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Updating old electronics with 3 prong plug

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fairchild

New Member
I've done some research on how to do this, but i have this old sony microphone pre amp that seems to have been originally wired up differently than other gear that i've looked at.

The original plug had one wire going to the fuse, which then went to the transformer. The other wire went to the on/off switch, and then went from the on/off switch to the transformer.

The original cable prongs were not polarized.

How should i wire up a new cable that has a ground cable...it's black, white, and green.

Thanks!
 

Sceadwian

Banned
Don't wire green...
 

fairchild

New Member
well, i probably would not have messed with it except for the fact that i'm having problems with input level. When i touch the chassis with my finger (with original wiring), the input level went up. I figured i would give this a shot to see if it solved the problem.
 
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Sceadwian

Banned
Generally speaking the ground wire is connected to the chassis. But considering the circuit wasn't designed with a saftey ground in mind the whole thing could explode if you wire it like that so proceed at your own risk =)
 

fairchild

New Member
"Generally speaking the ground wire is connected to the chassis. But considering the circuit wasn't designed with a saftey ground in mind the whole thing could explode if you wire it like that so proceed at your own risk =)"

This is why i'm here posting the question.
 

kchriste

New Member
Forum Supporter
The problem with connecting the green wire is ground loops. Ground loops will cause hum to be added to the audio. If the chassis ground and green wire can be isolated from the audio ground, then it can be made to work. Otherwise use a 2 prong plug.
 
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