# The Mesmerizer   ( weird pedal )



## griff10672

I renamed this one ... based off of a old Three Stooges episode ..... anyway .... really cool ... weird pedal ... sounds like a overdrive sort of ... with some tremelo kinda .... lol ... I've only messed with it for 10 minutes or so ... 

side note : I thought the Bicolor LED would do something besides just light up .... maybe I messed up but it looks just like both sides of the LED are on at the same time when I turn it on ....  I thought it would flicker between colors or something based on the rate ... anyone know anything about this one ??


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## Jovi Bon Kenobi

HOT! Neat design!


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## Mourguitars

Looks fantastic !

Mike


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## griff10672

Jovi Bon Kenobi said:


> HOT! Neat design!


that " hot " pink is a cool color !


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## griff10672

Mourguitars said:


> Looks fantastic !
> 
> Mike


Thanks Mike !


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## Robert

griff10672 said:


> side note : I thought the Bicolor LED would do something besides just light up .... maybe I messed up but it looks just like both sides of the LED are on at the same time when I turn it on ....  I thought it would flicker between colors or something based on the rate ... anyone know anything about this one ??



The LED should cycle back and forth between the two colors along with the LFO.


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## Barry

Looks great!


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## griff10672

Robert said:


> The LED should cycle back and forth between the two colors along with the LFO.


It's staying solid for both colors .... The pedal is amplifing the signal ....  but has no effect ......I'm assuming the LFO isn't moving / working .... I re checked all component values everything looks fine .... don't know what voltages I should have ... I was getting 1.95 and 1.65 on either legs of the bi color LED ... but no flicker ... and no effect ...  don't know enough to know where else to look .... in my experience building other pedals with LFO's this has happened to me when something was touching something it shouldn't have ... like 2 legs of an IC being soldered together by accident .... I've looked all over all my connections can't find any bad solder joints or wrongly married ones ... .... making me think the chip is a fake .... I bought 5 ... and have tried 3 of them ... same results ...


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## Robert

Where did you get the XR2206?    I'd be suspicious of that.

I've built a few of these over the years from etched boards, vero, and this PCB...    The most common culprits (aside from bad solder connections / shorts / etc) are the two 2N5457 transistors and the XR2206 IC.     If the problem was the 2N5457's the LED would still cycle like it should.


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## griff10672

Robert said:


> Where did you get the XR2206?    I'd be suspicious of that.
> 
> I've built a few of these over the years from etched boards, vero, and this PCB...    The most common culprits (aside from bad solder connections / shorts / etc) are the two 2N5457 transistors and the XR2206 IC.     If the problem was the 2N5457's the LED would still cycle like it should.


thanks for the quick reply ...... I think I actually grabbed them from Amazon .... China seller with decent ratings ... how would I even go about finding if they are fake ?


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## Robert

Start by verifying that you have 9V on pin 4, and 0V (ground) on pin 1.

If you have an oscilloscope you can check for the LFO waveform on Pin 2.

If not, you can use your DMM.
You should see a fluctuating voltage (the LFO output) on Pin 2, adjusting the Rate control should change how fast the voltage changes.


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## griff10672

0V on Pin 1
8.79V on pin 4
no scope here ....
All the way counterclockwise on the rate gets me 2.30V
all the way clockwise gets me ( started at 2.87 V slowly climbed to 3.07 V )
yes the voltage was moving ...
the rate pot doesn't seem to do much ... the voltage just really slowly climbs ...


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## geekmacdaddy

Looks beautiful, Griff. As always. You'll get it sorted.


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## griff10672

I think I might have bought some bad chips .......seems all the pedals I want to build have obsolete and hard to find chips or trannies .....lol ....ugh


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## music6000

griff10672 said:


> I think I might have bought some bad chips .......seems all the pedals I want to build have obsolete and hard to find chips or trannies .....lol ....ugh


This is a* Must Have* for Pedal Building !!!     *PEAK DCA55 Semiconducter component analyser*
Video Link below:


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## zgrav

a seller on amazon has 2 of the XR2206 chips for less than $6 with free shipping if you wanted to diversify your shopping risks.


