EM3207 (v1.1) - MN3207 based EHX Electric Mistress (9V) clone

[Govmnt_Lacky]

hi
it works right now, i need to adjust it but it works
the best sound at 15v, at 9v it is a little bit noisy.
Thank for your support

It is ALWAYS good to share the details of the repair so others can learn. 

[kowe90]

hi
it works right now, i need to adjust it but it works
the best sound at 15v, at 9v it is a little bit noisy.
Thank for your support

It is ALWAYS good to share the details of the repair so others can learn. 

Bad solder  and the pin 2 of the 1M pot is not connected in this layout, i see other schematic with this pin connected to the first pin

[armdnrdy]

Here is how you can improve the sweep ratio of the EM3207 Electric Mistress if it is poor (this is quite likely as I explain below !!!).

Here's the modification:   Replace R24 (30k) and R26 (10k) by a single 100k multi-turn (precision) trim-pot.
Pins 1 and 2 of the trim-pot should replace R24, and pins 2 and 3 should replace R26.
This effectively gives us the ability to trim the ratio of R24 to R26.

Question for DrAlx:

I'm working on a "version 5" build using an original R5106 that I came across.

I would like to implement your increased sweep mod, but I'm having a bit of trouble interpreting your description as to the placement of the 100K trimmer.

I worked on a drawing to replace the 30K and the 10K (version 5 = 11K) resistors with the 100K trimmer as described, (Pins 1 and 2 of the trim-pot should replace R24, and pins 2 and 3 should replace R26.) but this configuration makes a direct connection between the two op amp outputs with no resistance between them.

I worked up two other options...can you clue me in to the correct way to connect the trimmer?

Thanks....

LFO 1:


LFO 2:

[DrAlx]

Here is how you can improve the sweep ratio of the EM3207 Electric Mistress if it is poor (this is quite likely as I explain below !!!).

Here's the modification:   Replace R24 (30k) and R26 (10k) by a single 100k multi-turn (precision) trim-pot.
Pins 1 and 2 of the trim-pot should replace R24, and pins 2 and 3 should replace R26.
This effectively gives us the ability to trim the ratio of R24 to R26.

Question for DrAlx:

I'm working on a "version 5" build using an original R5106 that I came across.

I would like to implement your increased sweep mod, but I'm having a bit of trouble interpreting your description as to the placement of the 100K trimmer.

I worked on a drawing to replace the 30K and the 10K (version 5 = 11K) resistors with the 100K trimmer as described, (Pins 1 and 2 of the trim-pot should replace R24, and pins 2 and 3 should replace R26.) but this configuration makes a direct connection between the two op amp outputs with no resistance between them.

Looking at this schematic below from the Electric Mistress Mystery Page, the mod would involve removing the fixed 30k and the 11k resistors and using a 100k pot as follows.

The left pin of the pot goes to pin1 of the LM324.
The right pin of the pot goes to pin 8 of the LM324.
The middle pin of the pot goes to pin 3 of the LM324

Your first LFO pic is almost right (but the middle pin of the pot should go to pin 3 only).
One thing to point out is that I would use an internal trim-pot for this mod rather than a pot.
The reason being that if you try and generate too big a triangle wave, then the comparator part of the circuit that generates the clock will stop at the top of the sweep.
This will give an audible pop and then silence at the top part of the sweep (a "drop-out").

If I were going to expose this mod as an extra control pot on the front of the effects box (called "RATIO" or something),
then instead of connecting the left pin of this new RATIO pot directly to pin 1 of the LM324, I would make that connection through an extra resistor.  
That will stop the sweep from trying to go too high and causing a drop-out.
I couldn't tell you what resistor to use, and I would probably use an extra trim pot for it (adjustable from 0 to 100k say).
I'd set the trim pot at zero and gradually increase it until the SWEEP RATIO pot stopped giving "drop outs" at the top of the sweep.

[armdnrdy]

Thanks for taking the time to clarify and explain.

I just could not wrap my head around the proper connections!

I plan to use a trimmer (TR5) as you suggested in your original post about this mod.

