Copper strip on Phase Linear 400 inputs?

[LexDM3]

I'm reworking a PL 400 that was converted to balanced XLR inputs sometime in the past. I'll be installing the Watts Abundant protection relay board from AKer Dimlay3 and converting back to unbalanced RCA inputs using the new jacks supplied in the kit.

The installation instructions show that the RCA input jacks are mounted on a copper strip inside the chassis that has ground wires soldered to it. I think there were also insulating fiber washers there originally to insulate the RCA jack grounds from the chassis. The original copper strip and fiber washers are not in mine so I want to put it back in stock form. It looks like they set it up that way to create a single point ground to reduce ground loops and hum.

Could a PL 400 owner check to see if the copper strip is electrically isolated from the chassis? There may be some sort of insulating tape or other material between the copper and the chassis or maybe it's in direct contact.

This picture is from the Watts Abundant relay installation instructions.

Thanks. --Dan

 

[Binkman]

I don't have the unit but both common and positive rca's connectors are isolated from the chassis. Usually the neg. is connected in a switch selector circuit thus isolating the signal path. Some kind of stand offs would work as long as isolated metal wise.

Hey pretty cool looking vintage.

 

[wmgwizard]

The copper plate rests on the insulator holding it just off of the chassis, at least that's the way mine is.

 

[LexDM3]

Thanks Binkman and wmgwizard. That's the information I was looking for so now I know how to put it back together. Many thanks.

 

[mhedges]

Usually the RCA ground connection is isolated from the chassis but is connected to some kind of central grounding hub. Otherwise you have lifted ground which could result in crazy high DC offset issues.

 

[LexDM3]

Thanks, mhedges. There is a ground wire that connects to the copper plate and the RCA grounds. I'll isolate the copper plate from the chassis, connect it to that ground wire, and make sure that it all works well. I appreciate the help from all three of you who responded.