Testing and Calibration
Note all testing must be done with the heatsink or panel attached to the power devices.
After wiring the unit according to the instructions given in the Users Manual you should apply
power to the unit. Check that no device is running hot. Any sign of smoke or strange smells
turn off the power immediately and recheck the all the external wiring first, and then the
components on the board. Both the +VE and -VE LEDs should be lit and neither should be
too bright or too dim.
With a multimeter, check the DC voltage across the +15V and -15V output terminals. You
should get around 30V or so. Adjust the trimmer so that you get exactly 30.00V. Now
measure the voltage across the +15V and one of the 0V terminals. This should read 15.0V or
very close to it. Check that the voltage across -15V and 0V is -15.0V. It is advisable that the
+VE and -VE LEDs are fitted for this adjustment, or that at least one Oakley or MOTM
module is connected up to the power supply board. This is to ensure that there is some current
running through the series pass devices (Q1 & Q2) which allows them to work properly.
If all is well, then it is time to check the current limit. Put your multimeter into current mode.
Use the 2A or 10A setting. Now put your probes across the +15V and 0V terminals. The
meter should read approximately 630mA (for current limit resistors of 1R) or approximately
780mA (for current limit resistors of 0R82). The orange and green LEDs should both go out
when the probes are in place. There is a problem if either of the LEDs do not come on again
when the probes are removed.
Now do the same for the -15V and 0V terminals. This time we should get a slightly higher
reading of around 730mA. (for 1R resistors) or around 870mA (for 0R82 resistors). This time
only the green LED should go out when the probes are in place.
The current readings you have just taken may be slightly different from what is given here. It
will depend on the ambient temperature, the accuracy of the power resistors and the accuracy
of your ammeter. Expect the actual value to be different by about +/-10%. If it is significantly
different, like 1000mA instead of the expected 630mA, then check your build. While doing the
current limit check you may notice the power devices getting warm. This is perfectly normal.
If all is well, everything is probably working and you can now connect your new supply up to
your modules.
The output voltages will vary a little with load. That is, it will change marginally depending on
how many modules you connect up to the power supply board. Feel free to re-adjust the
trimmer when you add more modules to your system.
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