I took it apart and loaded down the +5 and +12 with a random hard drive I had laying about.
No schematic for a load, but it's pretty easy to work out. Some quick math I did in notepad:
2 or 5W 120 ohm resistor across +12 and GND would sink 100mA (1.2 watts dissipated)
1 or 2W 50 ohm resistor across +5 and GND would sink 100mA (0.5 watts dissipated)
I'd hope (but can't confirm) that would be enough of a load without causing excessive heat, nor needing to be removed if it was used to power an Amstrad PC later on.
Monitor schematics are in with the Amstrad PC manual, http://www.retroisle.com/amstrad/pcs/Or ... ereado.pdf