GE MASTR II PA Final Amplifier Consideration
 By Ray J. Vaughan, KD4BBM

This question was posed on the Repeater-Builder email list.

Problem:   I just returned from our repeater site with a dead MASTR II converted 66 split, 30 watt  mobile that we use as our main club VHF repeater.  From first glance, it appears that we have lost the final transistors in the PA again.

The exciter is putting out its 250 mW and that's all I get at the coax connector.

Modification:   Verify that the finals are open for sure.   This same symptom can be caused by an open jumper between the PA printed circuit board and the harmonic filter.   The sign will be normal current draw, but no output.   If this condition happens for too long, the PA transistors will fail.   This jumper is best replaced by a bit of solder wick, with the middle still flexible.   Hopefully you have this easy to fix problem and you caught it in time.  This modification is referred to as some as the "Inchworm" mod.  A drop of oil willprevent the solder from wicking into the area to remain flexable.

Here is an article that will aid you in fixing the PA.

Ray J. Vaughan, KD4BBM

Information by Ray J. Vaughan, KD4BBM, July 27, 2001
HTML Copyright©  7/28/2001,  Kevin Custer W3KKC