I came across a used Pittsburgh Modular Cell 90 Eurorack case with a Tiptop Audio uZeus power supply included, for a very good price. I couldn’t resist. I already have two other Cell 90 cases with upgraded power. The uZeus is designed for and comes with flying bus cables, which were included. Though I could have used them, I prefer a bus board. So I went shopping for a passive bus board and found this one by Tiptop Audio, that has a +5 volt regulator onboard. But, the uZeus also has +5V.

Handling the 5V supply

Both the uZeus and the bus board have 7805 type regulators. The one on the bus board – in addition to being brand new – was a little better. In fact the power specification for the 5V rail on the uZeus is 170ma, and the one on the bus board is rated 220ma. The bus board has a nice screw terminal strip for connecting up power from a supply. It even has an input terminal, VR, for the input to the 5V regulator. Hey, the uZeus has a VR output! It comes out of a chip. I measured this at 15 volts. The idea is to avoid having the 5V regulator driven from the +12V regulator (even though the manual for the bus board tells you to do this). All I needed to do was to remove the 5V regulator from the uZeus and run the VR line over to the bus board.

The ground banana jack

I always add a banana jack to my cases, so that they can be all grounded together and also to work with banana jack gear.

The power inlet and switch had been removed from the Cell 90. I reused the inlet hole to mount the ground jack, using some washers because the hole was a tad too big. The hardest part of this project was drilling eight holes in the steel case to mount the bus board. I recommend using cobalt drill bits for steel.

I used a short, 16-pin power cable to go from the uZeus to the bus board’s first header. The 5V line comes back into the uZeus to light up the 5V LED.

I hooked up one of my 15 volt wall adapters through an adapter cable to convert from the 2.1 mm plug to the 2.5 mm inlet. Both sets of LEDs light up, as expected. I suppose I could remove the ones on the bus board, but I wanted proof here, and they don’t use much power.

BTW, I installed J7 on the uZeus, which provides some load to the -12V regulator when there is a small or non-existent external load.