Hi Steve
Use a light bulb or build a resistor load Using Ohms law equivalent to 90w or what ever the output power is. That’s how we used to test switch mode power supplies on TV's same way
A couple of car halogen headlight bulbs connected in series would suffice in certain instances
P = V x I or P = I^2 x R or P= V^2 / R.
I = P / V or I = (P / R)2
V = (P x R)2 or V = P/ I
R = V2 /P or R =P / I^2
using above equations to solve for R (Your dummy Load )
You want the load to be just under specified output power otherwise the over current protection will kick in if you exceed maximum load but you can normally tell as you will hear "Click, Click, Click " Of the swps “Switch mode power supply” as it trips due to either over current or over voltage
See this page if stuck
http://www.electronics-tutorials.ws/dccircuits/dcp_2.htmlHope this helps
MD Harrington
www.harrington.force9.co.uk