I have a Hammond Manufacturing 169TS Shielded transformer. What is the difference between shielded and unshielded (in laymans terms) and is this good for a basic method of isolation where a scope might be used on a stereo receiver or similar devices?
The green wire is connected to the shield and I would assume this would attach to the chassis of the box I put it in?

 

I have a Hammond Manufacturing 169TS Shielded transformer. What is the difference between shielded and unshielded (in laymans terms) and is this good for a basic method of isolation where a scope might be used on a stereo receiver or similar devices?

A shielded transformer such as the 169S series includes a metal foil barrier between the primary (input) and secondary (output) windings. This barrier, or shield, when grounded prevents noise on the mains from being coupled through to the output and can allow better performance in equipment which is sensitive to noise. It doesn't have anything to do with the isolation per se; the transformer itself takes care of that because there is no electrical connection between the primary and secondary winding.

This note from Hammond, though a bit technical, describes the effect of shielding.

The green wire is connected to the shield and I would assume this would attach to the chassis of the box I put it in?

Yes.

 

The transformer windings provide galvanic isolation between the input and output.
The shield provides capacitive isolation between the input and output.

 

So in effect, this would serve as a good isolation transformer on a hobbyist workbench?
Another question I have is to do with GFCI receptacles. Are they better than an isolation transformer or worse and can they be used in conjunction with an isolation transformer? If not, why? Thank you in advance and thank you for your previous answers.

 

So in effect, this would serve as a good isolation transformer on a hobbyist workbench?

Yes.

Another question I have is to do with GFCI receptacles. Are they better than an isolation transformer or worse and can they be used in conjunction with an isolation transformer? If not, why?

An isolation transformer prevents you from getting a shock if you touch one of the transformer outputs and are in contact with earth ground.
A GFCI will not prevent the shock but shuts off the power before the shock can kill you (which can still be nasty as I've learned from experience ) or likely damage your equipment.

So I leave it up to you to decide which is best for your purposes.

A GFCI can be used in conjunction with an isolation transformer but it's sort of a belts and suspenders approach.