MXR - Micro Chorus  [schematic]

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Scruffie
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Post by Scruffie »

Speeddemon wrote:I just received a brand new reissue Micro Flanger;

I also have an original, which has the Reticon 5106 IIRC (though I have seen them with the SAD 512 as well), but the reissue has the V3204D chip.
Footswitch is an Alpha DPDT by the way, and I've read a few times that new MXR pedals that say 'True Hardwire Bypass' have in fact a true bypass switching method, using the Millenium bypass for the LED.
In the reissue Micro Flanger I also spotted a TI 4069UBM.
Post some Gut Shots up!

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Post by distortion_gfx1 »

Speeddemon wrote:I just received a brand new reissue Micro Flanger;

I also have an original, which has the Reticon 5106 IIRC (though I have seen them with the SAD 512 as well), but the reissue has the V3204D chip.
Footswitch is an Alpha DPDT by the way, and I've read a few times that new MXR pedals that say 'True Hardwire Bypass' have in fact a true bypass switching method, using the Millenium bypass for the LED.
In the reissue Micro Flanger I also spotted a TI 4069UBM.

nice.. i would like to see what ic they use...

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Post by Fender3D »

theehman wrote:I don't suppose this new board will fit into an old MXR Micro-Chorus housing? I have 3 w/ bad SAD512Ds.
I reworked on this 'cause some requests...

I redrawn the schematic, some minor changes from mictester's http://www.wizardinside.it/foto/schemi/ ... _schem.pdf
m_chorus_schem.png
Then PCB, it'll fit into MXR's boxes http://www.wizardinside.it/foto/schemi/m_chorus_PCB.pdf.
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Post by akudedde »

Fender3D wrote:
theehman wrote:I don't suppose this new board will fit into an old MXR Micro-Chorus housing? I have 3 w/ bad SAD512Ds.
I reworked on this 'cause some requests...

I redrawn the schematic, some minor changes from mictester's http://www.wizardinside.it/foto/schemi/ ... _schem.pdf

Then PCB, it'll fit into MXR's boxes http://www.wizardinside.it/foto/schemi/m_chorus_PCB.pdf
noob here.. :D...no mean to bump...but thank you verry much for the schematic... :applause:
gonna try to build this

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Post by mictester »

akudedde wrote:
noob here.. :D...no mean to bump...but thank you verry much for the schematic... :applause:
gonna try to build this
Not meaning to be rude - but how much of a beginner are you? I really wouldn't suggest this as a first (or even fifth or sixth) project! It's a complex project and if it doesn't work first time, you'll need a 'scope to trace the faults! Maybe try some easier projects first....
"Why is it humming?" "Because it doesn't know the words!"

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Post by akudedde »

mictester wrote: Not meaning to be rude - but how much of a beginner are you? I really wouldn't suggest this as a first (or even fifth or sixth) project! It's a complex project and if it doesn't work first time, you'll need a 'scope to trace the faults! Maybe try some easier projects first....
thanks for the input :)
just say i know fair enough about the components, but if i'm bad at it.. I'll take the risk...no guts no glory..:D
or..if i'm keeping fail with this project..i'll try easier project like you said :D
thanks :)

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Post by moose23 »

Hey I'm wondering/hoping if maybe someone here could help me, I have an old Micro Chorus here and I'm getting no delay signal. I've traced signal to the input of the SAD512. I've also traced clock from the TL061 and along the way at one of the transistors it changes from a steady thump to a low volume high pitched squeal. Basically I'm wondering is the clock signal supposed to do this which would mean the SAD512 is dead or perhaps hopefully it's something else that's the problem.

Cheers Moose

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Post by Fender3D »

TL061 IS the LFO, it does just modulate the clock...
...clock provided by the astable oscillator build with Q3 and Q4 (if you follow my schematic).

Check the clock (almost) square waveform at SAD's pin 1.

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Post by moose23 »

Fender3D wrote:TL061 IS the LFO, it does just modulate the clock...
...clock provided by the astable oscillator build with Q3 and Q4 (if you follow my schematic).

Check the clock (almost) square waveform at SAD's pin 1.
I know the TL061 is the LFO, problem is that I was using an audio probe last night and could hear a square wave type throb from TL061 that doesn't make it all the way to SAD's pin 1. Guess I need to get it on a scope today and have a look and see if that high pitched squeal is a square wave? cheers for the help so far.

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Post by Fender3D »

TL061's triangular wave won't reach SAD's pin 1,
never.

At pin 1 will arrive the clock from Q3's collector.
This is the signal you must check. You won't hear it with an audio probe 'cause it is tenths of KHz...

