.com> wrote:
>
>> Eric,
>>
>>
>>
>> I reloaded the firmware tonight – no change (in fact I upgraded it from
>> 1.47 to 1.54).
>>
>>
>>
>> If I plug the mains cable in the fans power up immediately. If I then turn
>> the amplifier on, the amp works normally. When I power it off from software
>> or the front panel the fans spin up and stay running.
>>
>>
>>
>> Is there something I can look at here in VK I wonder? I really don’t want
>> to have to ship it back to Elecraft for this.
>>
>>
>>
>> Regards,
>>
>> Grant VK5GR
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> *From:* Eric Norris [mailto:norrislawfirm2 at gmail.com]
>> *Sent:* Tuesday, 26 November 2019 2:20 PM
>> *To:* VK5GR
>> *Cc:* elecraft at mailman qth. net
>> *Subject:* Re: [Elecraft] KPA500 fan won't shut off
>>
>>
>>
>> Reload the firmware.
>>
>> 73 Eric WD6DBM
>>
>>
>>
>> On Mon, Nov 25, 2019, 6:51 PM VK5GR <vk5gr.radio at gmail.com> wrote:
>>
>> FAN CTL = NOR
>>
>> FANs are idle while the amp is turned on - amp ambient temp was 27C at the
>> time (it was powered up and had been idle for about 20 minutes).
>>
>> I then turned the amplifier off via the front panel push button. I would
>> have expected the FANs to start up for about 10 seconds as they discharge
>> the 60V rail supply but instead the FANs continue to run. the only way to
>> turn them off is to unplug the amp from the mains supply.
>>
>> It is definitely a fault condition and not a menu selection.
>>
>> Thoughts?
>>
>>
>>
>> --
>> Sent from: http://elecraft.365791.n2.nabble.com/
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to norrislawfirm2 at gmail.com
>>
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to rmcgraw at blomand.net