Very loud hummimg and crackling - even when volume turned down
I have just bought a 2nd hand 3020 off Ebay. After it had been on for about an hour it started to emit a loud humming noise. Every time I turn it on it emits the same hum and crackles very loudly. Even when the volume is turn right down. I'm taking it back tomorrow. I'd like to be able to tell him what is wrong with it. Can you help?
Audio Players & Recorders - NAD
Answers & Comments
There are a few variants for this model depending upon the serial number. From your description, there are some capacitors in between the amp stages called coupling caps that are failing. The hum is some DC current being passed through the output stage. The crackling is probably just dirty controls.
Dan