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Post by moose23 »

Fender3D wrote:TL061's triangular wave won't reach SAD's pin 1,
never.

At pin 1 will arrive the clock from Q3's collector.
This is the signal you must check. You won't hear it with an audio probe 'cause it is tenths of KHz...
That makes total sense. I could hear a hiss which would be that tens of KHz, checked on the scope and there was an almost square wave there at pin 1 of the SAD so I guess it must be the SAD that died. My friend isn't going to be too happy when I tell him it's an unobtainable part. Thanks again for your help.

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Post by bucksears »

Fender3D wrote:
theehman wrote:I redrawn the schematic, some minor changes from mictester's http://www.wizardinside.it/foto/schemi/ ... _schem.pdf

Then PCB, it'll fit into MXR's boxes http://www.wizardinside.it/foto/schemi/m_chorus_PCB.pdf
Bumping this one - has this schem been verified? (I'd like to take a crack at doing a single-sided version)
If this is good, any volume issues when the effect is on? I love the demos I've heard of the Micro Chorus reissue, but there have been reports of a volume increase when the chorus is on.

Thanks

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Post by Fender3D »

Schematic verified :thumbsup
I can't tell how much similar to original micro-chorus though.

Do not trust reports about volume increase or drop with pedals, unless you don't try it yourself...
Changes in volume depend on several factors, expecially the amp you use...

With my old plexies, I never noticed volume issues with MXR pedals.

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Post by bucksears »

Thanks!

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Post by GodSaveMetal »

bucksears wrote:
Fender3D wrote:
theehman wrote:I redrawn the schematic, some minor changes from mictester's http://www.wizardinside.it/foto/schemi/ ... _schem.pdf

Then PCB, it'll fit into MXR's boxes http://www.wizardinside.it/foto/schemi/m_chorus_PCB.pdf
Bumping this one - has this schem been verified? (I'd like to take a crack at doing a single-sided version)
If this is good, any volume issues when the effect is on? I love the demos I've heard of the Micro Chorus reissue, but there have been reports of a volume increase when the chorus is on.

Thanks
Please Bucksears; I´m waiting your single side PCB one´s; my cases are 80mmx120mmx40mm ; I also made some pedals all in one!! without cables; and made my own 3pdt; DIY "3pdt MADE IN PERÚ" it´s 5º generation !! yeahhhh!!!!!

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Post by bucksears »

I'm slammed with work this week & busy this weekend, but will probably start on it probably a week from today. I'll post updates as I go.

Thanks,

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Post by GodSaveMetal »

bucksears wrote:I'm slammed with work this week & busy this weekend, but will probably start on it probably a week from today. I'll post updates as I go.

Thanks,
OK thanks man; THANKS!!! :thumbsup I stay tunned!!! :mrgreen:

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Post by bucksears »

Ok, this one might have to wait (for good reason 8) )
I've gotten to where my vintage Ibanez CS-505 (808-era) is really shining as far as a warm, shimmering, non-midrangey chorus that actually plays well with distortion. So, I'm going to start tracing it so I can rebuild it with a potential fix (on-board trimmer) for the volume bump when engaged. (I don't want to risk killing an otherwise perfectly functioning vintage chorus pedal)

Didn't mean to hijack this thread, but it's kind of an update on why I'm putting the Micro Chorus PCB on hold.

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Post by bucksears »

Well, the CS-505 turned out to be a bit more complicated than I wanted to mess with right now. So, the MXR Micro Chorus is back on.
I'm about 2/3 done with the PCB. I'm trying to keep it 2" wide and around 2 to 2 1/2" long. I'd like to be able to fit it in a 125-B enclosure.

Two things:
1) Referencing Fender3D's schematic, I would like to see where I might be able to add a trimpot to adjust the effect level and POSSIBLY add a depth control pot to mount externally. If I can't add a depth control, that's fine; people seem to like the simplicity of the original design. The level control is more important, though.
2) I need someone to check over the layout when I'm done - I don't want to post something officially until it's been verified.

Thanks,
Buck

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Post by Fender3D »

bucksears wrote: 1) Referencing Fender3D's schematic, I would like to see where I might be able to add a trimpot to adjust the effect level and POSSIBLY add a depth control pot to mount externally...
Hi Buck,
R17 will set the wet level, you might as well place a balance sort of lowering R16 and R17 wiper to U1 pin 6. You won't have a huge usable range though...
Otherwise you may use a pot instead of R20.
There's no easy way to have a depth control, unless you put a buffer after LFO.
If altering delay (therefore working range) is enough, you may change R28/R34 ratio.

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