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## griff10672

zgrav said:


> a seller on amazon has 2 of the XR2206 chips for less than $6 with free shipping if you wanted to diversify your shopping risks.


yeah ...... I saw that .... pretty sure I got the five I have from them ....  I'm ordering two from a company here in the states ... we'll see what happens 

thanks for the heads up though


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## griff10672

music6000 said:


> This is a* Must Have* for Pedal Building !!!     *PEAK DCA55 Semiconducter component analyser*
> Video Link below:


holy crap .... I was just literally looking at that same thing ..... I should pull the trigger on one

I'd like a way to test chips though .....


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## music6000

griff10672 said:


> holy crap .... I was just literally looking at that same thing ..... I should pull the trigger on one
> 
> I'd like a way to test chips though .....


I've had my DCA55 for nearly 3 years, Same Battery, also great for testing Diodes, Dead or Alive!, DCA75 is the next step up.
Look at the PEAK website, They might have one for CHIPS!





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						Test Instruments | Peak Electronic Design Limited
					





					www.peakelec.co.uk


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## griff10672

music6000 said:


> I've had my DCA55 for nearly 3 years, Same Battery, also great for testing Diodes, Dead or Alive!, DCA75 is the next step up.
> Look at the PEAK website, They might have one for CHIPS!
> 
> 
> 
> 
> 
> __
> 
> 
> 
> 
> 
> Test Instruments | Peak Electronic Design Limited
> 
> 
> 
> 
> 
> 
> www.peakelec.co.uk


I think I'm going to get one either way ..... I'm assuming it would be great for building fuzzes ....


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## Jovi Bon Kenobi

I bit the bullet and picked one of those up recently. No regrets!


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## griff10672

Jovi Bon Kenobi said:


> I bit the bullet and picked one of those up recently. No regrets!


seems like almost a necessary piece of gear the more I think about it


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## geekmacdaddy

music6000 said:


> This is a* Must Have* for Pedal Building !!!     *PEAK DCA55 Semiconducter component analyser*
> Video Link below:


Had one for a LOT of years. even resoldered one of  the leads. Couldn't live without it.


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## griff10672

OK .... the pressure from my peers is to much .... ordering one now ....... lol


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## griff10672

Interesting info I found on the XR2206 chip from someone else that had problems .... funny ... the five chips I bought all have the F0919 # on them .... which this guy states his issues with ( that seem to make sense involving my pedal not functioning properly ) 
so I found a place here in the states that carries the F0918 branded ones for 8.00 a piece ... expensive I know .... but if they work it will be worth it to me anyway ... I included the info I found below ... just in case someone else might be thinking about building one .





 " Recently smoked this chip in an analog/Digital Trainer and ordered some replacements on line, none of them worked in the existing circuit. I downloaded the data sheet for the chip and breadboarded the sample circuits and tried the chips in them, with little or no success. Eventually I found by adjusting the supply voltage, and the values of the external resistors and caps I could get them to a least partially function. I noticed that the original chip had a batch number of F0918 and the ones I received had a batch number of F0919 and were from china. I had a second Function Generator that used the same chip, so I pulled it and tried it in the unit I smoked the chip in and it works just fine. I than tried it in the test circuits from the data sheet and it also worked fine in them. I found a source for the chips stateside, called and customer service checked stock and confirmed their stock had batch number F0918. Ordered and received them they work just fine.

Bottom line here is my experience with the china version of XR2206 is the external components must be custom selected for the particular chip and will not work as a suitable substitute for XR2206cp F0918. Also, I was never able to get the FSK circuit on the china version to work no matter what I did.

I know the previous posts regarding this chip are old but since china started making this chip maybe this will save some people some time and aggravation.    "


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## zgrav

Very interesting post.  I build a simple signal generator with this chip several years ago.  I ordered a couple of the chips from Amazon and will see if they work if I swap them into the signal generator.  Based on the info above I won't be surprised if they are not working substitutes for the older chip.


