Old stereo Power concerns

[sr1200]

A buddy of mine has an old stereo receiver (talkin 70s vintage) that has a 2 prong plug (US voltage and plug style) that doesn't seem to be polarized (one prong bigger than the other).  I would like to put a grounded cord/plug on this thing for safety, and was wondering if there is any consideration for the polarization of the plug itself.  As in, is there a correct way to rewire this to the fuse/power trafo that I should follow.  Also, since there was no chassis ground on this previously, would there be an issue with adding a chassis ground to the unit.  I can take some pics if needed.  Thanks.

 

[PRR]

Get the Green Ground to the chassis.

Don't fret the White/Black.... 33% chance his outlets are wired wrong (60% in my old kitchen).

These 2-prong stereos didn't kill a lot of people. Perhaps they were all used on wood floors? (But also a lot of basements.)

Note that this is *different* from Guitar Amps. The guitar player HOLDS the chassis-ground for the whole set, and puts his lips on a PA ground which is often different. He's also under performance pressure. The stereo use touches the system rarely, and is liable to notice the least shock and investigate.

 

[dmp]

the small prong (black) is hot and should go to the fuse.

If neutral is fused and hot shorts to the chassis, the fuse provides no protection.

 

[JohnRoberts]

What PRR said. Primary should be double insulated so safe either way.

You might squeak out some tiny benefit from trying both ways while measuring the noise floor.

Check inside for a stinger cap, from one of the hot legs to ground. Most consumer products don't use them but I have seen a few inside VCRs. While those VCRs were probably later models with polarized plugs.  The small stinger caps can do more harm than good in unbalanced systems.

JR

 

[sr1200]

Thanks for the replies, much appreciated.