Initial power-up check

1. Set your multimeter to DC Volts mode. If your meter is not autoranging, select the 100V or 200V range.
2. Connect the AC power cord and turn on the power.
3. The indicator LED should glow. If not, power off and check the LED's polarity. Also, check the fuse to make sure it has not blown. If you have a blown fuse, do not apply power again until you've identified and corrected the fault.
4. Nothing should get warm at this time.
5. Touch the meter's negative (black) probe on one of the "V-" pads on the output terminal blocks, and touch the positive (red) probe on one of the "V+" pads. The voltage reading should be very close to the desired output voltage (i.e., if your σ11 was built for 24V output, you should read approximately 24V).
6. If you have a reasonably good digital multimeter (DMM), repeat the above step, except with the meter in AC mV mode. Depending on the sensitivity of your DMM, you should read no more than 35µV or so. Only the most sensitive meters will register a reading, most would simply read 0mV. This is the unloaded output noise of the PSU. Many DMMs won't produce an accurate AC mV reading when it's riding on a large DC offset, so don't worry about this measurement if your result isn't as expected.
7. If you passed the above steps, then the σ11 should be working correctly.
8. (Optional) If you have a 50&Omega 50W power resistors, you can run a load test of the PSU. Turn off the power and wait 30 seconds to let all capacitors drain. Then, connect the resistor across the V+ and V- pads. Re-apply power. The resistor will get quite hot and the MOSFETs should warm up. Repeat the DC voltage measurements above and the readings should remain stable at the specified voltages. Run this test for as long as you like.
9. Turn off the power, wait 30 seconds and let all capacitors drain.
10. If all is well, you can now connect the load (i.e., the amplifier or other device that the σ11 would supply power to). Use color-coded hookup wire (heavy gauge recommended for longer wire runs), and twist each V+/V- wires together to improve the common-mode noise rejection.
11. Re-inspect all wiring and check for short circuits.
12. Apply power and follow the procedure to setup/adjust/test the amplifier/device.

Warning

• Due to σ11's lack of current limiting protection and very high output current capability, short circuiting its outputs could result in damage even if there is a fuse on the AC mains.
  
  Do not connect the σ11 to the amplifier when the power is already on. This is especially important if the amplifier or device being powered by the σ11 has significant rail capacitance (e.g., larger than 470µF). The current surge required to charge the capacitors is similar to a momentary short circuit condition.
  
  For this reason the σ11's power switch should only be on the AC mains before the transformer, not at its regulated outputs. If the σ11 is located in a separate case than the device being powered and the umbilical power cable becomes disconnected, turn off σ11's power and wait for all capacitors to discharge completely before reconnecting the cable.
  
  
• If you are going to be moving the board, desolder parts or otherwise work on the board after turning off the power, be sure to wait enough time to let all capacitors discharge completely. Stored charge in the capacitors could damage parts if board traces are short-circuited to each other by contacting other objects or the soldering iron.

Troubleshooting

• σ11 operating points (36V output)
• σ11 operating points (30V output)
• σ11 operating points (27V output)
• σ11 operating points (24V output)
• σ11 operating points (15V output)
• σ11 operating points (12V output)
• σ11 operating points (9V output)
• σ11 operating points (5V output)