I have a onkyo HT-R500 receiver and it keeps blowing fuses.

Anyone that replaces a blown fuse without investigating what caused the fuse to blow is only asking for an existing problem to be made worse. A fuse is a safety link that only normally breaks down when something in the circuit reaches failure point.
By just replacing a fuse it's like you are saying to the equipment.........."Now go on and fry yourself some more like you just did !"
And guess what.........99/100 that is what it will do. This means the repair that may have been minor has now been made major......and may even result in fire or injury to the user...thanks to the user's ignorance and laiise affaire. This is really a safety issue as much as anything else, and in my opinion, shops should not be allowed to sell fuses to other than people who are qualified to inspect equipment for causal fuse failure first prior to replacing them. But then.......we have tried to stop selling cans of paint to minors haven't we?
Oh well !.......... back to the drawing board!

Onkyo HT-R500 5.1 home theater receiver. I have had a recent problem with this receiver. The volume does not come out clearly on all speakers, and it does not increase gradually like it should. I have tried different speaker wire and speakers and nothing else seems to be the problem. The receiver turns on an off fine, and you are still able to hear the sound from the source selected, but it just doesn't sound balanced and you don't have the fine control on the volume. Has this problem occured with any one and what is the correction to this problem.

A receiver that recent usually has a detect circuit that keeps the outputs off until speakers are connected . So, if it bows fuses right away , it's really a power supply issue.
Probably the AC rectifier bridge.

Tech service only.