Thanks again.

[digital-91]

Hi Tomas and guys in this thread.

I could build my EM3207 successfully.
I love this sound much !

Many informations and instructions in this thread helped me a lot.
I would like to say thank you all and report some photos of my build.

<photos>

I made PCB pattern for myself, because I wanted more thick PCB lines and some additional pads.
But, it is almost same as PDF's layout.


completed PCB.


I used 1590N1 case. It is a little bit bigger than 1590B size.


finished my EM3207. Both mode (flanger and filter matrix) works well.



<differences>

Basically, I followed PDF(v1.1) instruction, but I made some differences from PDF.

• D3 -> 10V/1W (couldn't obtain 10V/5W zener)
• RT3 -> 30K (couldn't obtain 22K trimpot)
• R18 -> 12k (for better wet/dry balance)
• C17 -> 47pF (clock cap. changed from 22pF)
• I added additional switch for changing clock cap value with using PAD CC(PAD 10 and 11).

<alignment>

I don't have an osiloscope, so I adjusted three trimpots like this.

• 1. Adjusting RT2(100k, BIAS) by a circuit tester.
  voltage pin3 of MN3207 should be 0.42 + 0.54*VCC (V)
• 2. Adjusting RT3(22k, CLOCK) by my ear.
  I believe I could get my best sound.
• 3. Adjusting RT1(10k, FEEDBACK) by my ear.
  I set the trim before oscillation when the COLOR pot MAX.

I'm not sure that I could tune it fine.
But I think I could get my best EM3207 sound.

Thanks  

[GodSaveMetal]

Hi Tomas and guys in this thread.

I could build my EM3207 successfully.
I love this sound much !

Many informations and instructions in this thread helped me a lot.
I would like to say thank you all and report some photos of my build.

<photos>

I made PCB pattern for myself, because I wanted more thick PCB lines and some additional pads.
But, it is almost same as PDF's layout.


completed PCB.


I used 1590N1 case. It is a little bit bigger than 1590B size.


finished my EM3207. Both mode (flanger and filter matrix) works well.



<differences>

Basically, I followed PDF(v1.1) instruction, but I made some differences from PDF.

• D3 -> 10V/1W (couldn't obtain 10V/5W zener)
• RT3 -> 30K (couldn't obtain 22K trimpot)
• R18 -> 12k (for better wet/dry balance)
• C17 -> 47pF (clock cap. changed from 22pF)
• I added additional switch for changing clock cap value with using PAD CC(PAD 10 and 11).

<alignment>

I don't have an osiloscope, so I adjusted three trimpots like this.

• 1. Adjusting RT2(100k, BIAS) by a circuit tester.
  voltage pin3 of MN3207 should be 0.42 + 0.54*VCC (V)
• 2. Adjusting RT3(22k, CLOCK) by my ear.
  I believe I could get my best sound.
• 3. Adjusting RT1(10k, FEEDBACK) by my ear.
  I set the trim before oscillation when the COLOR pot MAX.

I'm not sure that I could tune it fine.
But I think I could get my best EM3207 sound.

Thanks  

Please man post your LAY, PCB an connections, all you have, I love that pads!!!!! please man!!!

[digital-91]

Hi, Roberto.

OK, I'll share my PCB pattern here.

First of all, I create my PCB layout with referring to EM3207_v1.1_Build_Instructions.pdf.
Thanks Tomas.

PCB pattern file is here. em3207_pcb_pattern.xps. It is zipped.
https://anonfiles.com/file/5da23578c14c7fd217e1beb0c3effbaa

There are 12 short jumpers. see red lines.


I did it like this.


And parts layout is here.


There are 3 long jumpers. see red lines.


I did it like this.

• Positions of pads for SW_MODE are almost same as EM3207_v1.1_Build_Instructions.pdf.
  Please check PDF.
  
• Pads for pin1 and pin2 of 1M pot (RATE) are connected already.
  Because I could get reverse log pot.

I hope this help.
Thanks.

[GodSaveMetal]

Please man the lay or your PCB pattern not compatible!! would you post in other format or photo format or PDF?; thanks for your help!

