Moog Rogue: replacing the power supply
The Rogue’s original power supply is not ideal. It uses an external transformer in a box with one cable going to the mains, and another cable plugging into a 3.5mm headphone-style minijack on the synth. The minijack delivers a nominal 24V AC, which is then rectified into +12 and -12V DC internally. The power switch on the synth simply connects/disconnects the AC input at the jack.
When I received my Rogue, the transformer was damaged. Rather than buy a replacement, I decided to install a power supply inside the body of the Rogue. There is plenty of room to do this safely.
NB: I take no responsibility for anyone’s actions regarding mains electricity. If you are not confident working with it, don’t. Hand the job to someone qualified.
First job was to desolder the power inlet jack, and solder two wires to the place where the jack was on the main PCB. Unfortunately, the photo below is the best I have at hand. Note the two red wires supplying low-voltage AC:
These two wires go to a connector that allows one to plug or unplug from the transformer for ease of maintenance. There are several kinds of connector that would work; I chose the type found in computer power supplies, as it’s what I had in the spares box:
The other part of this connector goes to the low-voltage AC output of a transformer. The service notes state the Rogue requires 24V AC at 200mA. I leave selection of a suitable transformer up to you. Note that the Rogue’s rectification is provided by a 78M12 and a 79M12. I used a twin-secondary 12V (with the two 12V secondary windings wired in series to give 24V) rated at 12VA – the Rogue is rated at 6W. Again, I am not taking responsibility for the safety of others here, only providing an outline of my own process.
The transformer is bolted to the base plate of the Rogue. An earth lead is connected to one foot of the transformer:
From the transformer’s mains-level connections, wiring goes to a newly-added mains inlet. I chose the clip-in type with an internal switch and fuse. I cut a rectangular hole in the rear of the Rogue, set low down so as not to interfere with the graphics, which also meant trimming a little of the base plate’s rear lip.
Here is an overview of the result, with tape to secure the looser wires:
Here is the result from the outside:
My Rogue also came with a plug to stop up the hole left by removing the power jack:
I tend to use the mains switch on the rear, and leave the panel switch set to ON. It would be a simple job to remove and bypass this, but I consider it unnecessary.
EDIT IN RESPONSE TO A COMMENT: I used a 250V/0.25A fast fuse in a built-in fuse holder in the panel-mounted inlet, which is in addition to the fuse in the UK mains plug. This is a higher current rating than necessary, but it was the lowest I had in my parts box at the time. I have seen two other examples using 120V/0.1A and 120V/0.2A respectively. Your choice of fuse depends on your local mains supply voltage, and you should always select a fuse rated for that supply (eg. nominal 240V here in the UK, 120V in the US, etc.). The current rating should allow enough room for the synth to power up and operate without blowing it. The Rogue is rated at 6W, which works out at 250mA at 24VAC. If we translate that to 240VAC, this drops to a mere 25mA. At 120VAC, it would be 50mA. In either case, a 100mA fuse should be OK.
I’m not going to justify what I now consider rather scruffy wiring – suffice to say that I did this mod three years ago, and would take more care over it these days! However, as it stands this mod has never given a moment’s trouble. I’ve since been in and tidied it up a little.
(2nd April ’18)
MAINS ELECTRICITY CAN KILL OR SEVERELY INJUR. PLEASE NOTE THAT SAFETY MUST BE PARAMOUNT. IF YOU ARE NOT CONFIDENT WORKING WITH MAINS ELECTRICITY, GET SOMEONE QUALIFIED TO DO THE WORK FOR YOU.