Chassis grounding a Accuphase e-202

[Chrisr3521]

Hi, just about finished restoring an Accuphase e-202 amplifier and have turned my attention to chassis grounding it, easy enough i hear some people say, well no, not really.

If its switched to intergrated everything is fine and ok, seperate it and put an input to the poweramp in and ground hum damn!

I know that accuphase used to offer chassis ground as part of their upgrades for this amplifier do'es anyone know how to accomplish this without the hum?

Thanks

Chris

 

[Chrisr3521]

Schematic.

 

[AndrewT]

There is no choice when considering Chassis ground.

The Safety Earth MUST be directly connected to the Protective (PE) wire of the mains power system.

You MUST bolt or weld the Green/yellow wire to the Chassis, not optional. Absolutely your responsibility.

 

[Chrisr3521]

Yes i know this and has been done, however as grounding is my achellies heal i was just wondering if getting rid of the ground loop was acheavible with something like a ground lift circuit (bridge, cap, resistor)? And where would i take the ground from?

 

[AndrewT]

Can we assume from your restated question that you are not referring to the Safety Earth?
Are you are referring to the Main Audio Ground? Or the Signal Ground, or the Power Ground, or the PSU zero volts, or some other part?

 

[Chrisr3521]

Sorry, not been clear enough the amp didn't have a saftey ground nor was it double insulated, i have added a chassis (safety ground) and now it has a groud loop.

 

[AndrewT]

There must be one connection from Main Audio Ground (MAG) to Chassis.
If you have ONLY one connection you cannot have a ground loop.

Disconnect from the mains.
Disconnect the MAG to Chassis connection.
Measure the resistance from MAG to Chassis.
If this reads more than 2r2 then your loop problem is somewhere else and nothing to do with the MAG to Chassis connection.

Reconnect the MAG to Chassis.
Power up the equipment and search elsewhere.

 

[Chrisr3521]

Are you are referring to the Main Audio Ground? Or the Signal Ground, or the Power Ground, or the PSU zero volts, or some other part?

Psu 0v.

 

[AndrewT]

Yes the MAG to Chassis connection can be made via the PSU zero volts.
There must be ONE wire from MAG to PSU zero volts. There must be ONE wire from PSU zero volts to Chassis.
And since you now have the Safety Earth connected you must have ONE green/yellow wire bolted to the Chassis.
Equals no ground loop.