What are the common problems with the SCI Prophet 600?

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What are the common problems with the SCI Prophet 600?

Postby tyrannosaurus mark » Mon Feb 08, 2010 5:56 pm

I've been offered a second hand Sequential Circuits P-600, and I'm wondering what the common problems with the synth are. Here's a list from my searching on VSE and it's fairly generic, anything to add?

-Dirty key contacts
-Dead voices
-Cut off knob steps the filter (from the factory, a problem with the operating system?)
-Broken touch pad buttons
-OS freaking out

I'm going to go check it out tomorrow so I just want to know what to look for. Maybe share your story? I'll be keeping my ear out for un-snappy filters!
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Re: What are the common problems with the SCI Prophet 600?

Postby CfNorENa » Mon Feb 08, 2010 7:42 pm

I would just add that the stepping on the filter isn't really a "problem" on a faulty unit, but a standard feature of the synth itself, even when working properly. But you've probably also read that the stepping is only audible (and it is VERY audible) when manually turning the cutoff knob; if you modulate the filter with anything else (e.g., LFO), it's as smooth as butter.
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Re: What are the common problems with the SCI Prophet 600?

Postby pricklyrobot » Mon Feb 08, 2010 7:54 pm

-Dirty key contacts
Yep, but pretty simple (if tedious) to remedy. Details are on the Old Crow page.
-Dead voices
Possible, but not Juno-106-type inevitable. And there are still a fair amount of CEM chips floating around (although the VCF chips seem to be easier to find than the VCO's).
-Cut off knob steps the filter (from the factory, a problem with the operating system?)
You're just dealing with the limitations of early '80s microprocessors here. But you can get perfectly smooth filter modulation via the LFO, or the Filter CV input (0-10V, so you can wire up a 9V battery to a volume pedal and have a nifty filter expression pedal) on the back.
-Broken touch pad buttons
I've had no problem with mine yet, and I've had it for 3 or 4 years now. Chipforbrains (aka Technology Transplant) on Ebay has newly-manufactured replacement membrane pads for sale for a reasonable price (around $45 US, I think) on a semi-regular basis. I picked one up as a back-up a while ago, but haven't needed it yet.
-OS freaking out
Haven't heard about this one, and fortunately no first-hand experience.

I love my P-600. Best $400 I ever spent, and I'd still dig it at twice the price. Fortunately, I've had no serious issues with mine, but they're easy to open up and seem like they'd be pretty straightforward to work on, provided you could get your hands on the necessary chips.
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Re: What are the common problems with the SCI Prophet 600?

Postby CfNorENa » Mon Feb 08, 2010 8:12 pm

pricklyrobot wrote:I love my P-600. Best $400 I ever spent, and I'd still dig it at twice the price.


I'll second that. Two weeks ago I traded a JX-10 + PG-800 + $200 for mine (so, a bit more than $400), but I've been very happy with it. Biggest and most pleasant surprise thus far is how "pretty" it can sound. Yes, with its Curtis chips it will definitely give you that trademark "sizzle" and "growl," but turn the resonance to zero and you get some absolutely beautiful tones.
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Re: What are the common problems with the SCI Prophet 600?

Postby otto » Mon Feb 08, 2010 8:19 pm

Yeah the steppy filters are just par for the course, it’s a pretty common “feature” of early synthesizers with processors, just perhaps a bit pronounced in the P600. So on one hand it’s not really the synth you’d get to twist the filter knobs while playing live, although the stepping can be used as an interesting sound effect in its self. Internal modulation of the filter doesn’t step. Also you can use a foot pedal to modulate the filter and that doesn’t step either.

I’m on my second P600 and it was rather maltreated. I’ve never had a problem with the touch-pad. I’ve never lost a chip either, I know it happens but it can happen in any vintage synth. We’re not talking Juno 106 issues.

One issue that comes up is that if your pots get too dirty you can have freezing issues. What is happening is that the processor scans all the controls for movement, grit in a pot make the pot appear to be in movement and the processor is trying to process that pot. Twist your pots back and forth a bit for some self lubing action or clean/lube them. I’ve never experienced this problem either but it’s know to happen. It’s more of a glitch than any kind of permanent issue.
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Re: What are the common problems with the SCI Prophet 600?

Postby otto » Mon Feb 08, 2010 8:29 pm

CfNorENa wrote:
pricklyrobot wrote:I love my P-600. Best $400 I ever spent, and I'd still dig it at twice the price.


I'll second that.


x3.

One of the best bargains out there, great sound that is characteristically "prophet" but has its own unique flavor. I know there is some polarization on this synth. It does seem to be a bit of a love or hate synth. Some people can’t get over the steppy filter (get a monosynth if that’s what you’re looking for, this isn't a poor mans Pro-One). IMHO it’s got a bit more aggressive and dark sound compared to a P5, in fact I’d dare say it actually sounds ballsier than a P5 to me but isn’t as easy to tame and smooth until you get to know it.
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Re: What are the common problems with the SCI Prophet 600?

Postby code green » Mon Feb 08, 2010 8:32 pm

+1 on everything prickly robot said, especially the bang-for-buck factor. as for the OS freaking out, on the two prophets i own there is a very occasional problem (which i know others have had, via this forum) in which the pots stop responding to changes--most likely because the processor gets hung up reading one pot as continually changing. some have dealt with this problem, when it's come up, by making slight adjustment to all the pots so as to find the one causing the problem and end the continuous scanning of that pot...others have found that moving the pitch or mod wheel soles it. me, i've generally i deal with this problem by turning it off and then on again. but again, it's rare that this crops up. i gigged continuously with my two different p600s for three years and had very few problems on stage (despite my at-times melodramatic posts on this subject)--and it's possible that none of them were actually attributable to the synth itself (i'll start blaming the synth when i have a consistent, dependable monitor mix throughout our entire set--until then, i'll reserve judgment).

then again, if i was playing huge venues with a name act i'd either play a more modern board or have backup/a dedicated synth tech. but i don't see the p600 as more trouble-prone than any other vintage synth, and good luck finding any other 2-vco poly for its price--never mind one that sounds this good. one other thing to add to the above--the stepping on the filter control is only very noticeable with high resonance. and with some practice even manual filter sweeps with high resonance can be made to sound pretty smooth.
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Re: What are the common problems with the SCI Prophet 600?

