TC electronics XII phaser

[Bassmanfox]

Hey,
My friend let me take a look at his broken TC electronics XII programmable phaser, the original NOT the reissue, for some reason the LFO doesn't always turn on, it filters and passes signal thru it, but it won't turn on the LFO sometimes.  Intermittent problems are the worst and it was stressing me out, so I figured maybe it'll be fun to reverse engineer this thing, turns out it really isn't that fun and this darn thing is a bit more complex then it first looked, I was just wondering if anybody has any info on this or would be interested in working on a project for it.  I have a hand drawn schematic right now, but I am slowly making one in ExpressSCH. 

[MartyMart]

I have the schem in two parts, PM me an email address and I'll forward them to you.
It's a complex beast indeed !!
I have the "BK" version voiced for bass/keyboards and it does sound superb
Marty.

[Mark Hammer]

If I'm not mistaken, the original used the legendary SSM2040 filter chip (really just a quad OTA chip optimized for filters).  Those chips are long since out of production and VERY hard to find.  Because SCI Prophet Five owners need 5 of them to keep their beloved synths alive, the going price for them, IF you can find them, is around $50@.

So be very very careful.  Here's an example of the 2040 in action:

[Bassmanfox]

I see no chip labeled like that, but there is one that has the top sanded, but it has to be a quad amp because its the in and out point and its set up just like one.  There is a CD4007, a Lm339, a cd4011, and 2 chips which I believe are part of the filtering/LFO section they have the label 4741CP on top, which I THINK means they are MC4741's, found here http://www.datasheet.in/datasheet-html/4/7/4/4741CP_ETC.pdf.html.

If anyone has any other suggestions as to what the 4741CP would be I'd like to know.  Hopefully I'll post some pics soon.

Ohh yeah and all of the chips on board are 14 pin chips, so they can't be the 16 pin SSM2040, phew.

Also this pedal is NOTHING like the tc electronics bass/keyboard phaser, that is if what marty sent me is correct, which it looks to be.  So if anyone has any more info that would be great, otherwise I'll keep you all posted.

[Mark Hammer]

Interesting, and somewhat of a surprise based on what I'd heard.  Thanks for the correction.

Are there FETs on board or is the 4007 being used as the variable resistance to ground?

[MartyMart]

Brian, I'm pretty sure that the one I sent is the "standard" guitar version, not the "B/K" version, I just
happen to own one of those B/K phasers.
is it not matching up with what you have ??
MM

[Bassmanfox]

marty, yeah it really doesn't look like what you sent me and what I have are the same thing.  Heres the INCOMPLETE schematic as I have it now, tell me what you think.  Note: Nothing has been double checked yet and I need to stop for a bit because I am going cross-eyed.

The ? IC is what i think is a quad op amp. 

[Mark Hammer]

I applaud your diligence.

You will pardon my impudence.  Just one question:  Where exactly is the phase-shift taking place?  Or has everything that B1/C1 connects to been left out?

[Bassmanfox]

Yeah that whole section is left out right now as I said I was going a little cross eyed

[Bassmanfox]

Just want to let you all know I got a somewhat verified schematic of the Phaser completed.  I say somewhat because I have only double checked it and I really need to triple check it and then actually lay it out and try it.  I was hoping there was someone else out there who also has one of these phasers and wouldn't mind helping out.  Its a bit of a beast I know, buts its really got a sound unlike other phasers with the function knob and filter switch there is really a different world of phasing each time you adjust these parameters.

Also anyone kind enough to maybe describe whats going on with all these parts would be in my debt. I'd really like to know what the CD4007 does.  Also there is an unlabeled input to the phaser that I have labeled on the schematic as 1/8" IN.  Would that be a CV In do you think?

Also I was hoping that you guys could maybe comment a little on the layout of the schematic and give any pointers. 

Thanks ahead of time. 

[gez]

I'd really like to know what the CD4007 does. 

I don't have data sheets to hand, but the 4007 is almost certainly being used for switching duties.  By the look of things, it switches in the wet signal to be mixed with the dry; the latter being always on ('bypass').

At a glance, it seems that the top right hand corner is the LFO.  Reflow some joints in that area?  I'm afraid I don't have the time to go through the schematic in any detail.  Good luck with it!

[lowstar]

congrats on the effort to do the schemo. i have guests for dinner tonight and so will check later this weekend.
but a quick stab before i start cooking: in many of the old tc pedals, an 1/8" jack is used for remote switching (so you can have your pedals in a rack drawer near the amp).

cheers,
lowstar

[matlevo12]

Hi !

By any whance, did you manage to find out what was wrong with your phaser ?
I have one that seem to stay "dry", meaning that the function pot and the filter switch have some effect on the sound but nothing comes from the LFO (speed and width pots don't do a thing and the signal isn't influenced by any phase-shifting).
I replaced the LM339 chip but it does'nt solve anything.

Maybe the CD4007 is dead and doesn't mix the signals ?
I looked very carefully and see no visual signs of damage or bad solders.

If anyone has an idea I'm all ears !

Thanks !

[Kevin Mitchell]

Hi !

By any whance, did you manage to find out what was wrong with your phaser ?

You likely wont get much help trying to reanimate a 12 year old topic. Try starting a new thread. Record some voltages as well.

-KM

[Mark Hammer]

I'm not seeing enough "stuff" in that drawing to support 12 stages, as the device claims.

[Scruffie]

I'm not seeing enough "stuff" in that drawing to support 12 stages, as the device claims.

I'm severely struggling to read that schematic (I don't think whisky is helping either) but those might be second order all pass filters?

[anotherjim]

Does it fake a double-length by reversing the polarity to give the illusion of shifting up to and beyond 180 degrees?

[matlevo12]

Hi !

By any whance, did you manage to find out what was wrong with your phaser ?

You likely wont get much help trying to reanimate a 12 year old topic. Try starting a new thread. Record some voltages as well.

-KM

Thanks for the tip, you're right.
I'll try and do that when I have the time to do it properly. The schem might not be 100% accurate according to what I tested, or my pedal is really messed up.

[Fender3D]

I posted the complete service manual on the other site...

[matlevo12]

I posted the complete service manual on the other site...

Hi !
Thanks for the info, found it !
I'll try and see if I can manage to shed light on my problem with this !