Mutron Flanger dissection.

[armdnrdy]

Federico,

Updated for completeness. 

[Fender3D]

 

call me pickyrico....

but to sub it for a SAD you can avoid trimmer and capacitor....

I swear this is my last nuts breaking about this... 

[armdnrdy]

Which trimmer? The emitter trimmer or the balance trimmer?

Isn't the .47µf cap (C19) and R22 to signal ground/ref constructing a R/C filter?

[Fender3D]

Which trimmer? The emitter trimmer or the balance trimmer?

The emitter one, so you can use R21/R80 instead

Isn't the .47µf cap (C19) and R22 to signal ground/ref constructing a R/C filter?

Yes, R22 provides Z2a bias also. But those parts are on MuTron board already...

[armdnrdy]

Hey Frederico.

I'm not designing the daughter board for Dino.....I just drew a few options for the output. I showed that for MN3007 testing purposes you don't really have to add the balance trimmer...there's a simpler way to do it.

I thought you meant to take the .47µf cap and trimmer out of the schematic altogether!  

[digi2t]

Updated the original schematic. I forgot to correct C50. Thanks to Larry for the pointer.



Although I'm confident that it's kosher, Larry will be validating my trace.

[Govmnt_Lacky]

@Dino

Wondering if you could post your adapter board work here as well to keep everything in one place. Nice and tidy for dumb searchers like myself! 

Looks like the daughter/adapter board (MN3007) is worked out! Now, its only a matter of finding a way around the LED/LDR arrangement and generating a good PCB (possibly to fit and work in a Morley wah-type enclosure  )

[digi2t]

Damn, sorry... I was in the process of doing so last night, and I got side tracked. I posted it on the other forum, and then some unexpected company showed before I could get the info up here.

I need to aquire some hounds that I can release.

It`ll be up here tonight.

[Govmnt_Lacky]

Damn, sorry... I was in the process of doing so last night, and I got side tracked. I posted it on the other forum, and then some unexpected company showed before I could get the info up here.

I need to aquire some hounds that I can release.

It`ll be up here tonight.

No worries Dino!

I know you are on top of it. This was more for MY purposes since I get lazy 

[armdnrdy]

As a complement to Dino's perf SAD1024 to MN3007 daughter board, here is another version for those who have an itch to etch.





Now could someone please give me a clue how to post a printable board for etching. (which format for best quality and actual size printing)

[armdnrdy]

Here's a link to a JPEG that can be printed actual size with Windows based programs.

https://dl.dropboxusercontent.com/u/53299166/DIYstompboxes/MN3007%20board%20print.jpg

Don't use scaling or "fit picture to frame."

[digi2t]

@Dino

Wondering if you could post your adapter board work here as well to keep everything in one place. Nice and tidy for dumb searchers like myself! 

Looks like the daughter/adapter board (MN3007) is worked out! Now, its only a matter of finding a way around the LED/LDR arrangement and generating a good PCB (possibly to fit and work in a Morley wah-type enclosure  )

Instead of reposting everything again, I'll just put the link here for the daughterboard work;

http://www.diystompboxes.com/smfforum/index.php?topic=103879.msg929707#msg929707

[armdnrdy]

I finished a few projects and cleared my work table off (again) and am ready to start experimenting with a LED/LDR mock up board in the Morley enclosure.

Something occurred to me while searching for a LDR with similar specs. The "light" toe up voltage reading we have (2.23 volts) is always going to be a constant. The "dark" toe down reading (11.89 volts) will vary depending on when the reading was taken.

If the voltage reading was taken the second the pedal was moved to the toe down position...than the reading is accurate. The preferred resistance similar to the original could be calculated from this immediate voltage measurement.

Let me explain.

Light dependent resistors are generally "dark" rated by listing their resistance at 10 seconds after the light has been taken away.
The Mutron Flanger's LDR "dark" resistance is most essential right at toe down, not 10 seconds after toe down. We all know that many LDRs "dark" resistance runs off into the extreme high meg ohms region. That resistance reading is not what we are interested in either.

I am aware that a LDR's resistance parameters can be adjusted using resistors or trimpots but...I would rather do a little "leg" work and get as close as possible to the original specs and experiment with things like distance between the LED and the LDR.

