Please be aware that information is provided for help only and not binding. As I get quite a few emails now, I can't guarantee I will be able to respond every time but hopefully this page will help others to get to grips with troubleshooting this fabulous synth. I'm not an expert on these synths, so for detailed troubleshooting, check out the Prophet 5/analogue synth forums. Contact me for any corrections or improvements also. If in doubt about a repair, always take the synth to a reputable synth technician.
In 1978, a few guys in a garage in San Jose, California who called themselves Sequential Circuits created the Prophet 5, a synthesizer with five voices of polyphony and enough memory to save 40 sounds. This may seem like nothing today, but back then it was pretty impressive. But what really set the Prophet apart from it's contemporaries was it's sound, a sound that is now legendary.
Synth players fell in love with the Prophet when it hit the streets, pushing Sequential into one of the largest American synth manufacturers by the late 80s. Soft Cell, Devo, Gary Numan (who had five!), OMD, Frontline Assembly, INXS, Kraftwerk, PIL, and the Talking Heads, among others, all rocked the Prophet.
If you're looking for a Prophet 5 nowadays, expect to pay around £2500++ for a non midi'd one in good working order. Also, keep in mind that there were several different versions (or revs) of the Prophet released in it's lifetime. The early revisions are very expensive.
The Prophet 5 contains five individual voices. For it's principal sound sources each voice contains two VCO's (voltage controlled oscillators), OSC A and OSC B, and a white noise source which can be mixed into a resonant low-pass VCF (voltage controlled filter). The filter modifies the voice timbre under control of it's four-stage envelope generator. The filter may also be resonated and serve as a sound source. Following each filter, a VCA (voltage controlled amplifier), also controlled by a four-stage envelope generator, shapes the voice amplitude. Supplementing the basic voices are polyphonic modulation (POLY-MOD) signal routings within each voice that allow OSC B and the filter envelope generator to function as modulation sources applied to OSC A frequency or pulse width, or the filter frequency. Finally, there is a single LFO (low-frequency oscillator) and a pink noise source which can be mixed to modulate all five voices, as adjusted by the MOD wheel.
Here's a screen grab I did of the OS EPROM in 2017
Instrument serial numbers are coded by model number, followed by a full stop and then the rev level. Mine is a Rev 3.3.
1000.1 -- Rev 1: Serial Numbers 1-182
Below are a few random pictures of DAC's etc.