With inexpensive practice amps, it is not uncommon for the circuit boards to be secured only by the pots. Often what happens is the amp falls on it's face while there is a cord plugged into the input jack.
This often causes the board to bend and breaks the pots.
Inspect the input jack to be sure none of the solder joints have cracked.
The best way to check if some pots are good is with DMM measuring ohms.
Also you can look with a magnifier to see if the carbon track is cracked (in the same area where the bad pots are cracked).
This often causes the board to bend and breaks the pots.
Inspect the input jack to be sure none of the solder joints have cracked.
The best way to check if some pots are good is with DMM measuring ohms.
Also you can look with a magnifier to see if the carbon track is cracked (in the same area where the bad pots are cracked).