[TMC] My PAL-500

[telegrapher@att.net]

It lives again!!!!!!

Finally got the PAL-500 power supply fixed and now the amp is running again.  
I built a fixture from some "L" shaped fiberglass panel that i had in the 
shed.  Mounted the 3 screen voltage dropping resistors on terminal strips 
bolted to the fiberglass.  The resistors are about 3/8's inch off the panel 
and totally insulated from any arcing possibilities and there shouldn't be 
any heat problems either.  The resistors are mounted at about a 45 degree 
angle from vertical so none of the heat from any resistor will affect any 
other resistor.

Fired it up last night into a dummy load and was able to get about 175 W of 
carrier out of the 4CX-250 finals.  I suspect that they are not the best of 
condition.  

I found that tuning the beast can be a touchy job because the procedures in 
the manual are not the clearest.  Probably a new set of 4CX350's or the 
reliable 250B's will get me the extra 25 watts as if that would make any 
difference on the receiving end.  Ha!

One of the things that is still a little funny is that there is a SSB/CW 
switch on the back of the AMp.  Only reference to it is that you set it to 
SSB when setting the idling current, there after returning it to the CW 
position.  According to the MFGR specs its not rated for AM but neither is 
the -350 amp but tune up procedures i have give AM carrier tuneup 
instructions even though it doesn't have a means of switching between 
SSB/CW.  I suspect that this probably functions in Class "C" for AM.  ANy 
experts in its operation out there?  I'd like to correspond with someon using 
one on the air in AM mode and what their meter readings etc are.

200W carrier is max that it can be run at under the given meter readings and 
voltages.  And actually i don't see any reason to run it at a higher level.  
Unless you can get another 100W, it wouldn't be worth the strain on the tubes 
or power supply in my opinion.  

I'm driving it with a GPE-1A for AM operation.  Now to trim the antenna so i 
can get some RF on 3870/3885.

Its been a struggle but its also been a good learning curve....

Larry
W0OGH