power supply question

Yep. A 4A power supply, or even a 400A power supply isn't going to damage the radio. I assume that you intend to get a supply intended to be used to power in-car equipment from the mains.

Yep. If you like loud music, a 4A power supply, or greater, is a must. If you live in a cell in a monastery, then a 1.5A supply will be fine.

In car equipment has to be designed to cope with low supply voltage, so the radio isn't going to be damaged if you overload the supply - but the supply could be.

Unless the power supply that you get is itself protected against overload, it is better to get one with a higher rating than the fuse in the unit. In this case, your unit is fused at 5A, so a 6A supply would be ideal. That way, generally the fuse(cheap) will blow before the power supply (expensive). To be on the safe side, if you use a 4A supply, then change the fuse to a 3A one.

However, if you get a power supply intended to be used to power car equipment from the mains, then the odds are that it will be very well protected against overload, so no worries about changing the fuse.

Gosh that takes me back!

I recall about 30 or more years ago replacing the radio in my car with a better one and rigging the old one up in a box with speaker and power supply for use wherever I was workimg. I remember taking it away on holiday (vacation to you yanks) with us.

I can't remember what the power supply rating was though now. I think the maximum audio output was something around 6W so it probably had something like a 1-2A power supply.