Taking Shape

The transformers and a few other parts from Weber came in today. I had to go to the Weber website to get the schematics for the transformers, as they weren't included in the shipment. There are a few changes in wire colors from the original Vibro Champ's trannys, but by comparing the schematics for both, I figured out which wires are which. There will be a few extra wires on the power transformer that will need to be clipped and taped off. These extra ones are for alternate input and output voltage configurations.

Also from Weber, I received the multisection electrolytic capacitor, or Cap Can. I am very impressed by the build quality of the components from Weber.

In order to transfer my drawings to the metal, I cut a strip of graph paper at actual size, drew the hole locations on it, and then used that to mark on the chassis. I was sure to make the drawing on the strip a mirrored image, since the original hand-drawn plans were a view from inside the chassis and I was cutting from the outside. This method seemed to work pretty well, and it was easy to get the chassis to look like my sketches.

Before cutting I placed the components on the chassis just to get an idea of what it will look like once complete. By doing this, I was making sure the tubes weren't going to be too close to one another or the Cap Can. After some last-minute tweaking and slight repositioning of a few holes, I was ready to cut.

I decided not to use a UniBit to drill the large holes for the tube sockets and Cap Can. Morgan Jones' book recommended not using a bit on a hole larger than 1/2 inch, stating that anyone trying to do so "is just asking for trouble." Rather, I used a unique tool called a Nibbler. It takes quite a while to chip away at the sheet metal, but it is very controlled and leaves a clean edge. I used a 11/32" bit to make the starter hole, then there is enough room to get the Nibbler in and cut out the appropriate hole. Of course, I filed down the edges to smooth them out as best as I could afterward.

After getting all the holes cut, I tackled the holes for the power transformer. The larger rectangular hole took quite a while to cut, and I recommend using padded gloves if you are using the Nibbler for a prolonged period of time. I used fingerless mountain biking gloves, which kept my fingertips free for fine detail work. 

You might notice in the photos that the output transformer is slightly elevated off the chassis. I lifted it with a few washers for two reasons: 1) to allow the output wires to pass underneath for a tidy look, and 2) to allow clearance for the heads of the turret board standoff screws. I used a rubber grommet as insulation/protection in the hole drilled for the output transformer leads.

I attached all the pieces I had drilled holes for thus far for a nice test fitting, and everything looks really nice. At last, this thing is beginning to look like an amplifier!

After mounting the big, heavy power transformer directly on the aluminum chassis, it became apparent that I should go ahead and use a piece of aluminum angle trim to brace from the inside of the chassis. While the project box is holding up the transformer now, it might not after several gigs and roadie abuse. There really is no reason not to make it as robust as possible, since it's easier to do that now rather than trying to go back and brace it later once the whole thing is completely wired.