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## Robert

Coincidentally I just had a friend email me last night with troubles on a Mesmerizer build.   I suspect the XR2206 is the issue with his as well.

He has reordered another IC from Jameco, they're a bit more expensive but most likely legit parts.

I'll follow up when I hear back.


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## griff10672

Robert said:


> Coincidentally I just had a friend email me last night with troubles on a Mesmerizer build.   I suspect the XR2206 is the issue with his as well.
> 
> He has reordered another IC from Jameco, they're a bit more expensive but most likely legit parts.
> 
> I'll follow up when I hear back.


I ordered a few from Jameco myself the other day .... won't be in till Tuesday though ..


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## Robert

griff10672 said:


> I ordered a few from Jameco myself the other day .... won't be in till Tuesday though ..



XR2206 from Jameco (with batch number F0918) cleared up the problem, hopefully that'll take care of yours too.


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## griff10672

Robert said:


> XR2206 from Jameco (with batch number F0918) cleared up the problem, hopefully that'll take care of yours too.


perfect !!! Thanks ...


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## griff10672

Robert said:


> XR2206 from Jameco (with batch number F0918) cleared up the problem, hopefully that'll take care of yours too.


All set !!!   circuit worked as soon as I popped the new chip in .... 

This is the first time I've got burned buying chips .... 

Beware of XR2206 marked with batch # F0919 they are bogus ... I purchased them from Amazon

Jameco here in the states has legit ones .... marked F0198


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## Robert

Excellent!   I'll have to make a note of this in the build docs.


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## Chuck D. Bones

Love the name & the graphics!  
Maybe the LFO is running too fast?  Verify C12 is 4.7uF and the RATE pot is not shorted.  Or maybe the DEPTH pot is shorted?  Been a very long time since I used XR2206.  If memory serves, C12 should not be a polarized cap.  According to the data book, the voltage on the timing cap swings both directions.


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## zgrav

The XR2206 datasheet says c12 is a timing capacitor that can go up to 100uF with no comment about making sure it is not polarized.


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## Chuck D. Bones

I've seen it done both ways; with polarized electrolytics capacitors and with back-to-back electrolytics.  The EXAR Function Generator Databook is silent on the use of polarized capacitors.  It does contain this simplified schematic of the oscillator which shows the capacitor waveform swinging positive and negative, but it's only 2 Vbe peak-to-peak.  Usually takes more than that to make polarized capacitors leak current.


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## ch ra

griff10672 said:


> All set !!!   circuit worked as soon as I popped the new chip in ....
> 
> This is the first time I've got burned buying chips ....
> 
> Beware of XR2206 marked with batch # F0919 they are bogus ... I purchased them from Amazon
> 
> Jameco here in the states has legit ones .... marked F0198



Hmm, is this batch number definitely bad? I got a chip from EBay marked F0919 and my build is a great boost pedal but does not put out any tremolo. I'm unsure whether it is a problem with the chip or with the JFETs (I used one SMD and the others were through hole). If it's certain that batch number is bad or fake, then it should be straightforward to deal with the vendor on Ebay.


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## griff10672

ch ra said:


> Hmm, is this batch number definitely bad? I got a chip from EBay marked F0919 and my build is a great boost pedal but does not put out any tremolo. I'm unsure whether it is a problem with the chip or with the JFETs (I used one SMD and the others were through hole). If it's certain that batch number is bad or fake, then it should be straightforward to deal with the vendor on Ebay.


yeah man ......... your having the exact same problem I had ............ F0919 are crap-ola


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## zgrav

I haven't seen anyone reporting that a chip with that batch number works.  I bought a couple of them recently and they were bad.


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## Chuck D. Bones

Maybe the real solution is to design in an oscillator built with parts we can buy today.  With a quad opamp, some diodes and a handful of Rs & Cs, we can have sine, triangle and squarewave.

Another alternative would be to write FV-1 code that emulates the Mesmerizer.


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## Robert

Chuck D. Bones said:


> Maybe the real solution is to design in an oscillator built with parts we can buy today.  With a quad opamp, some diodes and a handful of Rs & Cs, we can have sine, triangle and squarewave.
> 
> Another alternative would be to write FV-1 code that emulates the Mesmerizer.



