[Elecraft] [Kpa500] voltage tap

[Don Wilhelm]

Eric,

I think if you change the tap on the transformer, the no load voltage 
will be too high.  But you can try it and see if the no-load voltage 
goes too high - move the tap back if it goes too high.

Your problem is likely with the voltage drop on the 120 volt line.  Is 
the receptacle shared with other receptacles in the house?  If so, they 
should all be checked for tightness of the wires to the receptacles.  If 
any use the "back-stab" connections, they should be changed to the screw 
terminals.
If you are not qualified to do those checks, have a licensed electrician 
do it for you.

If you can see your way clear to run a dedicated 120 volt receptacle 
into the area where the amp is located, that will help - have it wired 
with #12 or better #10 wire for the lower voltage drop.

73,
Don W3FPR

On 12/21/2018 5:58 AM, eric norris via Elecraft wrote:
> My KPA500 used to be on a 220v line, but it is now in an area where that is not possible.  It is on 120v, in a 65 year old house.  Further, I am running it on a 10ft appliance type heavy extension cord.  I cannot change these circumstances for the forseeable future.
> No load HV is 78v.  Under full (550w on 40m) load it is 60v.  Current tap is RED.  Should I go GREEN?  Should I leave it on RED?  How much HV boost would that give?  Good/bad/disasterous idea?
> 73 Eric WD6DBM