For my little home lab, I picked up from eBay a used Kepco ABC series 10V/10A programmable power supply. It had been behaving itself very well up to now, with its output voltage display matching well with my Fluke 77-IV meter with low-power circuits.
I recently picked up a pair of 2 ohm, 100W resistors, and I've been experimenting with the power supply under some real load. Now, if I have the two resistors connected in series to the PSU's outputs, and I ask it to supply 5V, it reads 5.000V and 1.128A, but my meter while reading the PSU's outputs is only showing 4.706V. The ABC series is specified for 0.01% load effect on voltage, so this is way out of spec.
I have the power supply's sense inputs strapped to its outputs.
The manual describes how to calibrate voltage and current: first the open-circuit voltage is calibrated, and then the current through a 0.1 ohm 0.04% 50W resistor is calibrated. My unit's voltage readout is fine open-circuit, so I'm not sure this procedure would address the problem I'm having. I also don't know where to get such a fancy resistor for the current calibration.
Is my power supply bad?
Thanks,
John