I have a Marantz SR9300. I sold it to a guy and gave him a week to check it out. He brought it back because he says the transformer hums and it screws up his CRT TV with the magnetic field. I did not notice this hum whe I sold it to him. But it is there now, with nothing plugged in. I found it funny he bought the unit without even wanting to power it up. I am wondering if he did an old "switcheroo" on my transformer?
Even if he did, I cannot prove anything. What are my best option to fix this?
Are you sure you got the same unit back? Did you check the serial numbers? Now changing a power transformer is a major repair requiring significant skill. If he did change it, he will have left evidence, if you look at the wiring harness from the transformer and the soldered connections, you will see that they have been disturbed.
It is not uncommon for mains transformers to get a little noisy. The AC field problem is not related to the noise, and will be generic to all those units.
Now the transformer will have to be replaced with an identical one from Marantz, if you want the transformer hum to go away. The mains transformer is probably the most expensive component in the receiver, and will be a significant operation to change it, and require high technical skill to do it safely and neatly.
Unless the hum is very loud, I would sell it as is.
