Line a Guitar Amplifier Chassis to Reduce RF

I did this instructable at Techshop Detroit.
The website for Techshop can be found here:
www.techshop.ws


For this step in my multi-part instructable, I will be modifying the chassis to fit the input jacks, and the lining the interior of the chassis with copper. I purchased the foil from Stewart MacDonald. (www.stewmac.com)  I purchased the 3pack of tape sizes which made this project much easier.

I decided to put copper foil on the inside of my amp chassis for two reasons. First, to reduce the amount of RF that could creep into the signal. Second, to ground the potentiometers and jacks that are located on the front of the amp. Without this foil, I would have to run a ground wire to each and it would not have looked nearly as cool.

This chassis is from the 1940's and had an old radio circuit in it. I tore all of those guts out and made a new chassis to hold a guitar amp circuit. You can find the earlier steps in my other instructables.

I took everything down to the wood. I wanted the interior to look neat, so I made sure to remove everything that will sit on top of the foil.

This picture is with everything still in the amp.

It was at this point when I realized that I had not left enough room for the input jacks, and that they were contacting the metal chassis. I decided that the best way to move forward was to notch the metal. This will leave a neat clean appearance on the front of the amp. Not exactly perfect, but hey... It's hand made!

This is one of those bonus steps that you try your hardest to avoid. I first marked off where I needed to cut, and then used masking tape to make a "do not cut" line.

I used a Dremel and a small cutoff wheel to notch the chassis. If I were ever going to make this exact amp again, I would just design this notch into the chassis and have the waterjet do the work. Oh well!


After cutting out the notch, I used a flat file to clean up the edges.

Ok, At this point, I was very eager to apply some foil. I had three widths to work with. I used the one inch roll to start on the front face. It is important to not allow the foil to touch itself. It's really sticky (and expensive!)

I used a plastic scraper to burnish the foil onto the surface. This will allow it to adhere for a long time.

After using the one inch width stuff, I went back and filled in all the little gaps with the half inch stuff. It gave it a nice professional finish.

I used the 3 inch wide roll to cover the large surface of the floor and walls. Again, I used the half inch roll for the gaps to get that finished professional look.




Tune in next time as I make a logo out of plexiglass (that lights up!) and do the final assembly. Hopefully I will be playing soon...