It's hard to say with any degree of certainty what is going on. But, I would power everything down and clean all the connections and make sure none of the wiring has come loose and created a grounding problem. Plug everything back in and if it still makes the noise, do not use it any longer. It's probably not worth repairing and time to get a new one. You got your $200 worth if you've had it for 6 years...no?

I agree with Catch22. If your unit has been sitting with practically no cleaning done to it for six years then dust and oxidation can cause connections to become intermittent and thus produce strange noises. Disconnecting and reconnecting all the connections, cleaning wires and male/female connector ends might fix it. If it doesn’t fix the problem then it most likely is an internal problem. Buzzing and popping sounds are either a sign of a cracked solder joint on the printed circuit board or an electrolytic capacitor failing. The cost of fixing the unit will not be worth it’s value unless you have strong sentimental feeling towards it.
This might me a sign to gift yourself with an upgrade.

xsipower

xsipower wrote:

This might me a sign to gift yourself with an upgrade.

xsipower

Spoken like a true audiophile enabler.
I like the way you think!

Bill - on the Hill
Practicing Curmudgeon & Audio Snob
- just an “ON” switch, Please –