hifi engine

Pioneer SA520 Amplifier

Hi

I recently hooked up my dads SA520 pioneer amplifier which works great, but one issue, on either the A or B speaker selection, only one speaker plays at a time. I have checked each speaker cable connections on both A&B and all work independently, which tells me external speakers and cables are all working.

Could this be a fuse or just dust??

The system has not been used for many years, so dust build up could be an issue.

If a fuse is gone which i feel is unlikely can anyone recommend what type of fuses these amps used and are they still available.

Many thanks for you help
still can't believe a system of 30 years or so can be hooked up to a dvd player. loving it.