DIY PSU for Boss mini-racks

In the eighties, Boss marketed the Micro studio series, a bunch of half-width 19" rack mount effects. There were nine : the RBF-10, RCE-10, RCL-10, RDD-10, RGE-10, ROD-10, RPH-10, RPQ-10 and RSD-10. Because they don't have a voltage regulator inside, those units are not to be used with an ordinary wall wart. Boss expect you to use their special PSU instead (PSA-120 / PSA-220 / PSA-230 / PSA-240), which I believe to be nothing more than an ordinary wall wart with a voltage regulator.

Adding a 9 V voltage regulator to a wall wart is not difficult. You need :

Attached the heat sink to the cover. I had a TO-3 heat sink with four holes so I threaded tapping screws through three of the holes and into the cover. I took great care to avoid any possibility of electrical contact between the heat sink and anything inside the wall wart. A screw touching a live wire could prove fatal to the gear and the people around it.

side view front view inside view

Removed the voltage and polarity selection switches. Instead ran wires straight from the PCB to the 7809. Picked the lowest voltage available that was at least 2 V above 9 V (in this case, 12 V).

This wall wart has been powering an RBF-10, an RCE-10, an RCL-10, an ROD-10, an RPQ-10 and an RSD-10 since around 1991 with no problems. In 2007, the smoothing cap finally dried out and had to be replaced. The replacement was too large to fit in the case, hence the big cream-coloured lump at the base of the cord.

Yes, I have neglected the Vin-to-ground and Vout-to-ground capacitors recommended by the 78xx data sheets (Motorola/ON, ST) but I've been lucky and it seems to work well enough.

 Danger sign   WARNING — This document describes potentially dangerous operations that could destroy equipment or kill people. I could be wrong. I could be lying. You are responsible for your own safety.   Danger sign 

This is, last updated AYM 2015-02-23.