Early Sequential Circuits Pro-One power supplies

xpander · Post by **xpander** » Fri Nov 02, 2007 9:54 pm

i'm on the verge of buying a near-mint Pro One this weekend... i checked it out yesterday... the contacts need cleaning but otherwise it was solid.

after i left it, i realized it had an early serial number (in the 800's i think) which i understand makes it the version with the power supply mounted to the main board, making it more delicate and making the board much more prone to cracking and other fatal damage.

so i call on the wisdom of Pro One owners: how concerned should i be? should i open it up before i buy it? i think i read of power supply/transformer changes that can be made to move it off the main board- is this true?

thanks!

Rookwood · Post by **Rookwood** » Sat Nov 03, 2007 12:05 am

I've used mine nearly continuously since I bought it new, and the transformer/PS hasn't been an issue. This includes heavy gigging in the late 1980's.

By now, the regulators have darkened the circuit board (they aren't heat sinked like in most other applications), but nothing I'm worried about.

Yours should be fine (especially since it sounds like it's been well care for), unless you plan on strapping it around your neck and bouncing it against your body during performances!

But when you're in there cleaning the j-wires, check for and fix any cold solder joints on the transformer connections.

Rookwood · Post by **Rookwood** » Sun Nov 04, 2007 10:30 pm

I had to open my Pro-One today, so I thought I'd snap one of the transformer. You can see the screw just to the right of the transformer that attaches to the panel standoff, so the transformer is secured, but obviously a sharp drop or shock will cause stress to the circuit board.

Later revs moved the transformer to the chassis.

By the way, did you get this unit?

xpander · Post by **xpander** » Mon Nov 05, 2007 2:31 am

yep... your studio is not the only one in the bay area now with a Pro One, Xpander and Prophet VS!

i need to open up the keyboard and clean the keyboard contacts, that'll be a new experience. earlier today i replaced two pots on my Jupiter-6, and i'm hoping also to CV-mod my Prodigy, too... everything is getting ready to start recording again.

Post by **wiss** » Mon Nov 05, 2007 7:38 am

xpander wrote:so i call on the wisdom of Pro One owners: how concerned should i be? should i open it up before i buy it? i think i read of power supply/transformer changes that can be made to move it off the main board- is this true?

thanks!

the only real issue is that it will be prone to odd hum's. its an easy mod to move the power supply off the board.

xpander · Post by **xpander** » Tue Nov 06, 2007 6:15 am

thankfully no hum, everything works great except the keyboard. cleaning the contacts really didn't help although it was clearly needed; i'll clean them once more before turning to plan b. any suggestions?

tomorrow i should have my Kenton Pro-2000 to interface it with, that should be fun!

Rookwood · Post by **Rookwood** » Tue Nov 06, 2007 6:33 am

xpander wrote:thankfully no hum, everything works great except the keyboard. cleaning the contacts really didn't help although it was clearly needed; i'll clean them once more before turning to plan b. any suggestions?

This usually means the gold plating has worn off, so a new wire-to-bar connection needs to happen. This can be accomplished by rotating the bus bars, and bending or pulling the j-wires back so that fresh gold-on-gold contacts are made. The bus bars are a hassle because they're soldered, but sometimes you can rotate them just enough to expose fresh metal without having to unsolder them.

Or you can replace J-wires, if it's only a few.

Some people like to use Cramolin or Pro Gold, but those things don't help if the plating is worn, pitted or corroded.

xpander wrote:tomorrow i should have my Kenton Pro-2000 to interface it with, that should be fun!

I have the Pro Solo - Kenton makes good stuff, and I don't clean my contacts much thanks to having the midi-to-CV!

xpander · Post by **xpander** » Tue Nov 06, 2007 7:33 am

i'm also going to have to address one of those clear yellow plastic flyswatter-looking widgets that stick to the end of the key and physically move the j-wire to the bar- one of those doesn't want to stay on its key. is there a recommended non-permanent goo to keep it attached to the key or should it just be replaced?

xpander · Post by **xpander** » Thu Nov 08, 2007 9:43 am

second cleaning worked, now it's back to normal (other than the yellow thing that will eventually go loose).

Early Sequential Circuits Pro-One power supplies

Early Sequential Circuits Pro-One power supplies

Re: Early Sequential Circuits Pro-One power supplies