HAMPTONe4. WIRING THE POWER ENTRY / PSU INTEGRATION
Or NEXT STEP
1. Cut the 18 gauge gray wire to 4", and strip/tin both ends ½". Solder the ring terminal to one end of the gray wire by pushing the wire into the open end of the terminal so that the exposed wire just sticks out the end of the terminal.
2. Remove the bottom of the chassis from its bag, and install the 4 feet into the 4 holes in the corners using the hardware listed below, all the hardware for this is in the "Chassis hardware" bag. The four flat washers push inside the feet, then the bolt goes through so it is recessed. Put the wire with the terminal you made in the previous step, under the nut of the foot by the large square hole in the back of the chassis, for the power entry module. Just the lock nut is on the inside. Tighten them snug but not over tight (if you do they will likely tear off prematurely). Set the chassis on the bench and make sure it doesn’t wobble. Adjust the feet if it does.
4 x 5/16" 4-40 panhead philips machine screws
4 x #4 flat washers
4 x rubber feet
4 x 4-40 lock nuts
3. Install the power entry module (PEM) to the chassis using the two 3/8" flathead screws in the "Power entry" bag. The ground tab on the PEM (the center one) should be on the top for safety.
4. Install the power switch into the chassis. Put one nut on the switch, then the large washer (bend the tab on it flat), put this through the chassis from the inside. Then put the lock washer on the outside of the chassis, and finally the second nut. Tighten the switch making sure it is aligned straight.
5. Install the fuse holder so the contact at the end (which sticks out perpendicular) is facing down. Though the picture shows the fuse installed, leave the fuse and end cap out for now.
6. Cut/strip/tin the following 18 gauge wire: 2" yellow, 2.5" yellow, 5" blue. Solder the correct lengths of two yellow and one blue piece per the psu schematic. Twist the blue wires around the yellow wires finally soldering it to the switch. Be careful not to overheat the fuse holder. With all of these connections, make certain you fill the holes (especially the power entry module), and that you have no frayed wires that are not soldered in place. Also make sure there is no melted jacket on any of these wires, this is 120VAC!
7. Install the fuse, and end cap by twisting it CW with a small screwdriver.
8. Set your voltmeter to AC volts in a range that will cover the input voltage of your AC power (120 or 220/240). Connect your meter to the two center contacts of the switch. Plug the cord in, and verify you measure 120VAC (or 240VAC) between the two center contacts of the switch when it is flipped up, and goes off when the switch is flipped down. Unplug the cord. Even when the switch is off, if you have the cord plugged in, there is AC power on the power entry/fuse/switch. ALWAYS REMOVE THE CORD AFTER ANY TESTING. NEVER WORK ON THE UNIT WITH THE CORD PLUGGED IN!!!
9. ADD PICTURE: Installing the Mu-Metal transformer shield. Mu metal is a special alloy that dramatically shields AC fields. I found that taking a 0.006" 1" x 10" piece of mu-metal foil, and wrapping it around the power toroid, that the noise floor is reduced by an additional -4dB, from its already low operating point. All kits rev D and higher now include this foil. Remove the self adhesive backing from the mu metal strip. Wrap the strip around the toroid carefully planning the location of the overlap/split and centering the strip height wise. The split in the strip should be at the back of the chassis, away from the audio; with the transformer in front of you and the leads coming out the left, the slit should be on the side farthest from you. DO NOT BEND OR FOLD THE FOIL, it greatly diminishes its shielding. Once the foil has been carefully wrapped around the transformer and secured using the self adhesive, wrap the large tie wrap (your kit may contain 2 that should be connected together) around the transformer in the middle of the mu metal strip, and gently tighten. The foil should not touch the chassis, or any of the power entry contacts on the PEM, fuse, or switch. The effectiveness of the shield is best left "floating", i.e. not grounded to the chassis.
10. Cut/strip/tin the: white, blue, brown, and black wires that are all next to each other on the power transformer to 3" in length. These wires are the AC input. DO NOT CUT THE THICKER BLACK OR RED WIRES THAT ARE IN PAIRS. Twist the thick black pair tightly and leave it full length. Repeat this for the red pair.
11. Install the power transformer using the following hardware:
2" #10-32 Philips panhead machine screw
#10 isolation washer
2 x 2" large rubber washers
2" metal washer
#10 flat washer
#10-32 lock nut.
The isolation washer goes onto the bolt with the flange facing away from the head of the bolt, put this through the bottom of the chassis with the flange going into the hole in the chassis. On the inside of the chassis, place one of the 2" rubber washers onto the bolt, then the transformer, the second rubber washer, the 2" metal washer (concave side down), the #10 flat washer, and finally the # 10-32 lock nut on top. Tighten it with the wires pointing toward the psu board mounting lugs. It is important to orient the transformer this way because it reduces the AC fields in the direction of the audio electronics, it makes a -2dB difference in the noise floor.
12. Wire the power transformer to the switch, and the black and red pairs to the pcb according to the schematic. AC input wiring is different for 120 and 220/240vac (see schematic/p-p drawing).
13. Strip/tin the following wires: 3 x 12" 22 gauge green (ground), 3 x 12" 22 gauge yellow (+50.4VDC), and 2 x 12" 22 gauge blue (+200VDC). Twist them into two sets: channel one will have 2 green, one blue, one yellow. Channel two will have one green, 2 yellow, and one blue. Solder the channel one set to the PCB to the pads show on the schematic, leave the rest out for the moment.
14. Again perform a thorough visual inspection of the bottom of the psu pcb. Make certain all the point-point wires you just attached are clipped off. If they are not they can short to the chassis and damage the psu.
15. Bolt the psu board in place using just 2 of the ¼" philips panhead screws in adjacent corners.