Prophet 5 Rev 3 Replacement Power Supply

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synth80s
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Prophet 5 Rev 3 Replacement Power Supply

Post by synth80s » Tue Oct 29, 2019 2:09 am

Hi everyone, as some of you know I have shared some content of my prophet 5 after I spent many hours bringing it back to life after a tech butchered its restoration. I wanted to test the waters to see who would be interested in a newly engineered power supply. A friend of mine who has been a principal engineer for several decades designed and built a new supply for my prophet, which alleviates the issues with the infamous weak 5 volt rail. The prophet's transformer only has a single winding, which outputs 22 volts AC. knocking this down to the +/- 15 volt rails isn't an issue, but the infamous lm7805 can go into thermal limit as reducing 22 volts to just 5 wastes the rest as dissipated heat. This new design uses a switcher with well designed filter circuitry; the supply is very clean, very efficient (heat sink barely gets luke warm when before was too hot to touch), and the way its designed, even if the switcher fails, the linear regulator will always be in series to prevent damage to any digital logic. This supply's current rating gives the synths power hungry ttl logic more head room at 3 amps. The analog +/- 15 volt supplies are still linear, so no need to worry about any interference introduced into the signal path.

This new supply uses the existing transformer, and screws firmly to the bottom of the chassis on standoffs, as the original supply was mounted with crappy clamps suspended from the side of the chassis, and was notorious for falling off and causing internal damage. Currently the design requires the wires to be desoldered and resoldered to the board, but we could always toy around with the idea of using terminal blocks with those who don't feel comfortable soldering.

My synth has been extremely stable and functional for over a year now, and with the amount of passion I have for this instrument, I would love to help keep as many alive as possible. This is the prophet's Achilles heel, and having a modern and stable power supply will lead to many more decades of reliable operation. Any technical questions feel free to ask.



The supply can be seen here, I will try to take better pictures soon: https://youtu.be/Ahi6ST433uo?t=11

herdononge
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Prophet 5 Rev 3 Replacement Power Supply

Post by herdononge » Mon Dec 23, 2019 10:17 am

Im thinking of getting a new power supply for my Game Gear. Does it have to be Sega? Of course theyd say so on the back on the console...
But I was wondering what others use for the Game Gear? As mine doesnt have a power supply.

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