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Thank you To all on this thread! I have done what Mr. Lawrence has shown to do with his pictures. I have the 1.5 version of the 503 board for reference. I am learning as I go and very appreciative of others input. I have completed this modification to a non HD KL-503. Disengaging the driver for this amplifier has made all the difference. Before the disengagement of the driver this unit was very squirrely and unstable as far as output and had drastic changes to the SWR and wattage output from the attenuator knob depending on the dial setting. The heat was obnoxious for the little amount of wattage I was testing the unit at. This amp would get HOT. My 203 at the same output would just be warm to very warm if i was long winded. Reminding that I would only do about 50-60 watts at the pep output of the 203. With the modification for the 503 that puts the driver out of play has tamed this unit tremendously. I didn't want a high drive version because I wanted this unit for low wattage units, but before this modification I took this unit out of service and play. This modification has brought this unit to full service and replacing the 203. Dummy load tested and I have clean clear audio and voice even at max setting dumping 30 plus watts into the input of the amplifier. I have switched to a regulated 40 amp power supply and that has also taken most of the hum out of my signal with this unit on max over the air. Sideband works well also. no complaints. I still notice that after about 40 watts on the output of this amplifier on the average wattage setting this unit will start to back swing just like my 203. This unit will still sound sloppy if it backswings majorly. This amplifier may be better suited for a radio that doesn't have all of the audio doodads like I am running. My Kenwood that i am experimenting with is very wide in audio bandwidth so i am able to hear all the voice imperfections that are in need of cleaning up. Thank you to all who have chimed in on this thread!