The new PS-7 power supply board is only 2 by 3 inches big. Yet it can pack a punch, as it holds two 47µF/450V capacitors. In other words, it can be used to make a power supply up to a 400Vdc.
The circuit is extremely simple, with just 18 components: four rectifiers, five resistors, and seven capacitors. The PS-7 can also be used with a center-tapped transformer; just attach the center tap transformer lead and leave rectifiers D3 & D4, resistors R3 & R4, and capacitors C3 & C4 off the PCB.
Capacitors C5, C6, C7 and resistor R5 define a simple RC filter that helps smooth away ripple. Resistor R5 can be replaced by an external choke (inductor).
The lower the DC output voltage, the bigger capacitors C5 & C6 can be. For example, if we lower the secondary voltage to below 130Vac, then we can use 220µF/200V capacitors, which offer four times more capacitance over the 450V capacitors. And if we lower the secondary voltage to below 36Vac, then we can use 1kµF/63V capacitors, which offer twenty times more capacitance over the 450V capacitors. If the current draw remains constant across these three voltage options, the ripple will fall with each increase in capacitance.
Who would need such this high-voltage power supply? I do, for one, which is why I designed the PCB. I found myself often needing a small power supply to add to existing electronic gear or new projects, but I hated having to point-to-point all 18 parts on a terminal strip, even though I am good at this task.
Where is the heater power supply?
There isn't one—well at least not on the PCB. Many power transformers intended for use in tube audio gear are woefully weak in heater winding current, which precludes using them to power a DC heater power supply. Here is an example, a 6.3Vac @ 1A heater winding cannot deliver anywhere near 1A of DC current at 6.3Vdc. When using such a transformer with a 1A load, it's best to give up on using DC and settle for AC on the heaters. In addition, there is an AC-heater fan club out there, making the PS-7 just perfect for its members. Does not include power transformer.
Kit includes a user guide and all parts needed to populate the PCB. All the parts, like the PCB board itself, are of the highest quality (Panasonic polypropylene and Nichicon electrolytic capacitors, ultra-fast rectifiers, many 1W carbon-film and 3W metal oxide resistors, and ceramic capacitors.