where to buy thin cardboard with aluminum backing to shield open side of chassis.

[mikepukmel]

Hi All, anyone know where I can buy a sheet of cardboard with aluminum cladding that they use in amps to shield the open side of the chassis? If I cant find that, I was thinking about going with a thin thin piece of sheet aluminum or brass, although both I think have a reaction with the steel used in Fender type amps.
Thanks
MP

[Tom Phillips]

I say that there is no need for the cardboard layer. For home builds, or when a customer is not concerned about period correct looking stuff, I just contact glue heavy duty aluminum foil to the wood cabinet where the open chassis rests. If done well it is unseen and very low profile with little chance of catching on the chassis and being torn up during service work. By the way, the BF Fender amps utilized a stapled in place piece of steel window screen. I once saw a really goofy mistake by wanna be cloner who used black nylon window screen.

[mikepukmel]

Thanks Tom. I have some fairly thick aluminum tape, pretty good quality used for heating and air conditioning. Also have some leftover aluminum windows screening. Easier to put the tape on. Thanks for the info!

[mikepukmel]

Oh man, black nylon window screen. Heh. I bet you got a nice laugh out of that.

[Tom Phillips]

Best to use one continuous piece of whatever material you end up selecting.
1) Guaranteed to be continuous electrical connection
2) Minimizes edges that could catch on the chassis
My 2 cents anyway.
Tom

[J M Fahey]

I say that there is no need for the cardboard layer. For home builds, or when a customer is not concerned about period correct looking stuff, I just contact glue heavy duty aluminum foil to the wood cabinet where the open chassis rests. If done well it is unseen and very low profile with little chance of catching on the chassis and being torn up during service work. By the way, the BF Fender amps utilized a stapled in place piece of steel window screen. I once saw a really goofy mistake by wanna be cloner who used black nylon window screen.

Hey I bet no flies or mosquitoes flew through that one either, so what´s exactly your point?

As of cardboard backed aluminum, I use a lot of it, and make it myself, just contact cement kitchen type aluminum foil to business card thickness cardboard.
Overlapping aluminum glued together keeps good electrical contact, although contact rubber cement is an insulator, while relatively fresh (say, 15 minutes) it still allows aluminum wrinkles through so they touch the mating surface.

It may be glued-stapled to cabinet wood but being somewhat rigid I also build separations between preamp and power amp, small Faraday cages around input jacks, etc.

[mikepukmel]

Hey I bet no flies or mosquitoes flew through that one either, so what´s exactly your point?

As of cardboard backed aluminum, I use a lot of it, and make it myself, just contact cement kitchen type aluminum foil to business card thickness cardboard.
Overlapping aluminum glued together keeps good electrical contact, although contact rubber cement is an insulator, while relatively fresh (say, 15 minutes) it still allows aluminum wrinkles through so they touch the mating surface.

It may be glued-stapled to cabinet wood but being somewhat rigid I also build separations between preamp and power amp, small Faraday cages around input jacks, etc.

Thanks Juan, What do you separate your power supply sections with, and also what do you build your faraday cages with, if you don't mind me asking.

[J M Fahey]

Just what I said: aluminum covered (on one side only) with kitchen aluminum foil.

Way simpler than you think, I just cut needed separation walls out of it, leaving an 8 to 10mm flap which I can glue to chassis where needed, I can bend it to cover what I want to shield if I want, it´s automatically grounded when glued, for future amp servicing it can be bent out of the way or simply torn off and replaced later, cheap as dirt.

Today I am finishing a couple combos, a Guitar one and a Bass one, will post some preamp shield picture.

Adding separations in commercial amps is easy/cheap, they resistance solder them,


but on homemade stuff unless having an industrial resistance solder machine under your bed

you´ll have to add some kind of unsightly holes, either for riveting or plain bolting ... but since cardboard is so light, gluing becomes an option.

[mikepukmel]

Just what I said: aluminum covered (on one side only) with kitchen aluminum foil.

Way simpler than you think, I just cut needed separation walls out of it, leaving an 8 to 10mm flap which I can glue to chassis where needed, I can bend it to cover what I want to shield if I want, it´s automatically grounded when glued, for future amp servicing it can be bent out of the way or simply torn off and replaced later, cheap as dirt.

Today I am finishing a couple combos, a Guitar one and a Bass one, will post some preamp shield picture.

Adding separations in commercial amps is easy/cheap, they resistance solder them,


but on homemade stuff unless having an industrial resistance solder machine under your bed

you´ll have to add some kind of unsightly holes, either for riveting or plain bolting ... but since cardboard is so light, gluing becomes an option.

Ah geez, I just threw out my last 'spot' welding machine. Should have kept one, heh. Can't wait to see the photos.

***
The only aluminum foil we have is really thin. Going to the hated big box stores to see what they have. I dug out the aluminum screening I have but worried little bits will break off pulling the chassis in and out, and fall down in there and provide 'unwanted alternate conduction paths'.

Found 2" copper foil tape online for like 15 bucks. Maybe will try getting some really thick 'freezer foil' from Target and glue that the cabinet as you all have suggested.

[J M Fahey]

Kitchen foil is real thin, way thinner than printer paper, but if you glue it to cabinet wood itself, preferrably before tolexing so it´s "buried", no big deal.
That way it will not shed bits and pieces raining on the board.

Now if you have some sheet aluminum supplier available, they often carry (or can order for you) much thicker 0.1 mm (4 or 5 Mil" , guess #30 *aluminum* gauge, different from steel gauge) thick aluminum, so rigid and sharp that it can easily bleed you (don´t ask ), that´s the kind Fender/Ampeg and many others use, which is not glued but stapled.
An edge can and probably will bend, but it will definitely not crumble.

[R.G.]

Supply stores that provide heating and air conditioning (HVAC) supplies have thick aluminum tape with a profoundly aggressive adhesive on it in widths up to about 4". This is no kitchen aluminum foil. It's designed for sealing HVAC ducts semi-permanently. Once it's pressed and burnished into place, you generally have to destroy the tape to get it off. I've used it for permanent case shielding before.

And of course, I keep the roll handy for actually fixing my AC ducting.

[mikepukmel]

Cool, thanks. I actually have 1/2 a roll, didn't think it was good for this. I peeled a little off, put the meter probes on (just touched) and got 0.2 ohms! So, there's no coating on the exposed foil side. And its pretty thick as well. I put little pieces of wood in the combo cabinet so that I could slide the chassis in and out, so the chassis doesn't rub the top of the cabinet, so this will work, thanks.

[Chuck H]

But is the aluminum tape coated? I thought it was. Any coating would be an insulator against contact.

I use HD aluminum foil and contact cement. I do have a roll of aluminum flashing that is thin enough. I've tried stapling that in place like other amp makers. I didn't like it. After repeated chassis insert/removal operations there's always some snagging and bending. Just like other amp makers.

[Bill Moore]

My last build, I used copper tape to shield the back panel. Seems to work! (I guess I should mention that I also like to support the copper miners!)

https://www.amazon.com/dp/B01I1XNY1E...TJ7OelRE1E0kTw

[Leo_Gnardo]

My last build, I used copper tape to shield the back panel. Seems to work! (I guess I should mention that I also like to support the copper miners!)

What Bill said ^^^ and you may find you don't need to cover the entire panel, just the part that covers input & preamp circuitry.