volume potentiometer Marantz 510

Hi everyone .
I have a marantz 510 amplifier that I use to make measurements with REW but it happens that about halfway through its stroke, the potentiometer that adjusts the volume stops doing its job.
so I can't turn up the volume to make an optimal measurement.
I don't know whether to change it with an original one or whether to replace it with a different and more performing potentiometer.
if it were better to replace it with a potentiometer of other brands, can you tell me which one?.
what do you recommend? . Thank you .
Don't forget that Japanese amplifiers of that era used potentiometers with a fourth leg... for variable loudness, which will diminish the loudness effect at 12 oçlock wiper setting. If you open one you'll understand what I'm saying.

I do not know if that amp has loudness or not...