When my mother was 10 years old, my grandfather purchased a rotating tree stand. They don’t make them like this anymore. It’s sturdy cast aluminum with a brush contact for powering the lights, and strong enough to rotate a real tree. It ran for 56 years, but last year when I turned on the lights, it wouldn’t make a full rotation without throwing the house circuit breaker. Pictured below is my Karosel Model R-100-B manufactured by the Kresky Manufacturing Company.
I opened it up and performed an inspection:
Pictured above are the scorch marks on the original circuit board.
Pictured below is the stationary base. It has two prongs conducting 120V from the wall into this circuit board that glides across the tips of the prongs. The circuit board then passes the current onto the electrical sockets on the outside of the stand.
The base had bent in over the years, allowing the circuit board to brush up against the bottom-most prong. This caused a short, and the resulting arc destroyed the board. With the prongs being in good condition, I focused on replacing the burned circuit board.
A set of calipers was used to measure the width of the concentric rings. Using the measurements, Phil Showers helped me create a design in Inkscape:
I took a piece of copper clad board and spray painted it black to create a base for a mask. Using the shop’s desktop laser cutter, an inverse of the image was rastered onto the painted board. This burned the parts of the unwanted mask away.
Pictured above is the board after one pass in the laser cutter, and below after the second pass:
Once out of the laser cutter, I used the shop’s scroll saw to cut out the board and the belt sander to smooth out the edges. Then, using a sanding paste, I removed the remaining mask that the laser cutter wasn’t able to burn away:
At this point the board was ready for the acid bath:
The acid is a mixture of hydrochloric acid and hydrogen peroxide. After about 30 minutes in the bubbler, anywhere the acid touched copper was eaten away. Anywhere the spray paint mask remained protected the copper underneath. This left behind the concentric conductive rings on the board.
In the next picture you can see the board with its exposed copper removed. Next, the remaining spray paint was removed using paint thinner and manual scrubbing with a household sponge.
The original board was used as a template to drill holes in the new board. I was able to salvage the original electrical connectors and mount them on the new board. I didn’t have copper riveting equipment, so I used zinc plated #4 machine screws and nuts.
Below is a picture of the new board mounted on the stand. I added some solder between the screw and the board to increase conductive surface area between the two components.
Although it has been used to hold live trees in years past, I have an artificial tree in mine 🙂 Live trees are a mess.