As part of a project that involves a complete makeover of a Fons CQ30 turntable, I want to rebuild the power supply. The components are all ancient and the shape of the PCB is odd. No doubt this is due to its place in the turntable's enclosure, but i want to move it to a separate box. The elco on mine is most certainly dead.
As a noob (both to this forum and to diy audio) I wouldn't be able to do so if it weren't for the enclosed schematic I found over at Vinyl Engine. So a thank you to them.
Before I embark on making a new pcb from this schematic, I want to ask the open question: can any of the folks here with turntable expertise recommend straightforward ways for improving on the design of this power supply or the choice of components? (Without starting over with a blank piece of paper.) Anything that can improve the stability of the speed control for example. And I haven't checked but at least some of what is listed here must be obsolete.
The only choices I have made are the easy ones: a rotary selection switch for the speed selection, and new (rotary) potentiometers for the pitch adjustment. I plan to replace the motor with a NOS unit from a Philips GA312 I ran into recently, as mine requires some manual help to start spinning. Apparently these are are a drop-in replacement for the CQ30's motor (unlike the Philips GA212's motor, which are easier to find but makes the platter spin at around 150RPM without adjustments).
All advice would be much appreciated.
As a noob (both to this forum and to diy audio) I wouldn't be able to do so if it weren't for the enclosed schematic I found over at Vinyl Engine. So a thank you to them.
Before I embark on making a new pcb from this schematic, I want to ask the open question: can any of the folks here with turntable expertise recommend straightforward ways for improving on the design of this power supply or the choice of components? (Without starting over with a blank piece of paper.) Anything that can improve the stability of the speed control for example. And I haven't checked but at least some of what is listed here must be obsolete.
The only choices I have made are the easy ones: a rotary selection switch for the speed selection, and new (rotary) potentiometers for the pitch adjustment. I plan to replace the motor with a NOS unit from a Philips GA312 I ran into recently, as mine requires some manual help to start spinning. Apparently these are are a drop-in replacement for the CQ30's motor (unlike the Philips GA212's motor, which are easier to find but makes the platter spin at around 150RPM without adjustments).
All advice would be much appreciated.
Philips used regulated power supplies on their turntables using this motor: e.g. GA222, GA312, GA406 etc. Some versions of the FONS PCB have designations for ZD1 (I'm guessing it was for a 9V1 Zener diode) although it was never implemented - there was no series resistor.
CORRECTION: At the time of reverse engineering the FONS circuit, I had no idea that Philips made the GA406 (I had only just discovered that the FONS used a PHILIPS motor). The FONS circuit is based on the PHILIPS GA406 circuit.
If I was upgrading the control circuit, I'd use a regulated supply and install the tacho clamp diodes (D408 & D409) and possibly some of the electronic speed selection from the GA222, GA312 etc. I'd also stick the fuse (T<250mA) on the primary side of the transformer.
Good Luck!