I have a cheap bench power supply, $50 on ebay, marked RSR HY3002-3. It has two variable outputs and one fixed 5V output. The variable outputs are capable of 2A, the fixed of 3A.
If you put the machine in series mode, it ties the grounds together and locks the slave voltage to the master voltage. Which turns out to be perfect for providing the various power rails needed by a variety of retro computers.
Using the master channel, set the voltage to 12V.
Then, using two paperclips, tie the ground to positive terminal of the slave, and the ground to the negative terminal of the master. Finally tie the ground of the fixed output to the shared ground with a small wire. The result looks like the following:
The negative terminal of the slave provides -12V, the positive terminal of the master provides +12V, the positive terminal of the fixed output provides +5V, all three with respect to the common ground.
Thus, this inexpensive $50 bench power supply provides a 3 voltage setup that's perfect for testing retro computers, no need for multiple power supplies.
