Never really written a review before but I will try. I have time off work for the next few weeks so I may give it a go Is there an Amperage limit to the PSU that can be used?
No problem, just give your honest opinion, compare with you had before and how it perform. It will help other users in same situation as you to choose something.
Max Amperage not a problem, you can have a 20A PSU, the iron will only draw what it needs and not more. I always recommend a PSU with 1A or 2A more than the device require, because most of the time specs are not real and also is bad to keep the PSU at limit all the time, it will die faster and will be hot, the more amps better colling need to have inside.
In case your PSU don't meet the requirements is what woody said
EDIT: On amazon article they say PSU is 19V, but don't see any amp reference, so you need to check on label when you got it, better if you real check by measuring it. But for sure they include a PSU capable to deliver max power at 19V.
At 19V iron can draw 40W, that means 40W/19V= +/- 2,11A. So the PSU should have 2.5A or more to be safe to get max wattage, but 2A will do the work as well