[Elecraft] Power supply voltage sag during transmit

[Don Wilhelm]

Jimmy,

I did not make any reference to any switching supply.  I have the same 
supply, sans meters.
The meter on the power supply is reading internal to the supply. Check 
on the outside with your DMM.

The terminals on that supply are bolts with the heads on the inside.  
Those bolt heads apply pressure to the solder lugs on the inside.  If 
the nuts on the outside (the ones closest to the enclosure) are not 
tight, there will be considerable voltage drop during transmit.  The 
connections made on the outside must also be tight to assure a low 
resistance.

It is a simple matter to connect your DMM and monitor the voltage as you 
transmit.

73,
Don W3FPR

On 1/29/2017 9:57 AM, James Walker wrote:
> I tried the direct wiring fix first. It didn’t change anything. And 
> the voltage drop was radical. It would go down sometimes from 13 to 11 
> volts. The voltage drop was not indicated on the power supply volt 
> meter. And remember, the big Astron power supply works fine with my 
> IC-7300 and IC-746 off the Rig Runner strip. Maybe those rigs work 
> better with the voltage variation. But something is going on here with 
> either the power supple or the K3. I paid about $200 for the big power 
> supply back in the 90’s. I think the little Astron supply (switching 
> type) was less than $100. Maybe the difference is between transformers 
> and switching technology. Anyway, my nightmare is over with a happy 
> ending.
>
> Jimmy
>
>> On Jan 28, 2017, at 10:27 PM, Don Wilhelm <donwilh at embarqmail.com 
>> <mailto:donwilh at embarqmail.com>> wrote:
>>
>> Compare the voltage directly at your power supply terminals between 
>> receive and transmit.  If it stays up, then check your power cable to 
>> the K3 for adequate size wire and good connections.  If you have a DC 
>> power distribution device like the RigRunner, remove the K3 from it 
>> and connect direct from the power supply to the K3.
>