Tyco Pedalflanger

[armdnrdy]

I've been working with the schematic that Dirk Hendricks reverse engineered from an original Tycobrahe Pedal Flanger, a very bad schematic that's floating around, and the board shots of the reissue from the other site.

I came up with this:



Having never built a positive ground fuzz face, I didn't know what to think of this circuit's power arrangement upon initial review.
I moved past that learning curve and stumbled into another one....head first! The BBD section.

The original pedalflanger used two quad TL044's for the op amps and a MN3001 for the BBD. The 4046 fed one line to the 4069 which used two sections to buffer, and three sections to buffer and invert one of the clock lines. The sixth 4069 inverter was used in conjunction with other components to create a switching power supply to feed the MN3001's VBB. (pin 1)

The reissue turned out to be quite different in several aspects. After tracing the circuit, this is how I see it.
There are four TL022's for the op amps. The components that set the 4046 frequency were altered to drastically increase the frequency. The 4046 now feeds two clock lines to the 4069 who's sole purpose is now that of a dual buffer, using three parallel inverters for each clock line.

The BBD is now an eight pin model which is fed 0V to the VDD pin and -7.3V to the ground pin. Basically moving the whole power scale down from the traditional +V and 0V.
The voltage divider that feeds pin 4 (VGG) calculates out to -478.9mv.
The MN32XX data sheet specs VGG to be 14/15 of VDD. If VDD in this case is 0 volts then that calculates out to -486mv, right in the ballpark of our voltage divider.

So....because of the BBD having 8 pins, the 4046's increased frequency, and the BBD's power configuration, I'm 99.9% positive that the reissue's BBD is a MN3207. ( I forgot to mention that all of the ICs are painted over.)

Did you notice that I left that .1% of gray area? That's where you come in! What are your thoughts? Am I completely missing something?

There's one other thing.
The later reissues have a switch to shut off the gate. I can see clearly on the board image where it connects to, but the switch connection isn't very clear.
To switch off an N channel JFET you apply negative voltage to the gate. So common sense tells me that the P channel JFET in the gate section should be switched of when positive voltage is applied to the gate? Positive voltage in this case being ground.

Thoughts?

Here is Dirk's schematic of an original 70'S Flangerpedal.

[armdnrdy]

For those of you who aren't familiar with this flanger, this is some of what this thing can do:

There is a switch at the toe position for effect In/Out. When the effect is engaged you can control the speed of the auto sweep with the pedal.

There is another switch at the heel position. You can switch the pedal from the speed control/auto sweep to pedal sweep allowing you to sweep the frequency manually, custom tailored for musical passages.

[Mark Hammer]

Hmmm....maybe its time to adapt the old Anderton Pedal Flanger to a 3207?  http://hammer.ampage.org/files/Anderflange1.PDF

[armdnrdy]

Mark,
Do you think that my conclusion is correct?

I have never seen a MN32XX fed with negative voltage in this way.
I guess the IC doesn't know the difference between negative voltage and zero voltage, and the VDD pin is more positive than the GND pin.

[Mark Hammer]

First, I once again salute your diligence in chasing down something from beginning to end.  I wish I had your focus.

Second, for me the choice of chip would boil down to what the maker's expectations are for production.  The number of available MN3007s in the world is dwindling, but Coolaudio 3207s are readily available.  If someone was intending to make a run of 100, I suspectthey could likely find a stash here or there of 3007s.  If their plan was to make it an ongoing thing, then they'd be fools to base it around a 3007 rather than a 3207.

[wookie]

Is there a need for more info on this pedal?  I happen to have one back at the house.  I can gladly supply gut shots.  The only caveat - it's supposedly not working, and had a poor repair done to a regulator at some point, according to the guy who gave it to me.  I still haven't cracked this one open to check it out yet.  One of the many projects I've back-burner'd for too long.  I've got to fire it up, get some voltages written down and figure out how far off or nominal this thing is some time soon.  My main concern is that if the regulator went, it's because something down stream was shorted, and in the process of failing it may have taken some of those expensive BBD's along with it.

[armdnrdy]

Is there a need for more info on this pedal?  I happen to have one back at the house.  I can gladly supply gut shots.  The only caveat - it's supposedly not working, and had a poor repair done to a regulator at some point, according to the guy who gave it to me.  I still haven't cracked this one open to check it out yet.  One of the many projects I've back-burner'd for too long.  I've got to fire it up, get some voltages written down and figure out how far off or nominal this thing is some time soon.  My main concern is that if the regulator went, it's because something down stream was shorted, and in the process of failing it may have taken some of those expensive BBD's along with it.

