PSU2 - Power Supply Unit for DIY Synthesiser Systems

Constructional difficulty: Moderate if using a low voltage AC output mains adapter.

A completed issue PSU2 board. This one is powered from an internal mains transformer so has the switch terminals linked out.

The Oakley PSU2 is a dual output +/-15V power supply based around the LM317 and LM337 regulators that is perfectly suited to powering a small to medium sized Oakley modular. Final output current capability is dependant on AC power source, the choice of smoothing capacitors and the heatsink used. However, with a suitable heatsink, capacitors and power source the Oakley PSU2 has been tested successfully at up to 1.2A per rail.

The PSU2 module must be fitted to a suitably large metal panel to act as a heatsink for the two power devices.

It is designed to work with our Dizzy and MU-Dizzy power distribution boards but can be used with other distribution systems if desired.

For safety reasons it is expected that the unit will be used with a external centre-tapped linelump (mains adapter) like the Yamaha PA-20 or PA-30. The PA-20 will allow the PSU module to provide up to 520mA per 15V rail, while the PA-30 will supply up 780mA per 15V rail.

Greater current outputs can be supported when used with an appropriate transformer or line lump, and suitably large heatsinks. The board will support mains transformers with either twin or tapped secondaries.

A component level mains transformer should only be used if you know how to connect high voltage wiring. On no account should this project be powered by a component level mains transformer if you are not familiar with fusing, earthing and safe connection of high voltage equipment. For safety reasons Oakley Sound can only endorse using this module with a low voltage input, such as the Yamaha PA-20 or PA-30.

The power supply uses standard parts throughout and requires only a simple voltmeter to set up. The circuit board takes less than an hour to build.

Various options are available for different types of switching, earthing and power on indication. The strong glass fibre PCB is silkscreened for easy component identification. It uses generous pad sizes, through plated holes for easy soldering and wide copper double sided tracks for reliable operation. The two layer PCB is 133mm x 76mm.

Chunky screw terminals are used for the PSU2's output connections. M4 ring terminals are crimped onto the connecting wires.

Power Supply for 19" Racks

A PSU2 module with internal mains transformer mounted to a 5U high panel at the rear of a 5U high 19" rack case.

The PSU2 module can be mounted to a 4U or 5U high 19" blank faceplate. These blank panels are available from various sources and are typically made from 2.5mm or 3mm thick black anodised aluminium so are easy to drill. The panel would be normally fitted to the rear of your modular's 19" rack case. Because of the generous surface area the panel acts as a very good heatsink. This design is suitable for connection to either the PA-20 or PA-30 power adapters for supplying currents of up to 0.52A or 0.78A per rail respectively, or, if you know what you are doing, fitting a mains transformer and appropriate switch, fusing and inlet socket.

Up to two Dizzy boards can be fitted to such a panel alongside the PSU2 module.

An original Oakley PSU module and single Dizzy PCB mounted to a 4U high panel at the rear of a 6U high 19" rack case. Raw power is supplied via a PA-30 line lump supply that connects to the three way socket seen on the right hand side of the panel. The green 4mm banana plug connects to the PSU's 0V connection to tie to other modular cases.

Project Downloads

PSU2 issue 1 Builder's Guide

Construction Guide Our handy guide to building Oakley DIY projects

Parts Guide Our handy guide to buying parts for Oakley DIY projects

A nearly complete PSU2 waiting to be fitted onto the panel and its two regulator ICs.


Click here for ordering details. 

PSU2 issue 1 PCB .................................................. 17GBP

3-pin power socket for external PSU ...................... 2.50GBP

All of the other parts should be able to be purchased from you usual electronic component supplier. Please see the Builder's Guide for more details.

See the Oakley Sound ordering page for ordering information, shipping charges and payment methods.

All prices include VAT at UK rates. Shipping/postage is additional to these prices. See also the FAQ page.

The three pin power socket for use with external PA-20 and PA-30 power supplies.

An Oakley PSU2 module connected to a single Dizzy board and mounted on a 5U high 19" panel. Note the grounding bond and 4mm socket to the right of the Dizzy board.

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Copyright: Tony Allgood.
Last revised: November 17, 2023.