Shielding in a head cabinet

[six el six]

I see shielding on the bottom of a lot of tube heads in the cabinet. Is this a good idea and if so where do I get appropriate material to install shielding in a cab?

I don't see it in Doug's store.

[HotBluePlates]

What I've generally seen is either some very heavy duty screen or a some moderately thin sheet metal (of whatever material matches the chassis). Dissimilar metals could lead to some corrosive effects.

You might find blank sheet metal panels from Hammond (through whatever distributor you buy their products from). I'd think you'd want something slightly bigger than the opening in the chassis, to ensure complete contact from the chassis to the shield plate.

[RicharD]

Home Depot sells foil tape in the HVAC isle.  It's cheap and conductive.

[HotBluePlates]

Home Depot sells foil tape in the HVAC isle.  It's cheap and conductive.

Have you figured out if the adhesive is conductive? That is, would you get continuity if you had to overlap several strips to cover the whole open side?

[JayB]

Get some flashing and staple that to it.

[sluckey]

Have you figured out if the adhesive is conductive? That is, would you get continuity if you had to overlap several strips to cover the whole open side?

Good point. I just rechecked my TDR amp. I had put HVAC AL duct tape on my back panel. I used two strips of 3" wide tape with a 1" overlap the full length (≈ 17"). I had good continuity between the two strips measured at many different locations.

You can also get adhesive copper foil.

[stingray_65]

Get some flashing and staple that to it.

+1

I picked up a roll pretty cheap a while ago and use it all the time. It was a squashed roll at the Lowes and they couldn't sell it except as damaged goods.

The adhesive you use for your tolex will hold this stuff in place really well.

If you go the tape route (I have), don't worry about the over lap. the chassis should contact each strip and make good contact for a simple shield.

Ray

[RicharD]

>Have you figured out if the adhesive is conductive?

Pretty much what Sluckey said.  When I first thought of this, I did some tests and had good conductivity through the adhesive. The biggest issue is connecting the chassis to the tape.  My first project where I used foil tape, I used a wire with an O ring crimp and a short wood screw.  It was not a slide in/out cabinet so this worked fine.  What I did on the slide in/out cabinet was run a band of foil tape down the side and passed it over where one of the chassis bolts goes.  Hard to gauge the integrity of the connection since when all closed up, you can't get probes in there.  One would assume something is better than nothing.  Foil tape is probably not the best solution but it certainly is an economical solution.

[mresistor]

I love that 3M foil tape - for many different uses.... and probably some I don't know about yet.

[six el six]

Thanks everybody.