Hello
I'm currently troubleshooting a Rotel RCC-945 cd player. It has what seems to be a ground hum. The noise starts at power up when the relay switch clicks (this relay is located by the output terminals). I re-soldered some solder joints that looked suspicious to the eye. These include the output terminals and power supply capacitors. This is the only unit plugged into the amplifier. When powered off and connected to amplifier, there is no hum. I tried a separate wall outlet and another cd player to make sure it's not the amplifier itself.
I checked if there was a short on the output terminals. When doing so, there was no short but, I noticed the ground terminal of the output jacks not having continuity to the chassis ground. Correction... I just realized when switching my probes around I have continuity. If negative lead is on output terminal and positive on chassis ground there is continuity but, not the other way around.
Looking at the schematic, I noticed all the ground connections use a chassis ground symbol except for the output jacks. These are connected to chassis ground and also have a small capacitor connecting to earth ground. Can anyone explain the difference between earth and chassis ground in this instance?
Just to experiment, I removed the small capacitors from the left and right output terminals and connected a wire from the ground terminal directly to chassis ground (removing the caps from the circuit) and the hum stopped but, I get audible noise from the cd transport (motor noise as the tray moves in and out). This noise only happens when changing cd's not when playing music.
Since I've been focused on the main board, I was considering removing all connections to the other circuit boards and reconnect them one at a time until the noise returns hoping to narrow down the location. Before doing this, I wanted to get everyone's opinion.
I've uploaded screenshots of the schematic. The full schematic is available on HiFi Engine.
Thanks for your time!
I'm currently troubleshooting a Rotel RCC-945 cd player. It has what seems to be a ground hum. The noise starts at power up when the relay switch clicks (this relay is located by the output terminals). I re-soldered some solder joints that looked suspicious to the eye. These include the output terminals and power supply capacitors. This is the only unit plugged into the amplifier. When powered off and connected to amplifier, there is no hum. I tried a separate wall outlet and another cd player to make sure it's not the amplifier itself.
I checked if there was a short on the output terminals. When doing so, there was no short but, I noticed the ground terminal of the output jacks not having continuity to the chassis ground. Correction... I just realized when switching my probes around I have continuity. If negative lead is on output terminal and positive on chassis ground there is continuity but, not the other way around.
Looking at the schematic, I noticed all the ground connections use a chassis ground symbol except for the output jacks. These are connected to chassis ground and also have a small capacitor connecting to earth ground. Can anyone explain the difference between earth and chassis ground in this instance?
Just to experiment, I removed the small capacitors from the left and right output terminals and connected a wire from the ground terminal directly to chassis ground (removing the caps from the circuit) and the hum stopped but, I get audible noise from the cd transport (motor noise as the tray moves in and out). This noise only happens when changing cd's not when playing music.
Since I've been focused on the main board, I was considering removing all connections to the other circuit boards and reconnect them one at a time until the noise returns hoping to narrow down the location. Before doing this, I wanted to get everyone's opinion.
I've uploaded screenshots of the schematic. The full schematic is available on HiFi Engine.
Thanks for your time!
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