Hello,
The original point of the thread was can a power supply be upgraded to allow for a higher output current.
The answer is yes but there is some serious changes that have to be made.
First, the output power transistors all have to be doubled if the current is doubled.
Second the input transformer current rating has to be doubled, the input diode bridge current rating hs to be doubled.
Third, the filtering capacitance has to be doubled.
Fourth, any current limit detection circuit has to be modified to allow the higher output current.
Fifth, the heatsinks have to be doubled or enlarged.
Last, it has to be tested at full load.
If it's an old design it should be upgraded with a reference diode rather than a zener which the old supplies used to use. The reference diode is much more stable over temperature.
As a side note, you can build 5 amp power supplies with the higher current version of an LM317 and they are pretty simple with much less parts. That will get you there pretty quick if you just want t linear. IF you want a switcher it takes a little more work.