[digital-91]

Hi,

If you are using windows pc, you can view .xps format without difficulties.
But, I transformed it to pdf format.

Follow this link to download.
http://www.filedropper.com/em3207pcbpattern

Click "Download This File", file name is em3207_pcb_pattern.zip.
This zip file contains .xps and .pdf both.

[GodSaveMetal]

Great!!!!! THANKS man I see the PATTERN in PDF archive.

[armdnrdy]

Hi,

If you are using windows pc, you can view .xps format without difficulties.
But, I transformed it to pdf format.

Follow this link to download.
http://www.filedropper.com/em3207pcbpattern

Click "Download This File", file name is em3207_pcb_pattern.zip.
This zip file contains .xps and .pdf both.

Comes up as broken link.

[digital-91]

>Comes up as broken link.

Now, I checked the link, though, it was still alive.
Can't you see that link ?

[armdnrdy]

Follow this link to download.
http://www.filedropper.com/em3207pcbpattern

Yes I can see it...but when I click on the link it takes me to a broken link page.

[digital-91]

>Yes I can see it...but when I click on the link it takes me to a broken link page.

I uploaded again, em3207_pcb_plus_a.zip.
https://anonfiles.com/file/39522015fb69bdb7a7457d8ab045cf71

[GodSaveMetal]

<differences>

Basically, I followed PDF(v1.1) instruction, but I made some differences from PDF.

• D3 -> 10V/1W (couldn't obtain 10V/5W zener)
• RT3 -> 30K (couldn't obtain 22K trimpot)
• R18 -> 12k (for better wet/dry balance)
• C17 -> 47pF (clock cap. changed from 22pF)
• I added additional switch for changing clock cap value with using PAD CC(PAD 10 and 11).

<alignment>

I don't have an osiloscope, so I adjusted three trimpots like this.

• 1. Adjusting RT2(100k, BIAS) by a circuit tester.
  voltage pin3 of MN3207 should be 0.42 + 0.54*VCC (V)
• 2. Adjusting RT3(22k, CLOCK) by my ear.
  I believe I could get my best sound.
• 3. Adjusting RT1(10k, FEEDBACK) by my ear.
  I set the trim before oscillation when the COLOR pot MAX.

I'm not sure that I could tune it fine.
But I think I could get my best EM3207 sound.

Thanks  

You say that C17 have to change to a value of 47pF, and add a toggle switch to change that values; what values you use? and how you connected it to the pads 10 and 11?

Thanks man!!!

[digital-91]

Hi,

You say that C17 have to change to a value of 47pF, and add a toggle switch to change that values; what values you use? and how you connected it to the pads 10 and 11?

Thanks man!!!

See this photo, first.


I changed C17 from 22pF to 47pF because I read this comment.
http://www.diystompboxes.com/smfforum/index.php?topic=91981.msg896276#msg896276

And I'm using a SPDT (on-off-on) switch and 22pF and 47pF capacitors, and

• connect SPDT switch pin 1 and 47pF pin 1.
• connect SPDT switch pin 3 and 22pF pin 1.
• connect SPDT switch pin 2 (center one) and PAD11. blue line in photo above.
• connect 22pF pin2 and 47pF pin2 and PAD10(= GND). black line in photo above.

This additional SPDT switch and 2 caps mod is optional,
EM3207 works fine without this mod, you know.

I hope you enjoy this.

[GodSaveMetal]

Great digital-91, thanks man !!!!!!!!!!!!!!!!!!

[armdnrdy]

>Yes I can see it...but when I click on the link it takes me to a broken link page.

I uploaded again, em3207_pcb_plus_a.zip.
https://anonfiles.com/file/39522015fb69bdb7a7457d8ab045cf71

Got it now! Thank you!

[digital-91]

Hi, Roberto and Larry,

I put photos and PCB pattern jpg here.
http://sutonpu.hatenablog.jp/entry/2014/06/11/211409

Yes, I finally succeeded in transforming from .xps to .jpg. :-)
I takes a long time to find out the way ...

good luck.