IIRC, there were two different PSUs for the A500s.
Much more.
Initially they came with a "heavy" one that had a big transformator in it. Those had enough power for my heavily expanded A500.
Later they came with a "light" switch-mode power supply, that was not powerful enough for heavily expanded A500s.
It's a better idea to look at what is written on the type plate of the PSUs instead of the weight when doing comparisons.
Type S is light, T is heavy.
http://chain.3dgrafika.cz/joomla/index.php?option=com_geda&Itemid=89As you can see, there are 4.5A units of both types.
