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Author Topic: Jupiter PA Alignment?  (Read 1238 times)

Posts: 77


« on: January 13, 2018, 08:40:16 AM »

Folks, I have a Jupiter that is apparently mis-aligned.
On CW, with the readout at 55%, I get 100 watts out but if I raise it higher then 55%, the power goes to about 140 watts and then my power supply limits it but I believe the radio can do 175-200 watts.
I get 100 watts out with 16 amps.  At that point the internal power meter reads 28 watts
If I lower it from 55% to 32A%, I measure 50 watts out, and the internal meter reads 19 watts
If I switch the internal meter to SWR, it reads 15.9:1 SWR all the time.

There was a modification I heard of (can't seem to find) that said you can do 150-200 watts out with the Jupiter, assume that is what was done.  Does anyone have this mod?
If I cannot find it then I figure I will probably adjust R-258 (PA current limit) to get the 100 watts out....  Then tackle the SWR circuit.  It is odd the internal meter only reads 28 watts when I measure 100 watts out..  Anyone ever seen his before?

Posts: 77


« Reply #1 on: January 13, 2018, 01:25:21 PM »

Well not finding "anything" on this info for a Service Alignment, I looked again at the schematic.
Because I had more then 110 watts out and well upwards of 160 watts, I elected to turn down R-258 as my current was well in access of 20A.  As I turned it down, of course the power went down.  I keep raising the power control on the radio / turning down R-258 until I achieve 100%.  At that point the power was measured at 110 watts.  When I varied the power control it paralleled the external power meter.  Then I adjusted R-83 for 110 watts when power was turned up to maximum and finally turned R-86 for 1:1 into a 50-ohm load what I was using all along.
Now the power set when at maximum is 110 Watts and the radio says 110 watts.  As I turned it down to say 50% I am putting out about 50 watts. 
I checked and had to touch up R-258 and R-83 just slightly but now it is working on all bands, all modes and power on the radio is close to measured.

So as I suspected someone along the past had tweaked the Jupiter for 160 watts and diddled the other pots till it was just non-operational.
I now have a fully functional Jupiter.

Done, de KG9H
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