Dino,
When you took the toe down reading, was the voltage a constant 11.89 volts? It seems as if the voltage should gradually move higher as the parallel resistance between the LDR (PC2) and the lower half of the voltage divider (R70 1M) increases.

[Ronan]

Larry, pdf is pretty common for etchable designs, seems to do the job, I believe it is vector-based similar to cad programs whatever that means, very good resolution I think. Are you sure the footprint for TR1 is correct? it looks very compact.

I'm thinking that the LDR's that we used for the EH Talking pedal conversion (Waitrony KE-10720) might be suitable for the job. I fooled around with one, and although it gives a lower light resistance, about 5K in similar conditions, the speed up to 40M dark is pretty similar to the originals. Besides, this could be fine tuned with resistors, LED selection, LRD angle, and there is a range trimmer as well. Nothing insurmountable here.

+1 the Waitrony LDR has been a gift to pedal builders, pretty hard to go wrong with it IMO. If you delve into the depths of testing response times, yes, it will take time to settle, like most other LDR's, but it sure works well in treadle fx pedals and has a fast initial response. 24c ea plus 99c shipping last time I ordered, that was a while back though.

[armdnrdy]

Hey Ian,

Eagle has the option to save the file as a PDF which I tried...the print wasn't to scale.  
The T-1 trimmer is the standard 3362P device file in Eagle which I've used countless times with no fit problems.


The Waitrony LDR is definitely not off the table by any means. We should gather as much info as we can so we can have a starting point of what to shoot for.

Last night I listened to the sound sample again and got completely reenergized! This is a very cool sounding beast! I'm excited about this project!  

[Ronan]

Yep TR1 footprint is correct, I've never used 3362P before, now I know...

I usually put a scale on the drawing so you can measure the printed result, then scale it accordingly, pdf certainly has the resolution though.

[digi2t]

Dino,
When you took the toe down reading, was the voltage a constant 11.89 volts? It seems as if the voltage should gradually move higher as the parallel resistance between the LDR (PC2) and the lower half of the voltage divider (R70 1M) increases.

You bring up an important point here. When I took the readings, the were withing 2 or 3 seconds, but more importantly, the readings are wide open / fully shut. The board is out of the unit, and the shutter is part of the enclosure, so I had to resort to using a machinists ruler as a shutter. Not ideal, but it gives us the absolute extremes. If you wish, I can remount the board, and measure again using the actual travel. And, if it`s important, I can take initial readings, and 10 second readings.

Luckily, my DMM display has a backlight, and I did take the readings in complete darkness, so I`m sure that my readings aren`t being faux`d by any external light.

Would this help validate things?

[armdnrdy]

If you wish, I can remount the board, and measure again using the actual travel. And, if it`s important, I can take initial readings, and 10 second readings.

Would this help validate things?

Hey Dino,
Yes, when you get the time that would be the best for measurements...under actual working conditions.
A measurement from when the toe is up, to the first voltage your DMM registers right after the toe is dropped down.
The second measurement, 10 seconds after the first measurement.

I think this info will definitely help the cause in choosing a close LDR.

I'm working on a test board that will fit the mounting holes and shutter/slot configuration of the Morley. It will be the complete Mutron pedal circuit with multiple socketed pads for varying the distance of the LED/LDR.

[armdnrdy]

Dino,

I just thought of something.
when your taking measurements of the flanger, I need one other voltage measurement. The voltage at Z10A pin 3.

That's the voltage that the voltage divider is supplying to pin 3 after you adjusted the trimmer (R78) for the pedal sweep adjustment.
From what I gathered, this voltage controls the brightness of the LED, so I should try to match the output voltage (high and low) of Z10B with the trimmer (R78) adjusted to produce a similar voltage/brightness.
Make sense?

[digi2t]

I'm going to get the unit together tonight. Overtime till 10PM last night, so it was "Welcome to Zombieland".

I'll get the requested voltages, though I don't see Z10B voltage/brightness thing being completely truthful, unless we have the identical LED/LDR combo, which we won't. Quite honestly, I think the range will be somewhat of a "adjust to taste" deal. Some folks like it a bit higher, and some a bit lower. I'll record it nonetheless, since it will maybe provide a decent jumping off point.