Dbx 160/161vu safety ground

[Electrobumps]

Hi

I had Jim williams Mod my 161vu to balanced and rewire the mains for 240v and do his tweaks. Left the 160vu as stock. I'm in the UK 240v and both units have no safety earth. I don't really like this as its a metal chassis and want to ground safety earth directly from the electrical earth to the chassis at point of entry of the power cable. Safety wise a good idea, but anyone know of any potentially issues or a different way this should be done on these units?

These were a bit beaten up when I purchased on Ebay many years ago. I'd love to get my hands on one power and one meter switch and missing a single switch cap. Spent a lot of time looking online but no luck.

thanks

 

[abbey road d enfer]

Hi

I had Jim williams Mod my 161vu to balanced and rewire the mains for 240v and do his tweaks. Left the 160vu as stock. I'm in the UK 240v and both units have no safety earth. I don't really like this as its a metal chassis and want to ground safety earth directly from the 3 pin to the chassis at point of entry of the power cable. Safety wise a good idea, but anyone know of any potentially issues or a different way this should be done on these units?

Beware that the mechanical construction of these units does nor result in good electrical conduction between its dofferent parts. I would recommend adding at least one wire from the ground lug on the rear panel to one on the front panel.

 

[JohnRoberts]

I am speculating, but the primary function of EGC (equipment ground connection) is to shunt stray mains voltage to ground with low enough impedance and long enough to trip fuse/circuit breakers. If the transformer is screwed/bolted to the chassis, that seems like a good place to attach the line cord ground lead. A secondary function of EGC is capturing rogue hot voltage stingers coming in through shields or audio grounds from other hot chassis SKUs.

I just found a picture of dbx 161 on the WWW, looks like the steel side/rack mount might be a good low impedance chassis node. I don't see any transformer attachment screw/bolts going through the chassis so good luck with that.

The mechanical package design may be a concern with ground integrity. I recall last century performing ground bonding tests for UL approval where the safety ground path had to carry tens of amps with only single digit voltage rise.

A final concern is pin 1 noise rejection (edit- no pin 1 on 1/4" I/O, hopefully TRS. Sleeve =pin 1). I will ASSume JW used a high performance balanced audio input circuit.

Just to be clear, you are not talking about balanced power, but balanced audio I/O? The picture I found on the WWW looked like dual mono with two separate 117VAC line cords. One might cleverly just connect the two 117VAC transformer primaries together in series. The 60 Hz transformers might be marginal at 50Hz but probably OK.

Of course any hot primary wiring should probably be double insulated (sleeved).

JR

[edit- of course don't trust free internet advice about mains power wiring safety. /edit]

 

[Electrobumps]

Thanks for the comments. This is purely a mod to improve safety incase mains voltage reaches chassis. Sorry that first post was written poorly and now updated.

The JW mod unit was changed to 240v and the 160vu stock is 120v. There is information on the windings in a service manual which I have read before but will need to refer to this.

Good plan to link front and back chassis for continuity.