[Swan] Cubic 150A

[dslosty@pipeline.com]

>I would like to adjust the power output on the Cubic 150A.  It is currently
>150 watts!  Can someone with a manual let me know the location of the pot
>that controls the power output?
>
>Thanks in advance!
>
>73 Randy

Randy,

Be careful!
You will soon blow a driver or final xsistor operating the unit at that power!
I'd suggest getting a copy of the tech manual.
It's extremely large and detailed.
W7FG.com can supply a copy.

To do it properly, it's not simply a matter of adjusting one pot.
The following is from the manual:
Quote

Put the unit on 14.200, cw mode. Connect the microphone, a wattmeter and a 
50 ohm dummy load.
Connect an oscilloscope  with a 10:1 probe to the high leg of the reflected 
ALC trimpot (R102) on the preselector board. During the following tests 
limit key down times to 30 seconds or less with intervening cooling time.

Key the unit and adjust mike gain control for an output of 50 watts. Adjust 
the ALC Null timmer (C103) on the SWR/Wattmeter board for minimum DC 
voltage on the 'scope. Disconnect the 'scope.

Turn the mike gain fully clockwise, key the unit and quickly adjust the 
FORWARD ALC trimpot (R103) for 100 to 110 watts.

Remove the dummy load and replace it with a 100 watt light bulb (standard 
house  120v 100 watt bulb). Key the unit and quickly adjust the REFLECTED 
ALC trimpot (R102) for 50 to 60 watts output.

Check the output on all bands for 40 to 70 watts when using the light bulb.
Replace the light bulb with the dummy load. Check all bands for 100 to 110 
watts output, maximum.

Disconnect the coax lead at the antenna connector (no load). Key the unit 
and check that the total supply current is less than 12 amps on all bands.

Connect the 50 ohm dummy load, set the unit to 14 mhz and key the unit.
Adjust mike gain for 100 watts ouput. Quickly adjust the meter trimpot 
(R104) on the preselector board for a 100 watt indication on the meter.

Unquote.

Thus, as you can see, final output power is dependant on the proper balance 
between both the forward AND the reflected trimpots. If you don't do the 
above procedure correctly, you risk losing SWR protection and thereby 
blowing the finals. If the ASTRO-150A is set up correctly, it can operate 
into ANY antenna impedance without damage. Power will just fold back as SWR 
increases. I've replaced several pairs of driver transistors on these rigs 
due to the fact that the previous owners "diddled" with those trimpots 
without doing the proper procedure.

Good luck,

Doug/WA1TUT