Amp Power Supply

Pi-Amp Power Supply and Chassis
Pi-Amp Power Supply Electrical Schematic

Power Supply Parts Description No. Supplier Stock No. USD ea. Total
T1 TRNS, 300VA, 40V, Center Tap 1 Antek AN-3240 36.00 36.00
BR1 RECTIFIER BRIDGE 200V 25A D-34A 1 DK 26MB20A-ND 8.87 8.87
CP1, CP2 CAP 12000UF 80V ELECT TUP SERIES 2 DK P10032-ND 12.07 24.14
CP3 CAP .1UF 250VDC METAL POLY CAP 1 DK EF2104-ND 0.34 0.34
AC1 AC Receptacle IEC 320-C14 1 DK Q210-ND 0.70 0.70
PC1 Power Cable, NEMA 5-15P to IEC 320-C13 1 DK Q125-ND 4.1 4.10
FH1 HOLDER FUSE 3AG .500"L 1POS 1 DK 3536K-ND 1.55 1.55
FH2 HOLDER FUSE 3AG 2.375"L 4POS 1 DK 3539K-ND 5.28 5.28
F1 FUSE 8A 250V T-LAG GLS MD 4 DK 283-2755-ND 1.00 4.00
F2-F5 FUSE 5A 250V FAST AGC GLASS 8 DK 283-2635-ND 0.70 5.60
R52 RES 3.9K OHM 2W 5% METAL OXIDE 2 DK OY39GK-ND 0.25 0.50
R53 RES CERAMIC COMP 100 OHM 2W 1 DK OY101KE-ND 1.28 1.28
TS Terminal Strip 1 NA Generic 5.00 5.00
S1 SWITCH TOGGLE DPST 5A SLDR 5PCS 1 DK 360-2087-ND 7.65 7.65
Total NA NA NA NA NA 105.01

Tip For Soldering Wire Leads to Small Components
  • Measure and cut the wire leads. Include enough excess to route the lead from that component to the final connection.
  • Strip the component end of the lead back, twist the strands together, apply flux and tin with a generous amount of solder.
  • Secure the small component gently with a bench vice, locking pliers, mount point, masking tape, etc.
  • Apply flux to the component lead and tin with a generous amount of solder.
  • Attach the lead to the component by touching the tinned leads together and then applying the soldering iron tip. As soon a the solder flows between both leads, remove the iron while holding the lead steady until the solder hardens.
  • It is generally not necessary to twist the leads together or insert the lead through a hole in a solder lug because the solder is strong enough. De-soldering components that have been mechanically joined before soldering can be time consuming.
  1. Attach the terminal strip to the chassis about 1" from the ground clip and parallel to the right channel amplifier fin with two #6 counter sink machine screws. The terminal strip simplifies connection between transformer, PSDU and amplifier boards by making these components modular.
  2. Solder the snubbing capacitor to the AC terminals of the rectifier. Wrap and solder the leads as close to the body of the rectifier as possible to avoid interference with the slip on terminals.
  3. Remove the PSDU and attach the fuse buses (F1-F5) to the rectifier post. Install washers between to allow passage of the capacitor wire ties. Attach the bridge rectifier to the top of the rectifier post with a 1/4" machine screw.
  4. Mount the toroid transformer to the toroid bracket. A new transformer will come with two round rubber disks and steel washer for mounting. One disk is placed between the transformer and bracket. The other is placed between the transformer and washer. Since the transformer is mounted on edge, place a small piece of foam or cardboard between it and the chassis base to protect the windings. The primary and secondary leads should face toward the bracket. The center bolt (or all-thread) should be cut so no excess is protruding.
  5. Install the power switch on the controls panel.
  6. Wire the circuit according to the schematic above. The wiring on the primary and secondary side of the transformer should be 14 gauge stranded copper hook up wire. The wiring from the DC side of the rectifier should be 18 gauge stranded copper.
  7. Power up the supply and measure the DC voltage at the terminal strip. It should measure "+" and "-" 56 - 59 Volts.

    Pi-Amp Power Supply
  8. The bleeder resistors (R52) are shown below. One end of each is soldered to the rectifier connectors (+/-). The other ends are joined and grounded to the chassis using the rectifier bolt.

    Pi-Amp Power Supply Distribution Unit Close View