The Motor Spins and a New Layout
So, as mentioned last time, I had my Franken-prototype working again and I wanted to connect it up to a turntable motor to see if it will do as promised. I made a simple connection of just one sine output to drive the motor's AC cord as per normal capacitor configuration (single supply, cap generated shift). I connected it to a stock Ariston RD11 turntable. It worked! the single channel could drive the motor no problem. I left it connected for awhile to see how my small heat sink would do, it got kind of hot, so as I thought, a better heat sink will be needed.
|New PCB Layout|
Feeling happy and confident that the unit is working, I set out to re-design the PCB to include the added components and changes needed to fix my noise problems with the original PCB. The new PCB is slightly larger and I took care to layout the sections differently. The power supply is closer to the op-amp sections, the transformer hookups are all along the back. I think this layout is better but the PCB is larger, now measuring 5x5 inches. I also took care to increase the size of all traces carrying the power rails and the outputs from the op-amps. You can see a picture of the 3D mock up of the PCB included here. Also designed a small PCB for the front panel buttons and the RPM indicator LEDs (the fab house had a really good sale price for 5cmx5cm boards).
|Button / LED Panel|
So designing this new PCB was fun, it took some time as I tried being very careful with all traces, layout and hole sizes. Now I just have to wait for them to come back from the fab house, and that is the hard part.