[Arran]

Sam, here is a picture of what I made for the power supply.  It is from a common issue schematic.  The power transformer has a split primary, two 125 V inputs and you use one for producing the 90V.  As I recall (hard for me) there are two 6V secondary windings, only one used to provide a regulated 1.5V for the filaments.  I hope this helps.
Jerry  PS: sorry for the cruddy picture quality.

[Image: http://i303.photobucket.com/albums/nn129...age006.jpg]

Jerry;
  That's the more formal way of building a battery eliminator, what we used to do was look for an old style isolation transformer from a razor outlet for the B+ side, and a 6.3 volt transformer either a filament type or one from a suitable sized wall wart, and use that as the base. Sometimes if you got lucky you could find a razor transformer with enough of a gap between the windings and the iron to wind a home brew filament winding.
Another trick is to use two 6.3 volt filament transformers, secondary to secondary, and take the B+ voltage off the primary of the second transformer and steal the 6.3 volts from between the two secondaries. If you are good at collecting and parting out junk electronics the possibilities are just about endless for what you could use to build power supplies.
Regards
Arran