Power supply 220VAC/DC 0-30V/0- 1A: not working ok anymore

[Pborsen]

Hi Everyone
I build this power supply in the 80's during my education at an Electronic engineering school.
I designed it to be adjusted from 0 to 30vDC and to adjust the amps limit between 0 and 1 A.
Recently when trying to use it, I can not adjust the tension with the potentiometer anymore. When rotating the potentiometer, it moves from 0V to 30V and can't manage to adjust to another voltage.
I have not run into electronics for years now but can still repair, change circuits,...when I know what to change.
I don't have the diagram any more but can sent pictures of the board.
Any idea where the problem can be?
Thanks in advance.

[pebe]

Can't make any suggestions without seeing the circuit, but a photo may be useful.

[pebe]

Pborsen,
If you are trying to upload a photo, please bear with me. There is a fault with the site at the moment that we are trying to get fixed.

pebe, moderator

[PradeepKumar]

Hey kindly post the circuit diagram. Only then it will be helpful to make replies.