[Amps] lk-550 woes

[gdaught6 at stanford.edu]

Hi group,

I've got a friend's Amp supply LK-550 with the optional PAC-5 power supply.  

The amp is back for the umpteenth time with melted plates on the tune capacitor.  In 
previous visits, I've filed, polished, etc. and it runs for a while.  Then it comes back 
with melted capacitor plates.  This time, I've replaced the capacitor which is rated at 
3500V.  The PAC-5 puts out very nearly 4000VDC, and that doesn't drop much at 
full output.  That's stressing that poor little capacitor pretty hard.  Mistune a bit, or 
forget which antenna you're on, and there is a light show in the plate tank.

I'm thinking of reducing the DC voltage, but I don't have a schematic of the PAC-5.  
The big transformer has an unused terminal on the primary, but I don't know what it 
is.  Maybe, it's a primary tap that would allow me to drop the voltage a bit.  I can try 
to measure it, but perhaps someone on the list knows, or has a schematic and/or 
manual for the PAC-5.

Thanks in advance for your responses.

73,

George T Daughters, K6GT
CU in the California QSO Party (CQP)
October 3-4, 2009