It is often much faster and less expensive to repair your audio equipment. However, if you don’t have any background in electronics and I usually do not recommend opening the equipment due to safety concerns. Instead, you should refer any repair to a qualified service facility. Those facilities which are able to repair certain brands are usually listed by the manufacturers. However, you could also go and look at that Yellow Pages and find repair shops. Many repair shops will usually be able to repair most common brands.
If you products that has warranty then obviously the best course of action will be to return the product to the retailer or manufacturer. As long as a product is covered by warranty, the repair or replacement be free of charge. However, sometimes the manufacturer will ask you to pay for shipping at least when shipping the product back to the repair facility. However, shipping usually is a lot less than paying for labor when it comes to repairing equipment. If you do have a device which cost less than $50 then paying for repairs usually not worth it because labor costs rather high in the United States.
Instead it is probably easier to just replace the equipment. That will not only be quicker but also you will have another manufacturer warranty which will cover the device for at least another year. However, if you do have a more expensive product which is not covered by warranty and you don’t want to pay for someone to have it fixed then you can do certain repairs yourself.
Obviously, you might not be able to have the replacement components but at least it will be able to check whether there are any short-circuits or loose connections. The first step in the repair is to open the enclosure. Refer to the drawing that is in the user manual or try to download a repair document which will show you the location of each opening and screw that you will need to remove.
After opening the enclosure, you can do a visual inspection to determine whether there any obvious the facts. If some components have turned black then those have blown need to be replaced. However, if you don’t see any obvious damage then I would try to disconnect and reconnect all of the connectors to see if the problem goes away. Also, make sure the cable which connects power to your equipment is okay. Before you plug in power, however, make sure that you close the enclosure again to prevent the risk of electric shock.