Postby pricklyrobot » Mon Feb 08, 2010 8:58 pm

Not to hijack, but as long as we've got all the P-600 people in one thread, I'm wondering about one relatively minor issue I've noticed with mine.

With the Poly-Mod section, when using Osc B to modulate the filter, every 4th note or so that I play comes through sounding noticeably less filtered. When Poly-Mod is off, all notes sound equally filtered, so I don't think it's a faulty VCF chip. Maybe something needs to be calibrated, or it's just a quirk of how the Poly-Mod works?

I think it's always done it and it just took me a while to notice. It hasn't annoyed me enough yet to put a whole lot of effort into finding an explanation, but I thought I'd ask as long as we're here already. ;)
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Re: What are the common problems with the SCI Prophet 600?

Postby code green » Mon Feb 08, 2010 9:35 pm

hey prickly--i'll check it out when i head up to the studio in a bit. i welcome the chance to get more acquainted with what to expect from the polymod section, as i really didn't hear it in all its glory until i got my second p600...my first must've needed some work as the changes it wrought were very subtle...but then again, i was a lot less experienced with programming in general when i was using that one. need to get the keypad on the first one replaced and do a thorough A/B, as i think i preferred the sound on the first (a bit less mellower/less biting). the first was a significantly earlier serial number and i remember seeing reference to various revs here, so perhaps that's the issue? anyone know of significant differences between the various p600 revs?

so now i've jacked your thread jack...think we should start an all things p600 thread to share all this kind of info along with programming tips, etc? and will let you know about the polymod/filter issue....
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Re: What are the common problems with the SCI Prophet 600?

Postby tyrannosaurus mark » Mon Feb 08, 2010 10:12 pm

Thanks for all the info guys, very very helpful!

Seeing as this has been moved to the buyers thread, I'm actually going to be swapping my Moog Little Phatty SE for the Prophet 600. I can't really decide properly until I can play the thing tomorrow as to whether to go ahead with the trade or not. Wish me luck! :) And keep the info coming if there's any more.
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Re: What are the common problems with the SCI Prophet 600?

Postby carbon111 » Mon Feb 08, 2010 10:56 pm

pricklyrobot wrote:
-Dirty key contacts
Yep, but pretty simple (if tedious) to remedy. Details are on the Old Crow page.


Did this fix for my P600 and it was only partly successful, I still had intermittant keys.

The solution was to get the Circuitworks Rubber Keypad Repair Kit, available from many electronics supply.

Image

Best seventeen bucks I've ever spent! The keyboard works flawlessly now. :ugeek:

In my opinion, the only real shortcomings of the P600 is the rather coarse knob quantization, too-fast LFO and the slightly sluggish envelopes.
Overall, the basic sound of the beast is both bold and lovely. I love the non-linear filthy filter rez of the CEM3372!

...I do have a spare keypad just in case. ;)

I love my Prophet 600! :yahoo:
Last edited by carbon111 on Mon Feb 08, 2010 11:06 pm, edited 3 times in total.
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Re: What are the common problems with the SCI Prophet 600?

Postby calyx93 » Mon Feb 08, 2010 11:01 pm

Mushy attacks on envelope modulated filtered patches are another symptom/feature of the heavy load on the P600's CPU - however, it can make some crisp attacks if you have the settings right. It'll still take some experimentation, but it can be done - just not as flexibly or throughout the entire parameter ranges as a P5/Pro-One.

In the VCF section, I've found that keeping the envelope mod amount in the higher numbers - 7-10, keeping the cutoff higher and using a very, very short decay and medium-to-low sustain settings will allow for some tight basses, jabs and pinprick zaps (even mallet-y sounds - sort of). Settings that work well on the P5 just don't sound the same on the 600 - but the beefy bass response of the 600's filter is really something else, and seems to make up for the envelopes.

BTW - cleaning the key contacts is much easier than it seems - did mine (first time, mind you) within 30 min. Helped the feel and responsiveness immensely - I highly recommend doing it.
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Re: What are the common problems with the SCI Prophet 600?

Postby tyrannosaurus mark » Mon Feb 08, 2010 11:47 pm

Looking through all the demos online of P-600s, it seems that people who like demoing P-600s LOVE long decay sounds, with lots of slow filter movement. Sounds like a Vangelis score or something!

Guess I'll have to find out tomorrow if I can get my bleeps and bloops like I like em :)
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Re: What are the common problems with the SCI Prophet 600?

Postby otto » Tue Feb 09, 2010 12:01 am

Not a very bloopy/bleepy synth IMO, the envelopes aren't real fast. Not that it can't do some of that but there are many other synths better suited for that including the one you have... I think it's strengths are thick pads, strings and haunting dark sounds. I think the LP is a great synth as well but they are too different to try to compare, just depends on what you're after...
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Re: What are the common problems with the SCI Prophet 600?

Postby code green » Tue Feb 09, 2010 2:40 am

given the ca. $1000+ going price for the little phatty, that doesn't seem like a great trade--unless prophet 600s have really gone up in price lately.

not speaking to the relative merits of the two synths here--just the rough dollar values...
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