In January 2019, I was contacted by a gentleman who happened to be the original owner of an early serial of a Revision 1 Prophet 5. This was of course very exciting to me, as he was considering letting it go for a fair price.

There’s nothing I love more than a fair deal for good gear. The transaction and “negotiation” couldn’t have been more friendly and above board. We settled on a number and a meeting place, and I then drove 4 hours north of Los Angeles to give the gentleman cash in exchange for Prophet 5 #14.

The idea of getting not just a Rev 1 Prophet 5, but #14 was surely frightening. I’ve worked on a small handful of Rev 1’s in my time, but never one this early. The others, ranging in serials from 110-180, all had nice PCB’s and were built like a production product. They were like working on kludgy Rev 2’s. Matter of fact, the other few Rev 1’s I’ve restored were modified to basically be Rev 2’s by other techs, with cassette storage and all.

The Prophet had a pretty cool story to go along with it too. You have to remember that in order to get a serial this early, you had to have either pre ordered or have waited for the store to open on release day. The former was true for this. He put a down payment on it before it was released with Don Weir’s music store in San Francisco. The Prophet almost ended up being ripped away from him, as apparently Carlos Santana was eager to get a Prophet 5 as soon as possible following release. The music store had tried to make an excuse as to why this Prophet 5 wasn’t ready for it’s rightful owner, and only after getting a bit nasty with them did the gentleman discover why; they had written Santana’s name on the box in big black letters, probably because he called in for it and they figured they could make the guy wait for another one. He did win the argument, and went home with his Prophet 5.

The guy was also in what must have been a pretty successful cover band as well (a Prophet was a very pretty penny in those days). Part of their thing was all of their instruments being blacked out. This was sort of unfortunate, as the badges had to be removed for the guy to properly black out the Prophet, but he did it in a way I now appreciate. He covered the unit in black contact paper. Then, when he stopped using it, he put it in an anvil case that ended up rotting out. The contact paper basically caused the beautiful Koa wood to be kept in time capsule condition. When I got it back to my shop, i carefully peeled back all the contact paper to find fresh, gorgeous Koa Wood.

Since I run an incredibly busy shop, I rarely have time to work on my own gear unless its something we can expect to be rented our frequently. This means a lot of my own projects sit on a shelf until “one day”.

In the time it waited for it’s day to shine on the bench, we brought it to the Synthplex convention near our shop along with a trove of other vintage goodness. Sequential happened to be right across the hall from us. Their employees got a kick out of seeing our Prophet 10, and of course the early Prophet 5. Dave Smith is not known for being keen to discuss his vintage gear, rather wanting to talk about his new Prophet 6, which is a fantastic piece of new gear of course. Dave was actually seemingly interested in seeing this Prophet, as he knew this was not only an early one, but early enough that he assembled it inside his garage.

We happened to have some Prophet 5 replacement badges at our shop. We got one and rubbed off the Prophet 5 logo with some acetone. We brought it to the convention the next day and were honored that Dave Smith agreed to sign it to adorn the Prophet 5 he built with his hands. That signature is now affixed to the front. The other usual badges will be affixed to their respective location as the restoration unfolds. Thanks Tony K for making that happen!

Finally in October 2019 I had a free day to finally start work on my Rev 1. The guy who sold it to me told me that he’d never ever had it serviced, so I was expecting it to be unaltered inside, which it was… luckily.

Due to the old tantalum capacitors in these, it’s not a good idea to power them until they’ve been replaced. I was a bit disheartened to know that the gentleman who sold it to me did try and power it before contacting me to see if it worked. I was happy to find that the fuse holder was broken, though, so most likely this hasn’t been powered since the days it was in use!

I started of course by replacing the fuse with a new fuse cap and fuse, then opened her up. Boy was it dusty in there!

The PSU as it was originally. The 2200uF cap on the supply is so obviously kludged in there. There are some small labels on the larger capacitors which look like they could be to specify which components the capacitor is filtering for.

