Upgrading a fixed-voltage EuroCom PS-150F to variable-voltage output

[Shark]

Hi guys!

I have a fixed-voltage EuroCom PS-150F power supply (220VAC to 13.8VDC @ 12A constant, 15A max).

For what I saw, the transformer has a single output tap. I measured the voltage after rectifier is around 23V and this is good enough for my purposes.

I would like to upgrade it to a variable-voltage output (1V to 20V) and I'm in doubt between either adapting the existing circuit (fixed 13.8V) or scapping it and making my own from scratch.

Any experiences or advice you could share? Thanks!