[Elecraft] P3 abnormal shut off problem

[Tom Azlin W7SUA]

Thanks Don.

I measured the power supply sag at the power supply to be about 0.05 
volts. Replaced the cables with larger gauge and still had a problem, 
perhaps internal to the K3. Switched to feeding the P3 directly from the 
power supply ( an Astron 70, but switch to Alinco 50 amp with same 
results) and now the P3 is rock solid. I did order the K3 mod to raise 
the current limit from 0.5 to 1 amp as suggested by Elecraft. And will 
be making that Aux DC out to P3 cable of heaver gauge.

Now thinking on why the K3 voltmeter would show such a large drop.

I do use ring terminal lugs. Will be making higher gauge short as 
possible cables to see if that helps the sag shown on the K3 voltmeter. 
Also plan to set up a second DVM to watch both power supply and input to 
the K3 at the same time.

Still trying to shoot the trouble. Also got suggestions from Elecraft 
tech support and others.

Thanks and 73, tom w7sua



On 10/26/2019 4:03 PM, Don Wilhelm wrote:
> Tom,
> 
> That sounds strange.  I would first suggest checking all the Power 
> Supply to K3, and either K3 AUX DC to P3 or the Power Supply to P3 power 
> cables for loose connections.
> 
> A drop from 14.5 to 14.7 volts down to 12.8 volts indicates a high 
> resistance power cable or a bad power supply.
> 
> Measure the voltage at the power supply terminals to determine whether 
> it is the power supply or the cables - if the voltage stays up at the 
> power supply terminals, but the voltage sags at the K3 end, the cable is 
> to blame.
> 
> OTOH, if the voltage at the power supply terminals sags significantly, 
> then the power supply regulation is at fault.
> 
> Make certain all power cable connections are tight.  Power cables 
> wrapped around the terminals are suspect (use ring terminals), as are 
> the power supply terminals designed to "insert the wire and flip the 
> lever" which may not guarantee a good tight connection.
> 
> 73,
> Don W3FPR
> 
> On 10/25/2019 5:44 PM, Tom Azlin W7SUA wrote:
>> Hi. My P3 has started turning off a few seconds to a minute after I 
>> turn on my K3/P3 or when I then try to turn my P3 back on. I was 
>> watching and saw no error message like low voltage. Watching also the 
>> voltmeter on my K3 and stayed at 14.5 to 14.7 volts. dropped power 
>> supply to 14 volts and it still shut down. Did a tune and voltage was 
>> 12.8 then back to 14 then afterwards it shut off.
>>
>> Is my power supply not holding up properly?
>>
>> Will dig out a spare power supply next.
>>
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