The Harmonic Tremolo FV-1 patch is fairly close.

I've been meaning to yank out that XR2206 for a while...   I started monkeying around with a version that uses an ATTINY for the LFO but it has fallen through the cracks for now.


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## tdukes

I also have no oscillation with XR2206 marked F0919. I got them off eBay from some guy in the Fiji islands. 

I just ordered two from Jameco. 

This is the same chip the signal generator I ordered off Amazon uses. I am paying as much for the chip as for an assembled and boxed signal generator.

Todd D.


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## moonlightpedalbuilds

Got mine from China. No good! Ordering from jameco is not an option for me. I am from Manila, Philippines. $18 just for shipping.

Apparently F0919s needs to be tweaked for it to work. Anyone has any idea on how to do this?


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## ch ra

Hello, I bought my second chip off Ebay, this time from a US seller that seemed to be pretty reputable. It was also a FO919 which was different from the picture, and there's no oscillation. Makes for a fantastic sounding boost, but not a tremolo, haha

Before I complain to them though, I want to make sure I haven't done anything wrong--there's like a million jfets in there, and I initially had shorted two of the legs of one of them because I forgot to trim them before I tested the PCB. Also, there is one SMD jfet, and who knows maybe I soldered that wrong. 

I can post pic of pcb but is there any way to check if the IC is bad? Should I just assume that the 0919s do not work?


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## zgrav

Just because the 0919s reported on here were bad does not mean that all of the 0919s are bad.  maybe the bad ones we have seen are counterfeit copies of good 0919 chips.

but no easy way to test it except by putting it into a working project.

the two jeft transistors at Q5 and Q6 were the key to getting my build working.  I only had 3 transistors that would work in either of those spots and that is from over a dozen or so transistors that should have worked in them.


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## tdukes

Do you have any way of measuring and reporting the bias voltages from your working example? 

Can you distinguish between the working and non-working transistors at Q5 and Q6 other than they worked?

I am still trying to get my mesmerizer to work now that I have the F0918 and the LFO is working somewhat. 

See my thread at: https://forum.pedalpcb.com/threads/mesmerizer-led-flickering-but-no-modulation-of-sound.1523/


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## zgrav

I had everything working in my build except the modulation, and I knew my xr2206 chip was good because it worked in another project.  The mesmerizer is a bit picky for Q5 and Q6, but I can't tell you what the magic sauce was for the ones that worked.  I have since used some of the transistors that would not work in the mesmerizer in another project where they work fine.   

Here is the thread where I was discussing the issues I had:  https://forum.pedalpcb.com/threads/not-so-mesmerizing-mesmerizer.1225/

From your other thread, when you have the xr2206 output on the oscilloscope, does the waveform change shape when you are adjusting the rate and depth controls?   You can also open the connection betwen pins 13 and 14 to turn the sine wave output into a triangle wave that has a higher output, so you could check that on your scope too.


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## tdukes

zgrav said:


> Here is the thread where I was discussing the issues I had:  https://forum.pedalpcb.com/threads/not-so-mesmerizing-mesmerizer.1225/
> 
> From your other thread, when you have the xr2206 output on the oscilloscope, does the waveform change shape when you are adjusting the rate and depth controls?   You can also open the connection betwen pins 13 and 14 to turn the sine wave output into a triangle wave that has a higher output, so you could check that on your scope too.



Thanks! I'll look at your other thread and see if it helps. I don't get a shape change with rate and depth, but the frequency and magnitude do vary.


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## zgrav

seems like your 0919 chip might be working.you can try opening up the connection between pins 3 and 14 to see if you get a higher magnitude triangle wave shape.  my suggestion other than that would be to try multiple transistors in Q5 and Q6.   You can hear a difference immediately when even one of them is working correctly.    

I had a couple of J201s that worked the best, but even then most of my J201s did not work.


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## tdukes

zgrav said:


> seems like your 0919 chip might be working.you can try opening up the connection between pins 3 and 14 to see if you get a higher magnitude triangle wave shape.


