I think maybe one for Crossey....

 

Have electrical earthing problems in the home we are renting. Loathe to spend any money or altering stuff too much as not my home.

The issue is unless everything is grounded, get some electrical hum from my guitar amplifiers, and worse get a shock through my guitar metalwork. Not a bad shock but a little more than a tingle. I have eliminated this largely now buy using 3 pin extension outlets and 3 pin plugs on all my gear. No noise, no shocks.

 

I recently got a new guitar amp from Japan which is 100V so need to use a transformer / adapter which unfortunately is only 2 pin plastic enclosed. No shocks as I guess the transformer is isolated between the primary and secondary windings but still getting some noise and hum. I will get an electronics guy I know to replace it with an internal transformer but how should it be earthed / grounded? Do I just connect the active and Neutral to the Trx and connect the earth to the metal frame of the amp? or does the transformer metal laminations need earthing too?

 

Bye the way, I do have a transformer rated at 230 / 115V 300VA. The amp is rated input voltage 100 volt. 70 watt. Would that do the job? I think power here around 220v + - 10% so would the drop in primary voltage equate to a drop in secondary output?

Does the amp have a specific grounding point amongst the connections? 

 

Assuming not I'd kick off with simply grounding the metalwork of the amp and see how you get on. It might be worth turning the 2-pin plugs around (try one at a time).

 

EDIT The change in output from your transformer input going 230-220V would only change the output from 115-110V still over voltage (and the Tx will likely start out high anyway).

 

3 hours ago, Crossy said:

Does the amp have a specific grounding point amongst the connections? 

 

Assuming not I'd kick off with simply grounding the metalwork of the amp and see how you get on. It might be worth turning the 2-pin plugs around (try one at a time).

 

EDIT The change in output from your transformer input going 230-220V would only change the output from 115-110V still over voltage (and the Tx will likely start out high anyway).

 

Do you mean does the Trx have a specific grounding point? I know the amp does. The amp already has a 3 pin input so I could ground the Trx and run a 3 pin out of that into the amp socket. I will either buy a transformer to fit internally and make sure it has some sort of earth lug on the laminations at least or buy a standalone metal cased Trx as in the photo which will have or I can make a grounding point. 

 

Do you think the transformer I showed you would be ok or too much overvoltage? It is an older guitar amp. Don't want to ruin it. I always thought Japan and US voltage the same but apparently not

12 minutes ago, Kenny202 said:

I know the amp does.

 

I actually meant the amp, with it's ground point to your common ground do you still get hummmm?

 

I think running it on 115V may be too much.

 

Autotransformer, as it reads on the shield, has usually the primary and secondary winding not isolated.