I have ordered a 1kW step-up transformer. I guess 1kW covers it nicely
but like I already said, I would really like to know how much the devices really consume.
Transformers have two ratings, the "continuous load" rating, and the "tool" rating.
For the same transformer the “tool” rating is higher as it is expected that the item of equipment connected (the tool) will only be used intermittently.
However, you say that you have a 1kW transformer. So even if it is a “tool” rated transformer, it is good for at least a 500 Watt continuous load.
Power (in Watts or W) = Voltage (in Volts or V) x Current (in Amps or A)
So for the Atari ST
240V x 0.5A = 120W, however in practice the normal running current (and therefore power) will be a lot lower. I think Atari were very conservative with the figures they give on the outside case. In STFM machines the PSU is rated at 35W. However some later machines (forget which) have PSU’s that are rated at 50W. But these are the maximum ratings. I would expect the normal running power to be around half that, so about 17W to 25W.
The Megafile may take a bit more, (due to it’s drive motors).
I have never measured the power drawn by a SM 124 monitor, but other similar size (or slightly bigger) screen CRT TV’s and monitors are normally 60W or less when running.
So the 1kW transformer that you have got should be fine, you are nowhere near the limit
Can you solder? I am at work at the moment, but I am sure that the Atari ST PSU’s can be wired for 120V as well as 240V operation.
Hope this helps