Parts layout for MN3207 Zombie wanted

[Mark Hammer]

I have a layout for an MN3207-based Zombie Chorus that someone posted, and I have a schematic.  What I'm missing is where to put the components that the layout provides for.  Can someone point me to one?  Thanks in advance.

[bean]

Looks a lot like this but reversed?

http://effectslayouts.blogspot.com/2017/07/zombie-chorus.html

[Mark Hammer]

I don't know who drew it, but I'd had trouble with another chorus layout from there that was drawn for an MN3007.  Turned out the modding it to work with a 3207 was going to be more complicated and uncertain.  This layout purports to be for a 3207, and it may well be just that.  The detective work to figure out where things ought to go just isn't worth my time, though.  If I have a parts overlay, I may etch and stuff it, but not unless I know I can end up with a working circuit.  Otherwise, it would just be easier to perf one using the schematic.

[Marcos - Munky]

I checked the link posted by Bean and took a look at the comments. One person posted a MN3207 version, but the link was broke. They said it was also posted here, so I did a search and found this one:
https://www.diystompboxes.com/smfforum/index.php?topic=123867.msg1175983#msg1175983

[Mark Hammer]

Hah!  That's the one.  Thanks a million Marcos.  VERY much appreciated. 

[Marcos - Munky]

Glad to help. Hope it sounds good, the Zombie is a very nice chorus and what makes it hard to build is the MN3007. If it sounds good with the easier to get MN3207, it'll be good news for people looking for a bbd chorus.

[RickL]

What am I missing? The layout using the 3007 sends +9V to pin 1 of the 3007 (ground) and ground to pins 4 and 5 (Vgg and Vdd). This gives the required (relative) negative Vdd/Vgg to the 3007.

If you reverse +9v and ground for the 3207 circuit you get the required positive Vdd/Vgg but it also reverses the voltages on the 4558 and 4016. How do the 4558 and 4016 work with a negative power supply?

[bean]

What am I missing? The layout using the 3007 sends +9V to pin 1 of the 3007 (ground) and ground to pins 4 and 5 (Vgg and Vdd). This gives the required (relative) negative Vdd/Vgg to the 3007.

If you reverse +9v and ground for the 3207 circuit you get the required positive Vdd/Vgg but it also reverses the voltages on the 4558 and 4016. How do the 4558 and 4016 work with a negative power supply?

- The voltage pin reverse is only for the MN3207 (which is N-channel instead of P-channel internally). You don't need to reverse voltage on anything else. You just have to remember that MN3207 is opposite in its polarity from MN3007 in a negative ground circuit.
- Couple other points - output mixing in MN3007 is usually done in conjunction with a pullup resistor whereas with MN3207 it should be pulldown (IOW supply vs. gnd).
- VGG with MN3207 is calculated as 14/15 the supply voltage.
- With MN3007, VGG is the inverse: Vgg= 1-V(14/15), where V is your supply voltage. Correction, I meant to say V-V(14/15) which is V(0.067). Hopefully I got that right this time.
- Same goes for MN3005/MN3205

Caveat - this is what I remember off the top of my head but I still get confused with these even after using them both for more than a decade. If I'm wrong I'm sure someone else can correct.

[RickL]

That's what I don't understand. If I'm reading the link correctly, it says that the layout will work for  a 3207 by simply reversing the voltages (plus the minor corrections needed for both versions - 10k to 10n and added 100k) on the board. That won't just reverse the voltages on the delay chip, it will reverse them on the 4558 and the 4016.

Did I miss a link on that page that changes the layout so the voltages are only reversed on the delay chip?

[Mark Hammer]

Hi Rick.

And just to clarify, that should read 4046, not 4016. 

[deadastronaut]

just my 2p...

i had distortion when using humbuckers with the zombie and just couldnt get rid of it no matter what i did, (tested at nauseam on breadboard)...if you whack a chord it would never be clean.....gave up and went a different route.

its ok if you use single coils though...(which i dont) 

as you were....

[Lordrahulcool]

@mark hammer

Did it work?

Is that pic already reversed?

[chovi]

Hi, could  someone share pcb transfer image in real size based on 3207 pls?

[Mark Hammer]

Images on that site are generally at actual size.  Right-click on it and select "open image in new tab".  When it opens, click enlarge "+", and that should provide a properly scaled image.

I generally clip the toner-transfer image and paste it into a new blank image to print multiple copies.  I print that out on regular paper, and directly compare it to the spacing of chip pins or a piece of perfboard or veroboard, adjusting the size of the image to get it right.  Some images on that site will include board measurements, which is helpful.

[percyhornickel]

I`ve build the 3207 version and works very good. I made some changes over that board trying to isolate feeding lines and grounds for the lfo, audio, bbd and 4046 sections. After all the mods there was always the small and tiny thick when the circuit was bypassed.

I could note the thick dissapears when a buffer pedal was in front so I build an small buffer and put between the input jack and the switch input pin, now I have a buffered 3207 zombie chrorus, works very very good and there is not weird noises.

For the hamb distortion issues I used LF353P instead 4558 for the audio section (as I did with the orange squeezer with 2N5458), that worked really well.

This buffer fits great below the 3pdt switch:
https://effectslayouts.blogspot.com/2015/05/simple-jfet-buffer.html

Saludos desde Venezuela

Percy

[percyhornickel]

I just wanted to write an update since I could note a big pop everytime I engaged the my ZC. The reason was the buffer I installed before so I had to put it out and then the small LFO click was there, I tried some fixes that helped a lot and now is working great. I have no distortion and I get a nice dead silence when I bypass the circuit. I use four +9V lines to feed every section of the circuit.

What I did:

AUDIO
TL062 (no distortion with hambuckers)
LINE 01: 9V - 33 Ohm - 100U

LFO
RC4558P
LINE 02: 9v - 33 Ohm - 100U
PIN 2 (INV INPUT): 4.5V (10K + 10K RES. DIV)

BDD
MN3207 / BL3207
LINE 03: VGG:8,36V (With a 10K trim + 3.3U and direct from 9V) VDD: 9V

CLOCK
CD4046
LINE 04: 9V - 100 Ohm - pins 14/15/16


JACKS
I have used aluminum tape between two pieces of transpart tape to cover/shield both jacks (even solder points), I could note the lfo click everytime the input and output jacks were exposed, once they were cover, as I said...   ...dead silence).

Use as short as posible cables for the jacks, shielded too.

LESLIE MOD
Do not use ceramic cap for 390p, try to use film type. In my build I used ceramics at first and the tick was present, once I changed for film the thick were reduce a lot. I used 330p cause that's what I have in hand.

SWITCH
One big reason why the ticks appears is the use of mechanical switch, the nine solder points is like a jar with "every signal comming in and out concentrated", I put a cable touching the switch chasis (using a couple of nuts) soldered right to the output ground...   ...big big difference!!!!


I have modified this nice layout from matlevo12 to make it work with the changes I wrote above:



My board now looks like a mess but works like a charm!!



I hope this could help to someone over here

Saludos