The weakest link in the Prophet 5 synthesizer is the power supply. It’s a very basic supply, however runs all the voltage regulation on very high un-regulated voltages. The 5V rail in particular is regulated a whopping 23V down! What this can cause is primarily a lot of heat to be dissipated. This is why the Prophet runs so hot. Secondly, the Prophet has a greater chance of lock up.. If too much heat is generated, the 5v regulator goes into protection, which will crash the system. Additionally, the original transformer causes the unit to physically vibrate which can be very annoying.
Enter our new PSU assembly. It utilizes a 2 bridge rectifiers and 2 transformer secondaries bringing down the pre-regulation voltage tremendously. This means the supply is working much more efficiently, and less heat will need to be dissipated. This will keep the oscillators in better tune, and also tremendously lessen the chance of lockup.
Other Prophet 5 supply replacements try to simply manipulate the heat sink configuration. This is a bandaid to the real problem. Our’s replaces both the original supply PCB and transformer and fits with the original heatsink, which is adequate.
- Axial capacitors instead of large computer screw-in type. The old screw-in caps usually measure about 2100uf now a days instead of the 6300uf they’re rated at. Additionally, they’re hard to find in the right size and very expensive when found ($80 per cap sometimes!) Axial caps won’t be going anywhere anytime soon
- Multi turn trims with vertical trimming. This makes trimming it much easier and more precise. No more latex paint to hold the trimmer in place!
- Test points! To measure voltage on a stock supply, you need to probe wire pads that are strikingly close to ground and other parts of the circuit. A small slip of your probe and it’s smoke time! Our’s features separate holes with test point loops installed, making it much safer (and easier) to probe the supply voltages during calibration
- Mounts just like the original! Regulator are bolted to the heatsink with average hardware (included) and the whole supply mounts where the original capacitor mounts go. All wires go into the same places.
- True and linear supply. Switching supplies are a popular buzz word in the vintage synth market. Linear supplies are still the best for reliability and design implementation. Switchers can be noisy, sketchy, and are a kludge to install. Plus, when they break, you probably won’t be able to fix it.
- Assembled PCB with brand new components. No surplus or rare parts.
- New, quiet transformer with hardware to mount where the original does
- New primary voltage selection switch. This isn’t needed, but makes installation much quicker
- Mounting hardware to mount the new PSU using the holes from the mounts that held the original supply down by their capacitors.
- Directions for installation. This is not a mod to be installed by the end user. You should use a tech.
- New EPROM for your revision. This is needed if you’re running a Rev 2 (with or without cassette) or Rev 3.0 (not 3.1 3.2 or 3.3) which use 2708 type EPROM. This supply does not bother with the -5V or +12V rails that plagued those supplies with unreliability. With a simple ROM change and small circuit modification documented and implemented by Sequential when the Prophet was in production, these rails are not needed.
- New capacitors for rest of unit