[Elecraft] KPA500 270V ERR

[Paul DeFelice]

I sent the following email to Elecraft support today but would appreciate
any input that the reflector could offer.

 

73 Paul K9NU

 

My KPA500 (S/N 1073) gave me a "270V ERR" message last evening. I removed
the top cover (over-road the interlock switch) unplugged the white connector
from the PA assembly and measured the no-load voltage at the  gray wire.
When AC power is applied, the voltage slowly rises to at best, 180 Vdc
(starts off at about 90 volts and slowly raises to 180 volts in 15 seconds).
The 75 volt supply is work fine. I have removed the power supply board from
the amp. I see no visual damage to the board taking particular notice in the
270 volt area of the PCB. I applied 55 Vac to J1 & J2 via an Isolation
transformer and a variac. One at a time, I paralleled c9 thru c14 with
another 10UF, 100 volt capacitor with no change in the output voltage noted.
The voltage drop across each diode of the 6 diodes (d7, 8, & 9) is around 8
to 10 volts.

Can you give me some input as to where or what to do next? Some test point
voltages would me great.

 

73,

Paul K9NU