I have already swapped the 0919 for a 0918 I got from Jameco. With the 0919 there was no flickering of the LED and the wave at pin 2 was completely flat. I don't remember the voltage, but it wasn't a sine wave.


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## zgrav

Do you have more transistors you can try out in Q5 and Q6?  You also can order some J201 smds soldered onto an adapter board from pedalpcb for $2 each.  I have some of the adapter boards on their way in the mail and plan to see if the smd 201s work in the mesmerizer.


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## tdukes

zgrav said:


> Do you have more transistors you can try out in Q5 and Q6?  You also can order some J201 smds soldered onto an adapter board from pedalpcb for $2 each.  I have some of the adapter boards on their way in the mail and plan to see if the smd 201s work in the mesmerizer.



I have 6 more 2n5485 that look like they came from tayda. I have 2 more 2n5457 that came from who knows where, probably eBay. I would have to look through the rest of my transistors to see if there is anything similar, but I think they are mostly bjt. I bought some J201 recently from mammoth, but I have already used them in the Son of Ben.

I ordered some transistor sockets. I figure if I am going to be swapping out, I don't want to lift a pad re-soldering over and over.


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## ch ra

I have read somewhere that the key to making the 0919 work is to change the input voltage(?). Oddly, when my JFET leads were shorting, I did get tremolo output from the pedal, but I also got endless honking feedback (also with tremolo effect). When I trimmed the leads, it went back to being a boost pedal ?

If there is a fix to get the 919 to work (aside from testing a million JFETs, which I don't have) I'd love to hear it!


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## zgrav

Use your scope and check to see what waveform you are getting at pin 7 on IC1.   Also see if it changes when you are moving the depth and rate pots.  You should also be able to tell the voltage range between the bottom and top of the wave form.

that info might help others make suggestions about tweaking something for Q5 and Q6.


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## Chuck D. Bones

I think I'm lost, is this the *Build Reports* forum or *Troubleshooting*?


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## Nostradoomus




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## zgrav

Chuck D. Bones said:


> I think I'm lost, is this the *Build Reports* forum or *Troubleshooting*?



You?  Lost?   Inconceivable!


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## Chuck D. Bones

I guess it stands to reason if we're discussing the _Mesmerizer_, the topic will turn to troubleshooting sooner or later.


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## ch ra

Sorry I just jumped onto an old thread, but yeah troubleshooting.

So I don't have a scope, but I am pretty sure that the 0919 from Nooelectric has pretty much the same problem as the other 0919 (but they wouldn't take it back). Anyhoo, does anyone have a good source for a 0918? I saw Jameco as one, but that's $8 plus a $5 processing fee, possibly plus shipping. Any other options? Thanks!


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## Robert

zgrav said:


> but no easy way to test it except by putting it into a working project.



If the LED isn't cycling colors there's no need to start pointing fingers at the JFETs (yet) ...       

The bi-color LED should cycle colors even if the JFETs aren't installed.


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## griff10672

Wow ..... you guys are beating this thread into submission ... lol

I must say ... since I switched to the 0918's from Jameco this pedal has become a quick favorite of mine .... very very cool pedal .


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## tdukes

griff10672 said:


> side note : I thought the Bicolor LED would do something besides just light up .... maybe I messed up but it looks just like both sides of the LED are on at the same time when I turn it on ....  I thought it would flicker between colors or something based on the rate ... anyone know anything about this one ??



You could try swapping R17 for a 47K and see if you get more red. I also feel like I got more depth after doing this.


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## griff10672

I'm not touching this circuit ... I love it ...  

but definitely thanks for the suggestion


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## ch ra

Just wanted to say that I finally sourced a US Made XR2206 (Realistic brand! Radio Shack, baby!) and it looks like it works! Was on a bad string of failures, so I really needed this win. Now to figure out how to get the pcb into my disastrously laid out 1590bb (set up for 2 different tremolo pedal pcbs)... 

Thanks for the help, I promise to put future calls for help to troubleshooting page!


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