Kludge on the bottom of the power supply. That diode actually ended up breaking in half and was replaced with the same part.
Blue tantalum capacitor here did not have its own holes on the board and was clearly added after board manufacturing. The yellow tantalum on the left is one of our replacement capacitors.
Blue trim pot here is to trim +15 to match -15 symmetrically.
Photo of my hand and the power transformer. Notice the red wire goes behind the PSU as this goes all the way across the synthesizer, under all of the backside I/O and eventually to a MOLEX connector that connects it to the front panel mounted power switch.
Following the previously mentioned red wires. These lead to the most telling feature of a Rev 1, the front panel mounted power switch. Notice on the right where the power cord comes into the chassis. Brown The green ground wire is quite kludged onto the grounding bus for all the I/O and then wrapped in electrical tape. The fuse holder is wrapped in tape as well, probably to prevent any freak accidents while in “service position”. Both AC lines go into the MOLEX. One for the switch filament, and one to be “switched” and then back through those red wires to the transformer. Notice the brown wire also is wrapped in electrical tape. If this was truly never touched by any tech in the time this gentlemen owned it, then it’s pretty clean how haphazardly these were made!
The red switch you can see the casing of is for record disable/enable. It’s a cool switch type you don’t see often anymore, whereas you must pull the shaft out towards you while actuating the switching action. This prevents accidental switching.
On other Rev 1 IC 10 is a 723 adjustable voltage regulator. I guess for this one (and probably others) they ran out… had a problem with it… or who knows… Instead, there is a flying 78L05 with two diodes connected to it. This powers the RAM while power is on. This regulator was dead on first power up, so was replaced with another 78L05.
Decent shot of the CPU board (more complete pics later following its recap of the tantalums!)
Few things of note here…
The way the battery is connected to the board, in my opinion, is incredibly funny. On the positive side, we have a large plated via with ground dangerously close by (notice the ring of flux). The battery tab goes through the hole and is soldered only to the inside of the large via, as it has a trace going under the battery. The negative side of the battery goes over a voltage rail on the bottom of the PCB, folds over the PCB, and then attached to a ground bus on the edge of the PCB on the opposite side.

The power supply connector is seen here on the right side under all of the polystyrene capacitors. It’s a MOLEX KK stye connector and pops in and out with relative ease. In a lot of ways, i prefer this to the later designs, but know that it’s definitely not superior.

78M08 is very much attached to this board! I love the small kynar wire for the in and out legs and that the ground is connected by a massive soldering to the ground plane. Boy do I hope that one never dies!

Closeup of the DAC and to the left you can see the area where the battery was after removal. There you can see the bit of plating that the positive side is soldered to.
I actually like the way they connected all the ins and outs. This DIP ribbon cable goes under the synth and to all the rear side I/O (except audio). Much easier to deal with (and probably a lot easier to break pins with!)
On the right, you see the voice board hovering above the CPU board. This isn’t significant for now, but what is is the screw thats visible.
One interesting thing inside Sequential gear is that they used flat oval head phillips screws to mount PCB’s to standoffs or the chassis. I always thought this was because the oval shape inevitably will “dig” itself into the PCB so slightly to create some pressure and prevent it from loosening during transport. However, after working on Rev 1’s, it also appears this was a necessity as some traces are planted way too close to mounting holes. If you look at the screw on the right, it’s clear that a normal button head screw would short out that trace. If the screw connects to the chassis, then it should work that trace to ground, thus potentially causing malfunctions.
Not pictured here, but many of those screws also go into threaded nylon standoffs, also because the rear side traces are planted too close to the mounting holes, and the nylon insulates it from creating shorts.
Casualties from removing the pot board for cleaning and recapping… The nuts on these pots were fastened extremely tight. I imagine this caused problems in the future. I’ve never had to muscle the nuts off like I had to on this Rev 1. Future Prophets seem to be just a little but more than finger tight.
Luckily, all that happened was the threaded collar detached from the base its crimped on by four little tabs. These were very much salvageable by realigning the tabs and getting them back on… this time just a little over finger tight 🙂

After a quick wipe down from years of grime. Restoration music choice also visible.
Closeup of the power switch. Notice the little bit of shielding from the jacket affixed to the panel.
Closeup of some kludgy goodness on the voice board. While it’s very haphazard that they’re glued on top of other IC’s, this is actually not too bad as they’re really just getting power off the chips below them. A wire from the CD4066 switch is fed into the + input of the op amp, while – and output are tied together with a wire going to a resistor. Clearly, those resistors have a similar footprint on the board thats being unused for the now buffer. Hopefully this demystifies this a little bit for those who think these early ones are really difficult to work with because of this feature (not saying they’re not!)
Here’s a pic of me trying to remove the keyboard so our awesome assistant Jolene could change the keyboard bushings. There is a flat heat screw where the greenie is, and a nut where the nut driver is. I actually don’t know what they did to secure this to begin with… but taking it out really seemed nearly impossible. The greenie here ended up sliding into the slot of the flat head screw to steady it while the nut driver removed the nut.
How did I take this picture? That’s being overweight for ya.

This is an unfinished blog entry that will be updated as time allows for the restoration to continue.