Parent Directory	IMG_3683.JPG Underside of a board from the ACMP-73. Notice that the entire bottom of the board is covered with copper, and that about 85% of that is grounding. Notice that the ground plane is grounded at each screw terminal.	IMG_3684.JPG Closer shot of the right section of the modded unit.
IMG_3685.JPG The modded 81. Note the enlarged caps. In order from left to right, the big cans are 2,200uF, 1,000uF, 2,200uF, and 1,000uF. In hindsight, they should all probably be 1,000uF. The 2,200uF parts take too long to charge up and start smoothing.	IMG_3686.JPG The one remaining mod between boards. I didn't want to add grounds on the leftmost board itself. This goes from the 24V ground (labeled 24vdi) to the nearest screw. I removed this mod later because it wasn't really necessary after the other fixes and it was a little ugly.	IMG_3687.JPG The underside of that jumper board.
IMG_3688.JPG You can see the grounds from the two rightmost boards here. The minus side of each o those caps is soldered to a heavy gauge wire, and the opposite end terminates in those terminal spades.	IMG_3689.JPG These boards are noisier, so I added a ground wire from this point to the main ground screw on the PSU. These are wired just like the previous picture; the minus sides of the caps are wired to heavy gauge wires that terminate in these terminal spades.	IMG_3690.JPG Here's a spade attached to the second board from the left. More on the next photo.
IMG_3692.JPG Note that the terminal spade in this case is connected to the minus side of two caps on the second board from the left. I ended up removing this mod because it interfered with my ability to move the power connector down to this board.	IMG_3695.JPG Underside photo of a typical ACMP-81 board for comparison with the ACMP-73 board.	IMG_7520.JPG Completed assembly of one unit after phase 2.
IMG_7523.JPG Close-up of the shifted power supply connector. This cable was originally the leftmost connector at the top of the rightmost board.	IMG_7524.JPG Upgraded transistors are clearly visible in this picture (see http://homerecording.com/bbs/showthread.php?t=275506 for more info), as are my rather hackish shields for the toroidal inductors. The shields consist of one layer of Metglas magnetic shielding film covered by a layer of grounded copper self-stick foil.	IMG_7526.JPG A larger view of the previous shot. Note the unused connector where the power cable used to plug into the rightmost board.
IMG_7527.JPG The modified main amplifier board. Notice that one resistor has been replaced with a wire wound resistor to increase the wattage handling on the part so it won't burn up if you leave the volume knob between a certain two switch positions.	New_PSU.png Proposed alternative power supply for the ACMP-81.