Wookie,

Do you have a reissue or an original model?

Thanks for the offer! and yes....I can never get enough information or gut shots!

But I am in need of something else as well.....and it doesn't need to be from a working unit.
Readings of the dual pedal pot.

I'll PM you with details.

I learned quite a bit about this circuit so maybe I can help you fix yours. That would be a good trade for your help.

[Govmnt_Lacky]

Is there a need for more info on this pedal?  I happen to have one back at the house.  I can gladly supply gut shots.  The only caveat - it's supposedly not working, and had a poor repair done to a regulator at some point, according to the guy who gave it to me.  I still haven't cracked this one open to check it out yet.  One of the many projects I've back-burner'd for too long.  I've got to fire it up, get some voltages written down and figure out how far off or nominal this thing is some time soon.  My main concern is that if the regulator went, it's because something down stream was shorted, and in the process of failing it may have taken some of those expensive BBD's along with it.

Looks like a match made in heaven or a "you scratch my back... I scratch yours" kinda thing!  

Not only can YOU provide some needed gut shots of the real deal ..... you can also receive debug help to get your original pedal fixed!

POST 'EM UP BRO!!  

EDIT: Dang it Larry... beat me by 34 seconds!    

[armdnrdy]

I love this site! 

[armdnrdy]

EDIT: Dang it Larry... beat me by 34 seconds!    

Greg,
You do realize that there is a "pecking" order around here...right? 

[Govmnt_Lacky]

Greg,
You do realize that there is a "pecking" order around here...right? 

Guess Im low man on the totem pole huh?   

[armdnrdy]

Greg,
You do realize that there is a "pecking" order around here...right? 

Guess Im low man on the totem pole huh?   

You've been a member way before me....right around the time that Rob (deadastronaut) started that reverb pedal thread. 

[wookie]

It's an original!  The owner was going to trade it for a newer Boss DS-1 until I showed him how much the re-issues were going for.  Original owner used to have a TV/VCR repair business, and he never made progress on this thing, so I'm not sure how toasted it is.  He eventually tossed it my way to see if I could work on it when I had the time.  That was like two years ago and I've since left the company.  I'd love to be able to get it working just to play around with the dang thing for a week or two before I get it back to him.  Wouldn't that be a hell of Christmas gift!

Christmas 2014 likely...

Anyways, regarding the screen shots, I'll get something out soon.  I'm heading to a cabin in the woods for the thanksgiving week starting Sunday, so any follow up shots will be a little delayed.

[armdnrdy]

Cool...thank you!

I'll PM a labeled picture of the pedal pot (so we're on the same page) and instructions on what measurements I need.

This is very helpful!!

[digi2t]

Greg,
You do realize that there is a "pecking" order around here...right? 

Guess Im low man on the totem pole huh?   

HAH!! When someone at work asks me what's going on, I tell them, "I'm so low on the totem pole, I'm the part that's buried in the ground". 

[bean]

I don't see any reason you can't just convert the entire circuit to negative ground. AFAIK there's no advantage here, but maybe someone can explain. You will need to re-do the VGG supply but that's easy enough. Or, if you want to play around, try the v3102 clock to reduce the footprint. You get VGG automatically from that (I think it is pin7). I don't know if you will need the CP buffers or not in that case.

[slacker]

I think you're right, Tycobrahe just seemed to like positive ground, the Parapedal is positive ground as well for no obvious good reason http://geofex.com/FX_images/parapedal.gif

[armdnrdy]

I've been toying with the idea of changing the pedals supply so that it will play nice with other pedals on the same power supply.

The 3102 wouldn't be able to clock the BBD high enough to emulate the original MN3001 used in parallel multiplex configuration.

As stated above, the reissue VCO components were changed to achieve a much higher frequency, double clocking the 3207.

[Mark Hammer]

The 3102 on its own might not be able to do the job, but maybe an assisted one could.  Remember, the whole point of buffering the clock lines is to provide enough current to overcome the input capacitance on the clock pins of the BBD.  Maybe the 3102 can clock high enough but simply can't deliver the needed current on its own.

[armdnrdy]

I pulled this initial board together based on one of the later reissues.

Still a lot to do!