Mutron Flanger dissection.

[armdnrdy]

@Larry

Taking another look at your main board layout, the In/Out jack(s) Grounding scheme looks funky. Where exactly do the In and Out jacks find the Ground for the Rings/Sleeves?

I see they are tied to some of the ICs and some resistors but, I do not see where they are tied to the Ground plane  

If you take a look at the schematic...the IN/OUT jacks are connected to signal (virtual) ground.

I had Dino verify these physical connections on his flanger.

The ground plane is "power ground."

And now for some good news.
I received the seven different types of LDRs today....so when I get back from work (Yes! I have a job!) I'll run some tests to find the best one for this circuit. These are all readily available on ebay from foreign and domestic (USA) sellers.

[Govmnt_Lacky]

If you take a look at the schematic...the IN/OUT jacks are connected to signal (virtual) ground.

I had Dino verify these physical connections on his flanger.

The ground plane is "power ground."

And now for some good news.
I received the seven different types of LDRs today....so when I get back from work (Yes! I have a job!) I'll run some tests to find the best one for this circuit. These are all readily available on ebay from foreign and domestic (USA) sellers.

Gotcha! 

Good luck with further testing! Im sure you will find some winners.

[armdnrdy]

Well....

I tried three of the most likely LDR candidates and was anything but impressed.

When the pedal was brought from heel down (lower voltage) to toe down (higher voltage) it would take two to three seconds to reach the target voltage.

The GL55 series of LDR is supposed to have a response time of rise 20ms and fall 30ms. What I was reading was not in this ball park.

So....I took another look at some of the LDRs I had on hand. I gave the Waitrony another try.

I found that with a 5mm, diffused, yellow LED, and extending the shutter slot a bit more, I could match the heal down/toe down voltages of Dino's Flanger. (toe down 11.6V heel down 2.29V)

I took notes of the location of the components on the test board and made the appropriate changes to the LED/LDR board file.

I found that to achieve these voltages, the LED and the LDR have to be adjusted up or down a bit relative to the board plane.

[Govmnt_Lacky]

@Larry

Im guessing this is where the whole clunky LED/LDR light tube comes into play. I am confident that there are LDRs that are available to perform the task without it though 

[armdnrdy]

@Larry

Im guessing this is where the whole clunky LED/LDR light tube comes into play. I am confident that there are LDRs that are available to perform the task without it though 

I think one of the main purposes of the "clunky LED/LDR light tube" is to keep out any ambient light and light produced by the onboard indicator LEDs.

I did try putting the main LDR in a small piece of black "Papermate" pen tube which helped when I tested it for ambient light.
Without the tube, the toe down voltage can drop around two volts. (worst case scenario)

This voltage drop will be audible as a change in frequency.
I think the set up in the Morley isn't as critical because it would be a slight volume drop. If the ambient light stayed constant it would  most likely go unnoticed.

If who ever want to build this thing doesn't mind sourcing a Papermate fine point pen, then I can make provisions on the board for the inclusion of this "light tube".

[digi2t]

Larry, I had the same worry about ambient light from all the indicator LED`s affecting my LDR`s in my Infinitphase clone. In the end, three or four coats of black nail polish on the backsides solved that problem.

In case you haven`t seen how many indicator LED`s there are on an Infinitphase... check it out. Don`t think we have much to worry about here.

[armdnrdy]

Larry, I had the same worry about ambient light from all the indicator LED`s affecting my LDR`s in my Infinitphase clone. In the end, three or four coats of black nail polish on the backsides solved that problem.

In case you haven`t seen how many indicator LED`s there are on an Infinitphase... check it out. Don`t think we have much to worry about here.

The Infinitephase may not have been affected by the indicator LEDs but as far as ambient light (bright sun outdoors, stage lights, etc) the Infinitephase is housed in an enclosure without a "shutter" slot.

I have a industrial lighted magnifier mounted on my work bench. When I moved the lighted "head" around the Morley enclosure, the voltage in the dark (toe down) position would drop as much as two volts. The light is entering the slot from certain angles.
When I put the LDR in the rear of a small piece of "pen" tube.....this fixed the problem. The tube shields the LDR from light entering the slot, only allowing the LDR to be affected from light emanating from a source in front of the tube.

Dino,
Question....
You put black nail polish on the backsides of what? The LDRs or the indicator LEDs?

[wavley]

Larry, I had the same worry about ambient light from all the indicator LED`s affecting my LDR`s in my Infinitphase clone. In the end, three or four coats of black nail polish on the backsides solved that problem.

In case you haven`t seen how many indicator LED`s there are on an Infinitphase... check it out. Don`t think we have much to worry about here.

The Infinitephase may not have been affected by the indicator LEDs but as far as ambient light (bright sun outdoors, stage lights, etc) the Infinitephase is housed in an enclosure without a "shutter" slot.

I have a industrial lighted magnifier mounted on my work bench. When I moved the lighted "head" around the Morley enclosure, the voltage in the dark (toe down) position would drop as much as two volts. The light is entering the slot from certain angles.
When I put the LDR in the rear of a small piece of "pen" tube.....this fixed the problem. The tube shields the LDR from light entering the slot, only allowing the LDR to be affected from light emanating from a source in front of the tube.

Dino,
Question....
You put black nail polish on the backsides of what? The LDRs or the indicator LEDs?

You can minimize ambient light through the slot by using felt like they do on EQ's and mixer faders.

[armdnrdy]

You can minimize ambient light through the slot by using felt like they do on EQ's and mixer faders.

Yeah, good idea!

The thought of something blocking light from entering the slot defiantly crossed my mind.
What was that fiber used for automatic transmission shifters on cars back in the 70s? 

Black felt might not be a bad idea.

[Govmnt_Lacky]

You can minimize ambient light through the slot by using felt like they do on EQ's and mixer faders.

Ahhhh... Now i see the light (No pun intended)

So the ambient light that is effecting the test is coming from the slot that the shutter enters and exits from. Is that correct Larry?

I guess this isnt much of a concern for the Morley-style wahs and volume pedals  

[armdnrdy]

I guess this isnt much of a concern for the Morley-style wahs and volume pedals  

Maybe Morley accepts this as a "slight" design flaw.

Musitronics did something about it by encasing the LEDs and LDRs in ambient light suppressing tubes.

[armdnrdy]

Just to satisfy any curiosity....the reason the Waitrony LDRs work in this circuit now is because I changed to a yellow diffused LED.

I tried the original red diffused that was used in the pedal circuit with assorted LDRs and wasn't getting optimum results, so I switched to green....which is the best color light for LDR perception.

The green worked well on some LDRs but with the Waitrony I couldn't get the correct heel down voltage as the LED was too bright. The Waitronys "light on" resistance is fairly low and I had run out of trimmer adjustment to lesson the LED intensity. I tried moving the LDR away from the shutter/LED but still wasn't able to hit the voltage "mark"

Last night after the GL55 series failed miserably... I had the thought to try a yellow LED with some of the previous LDRs I had tested. LDRs are less responsive to the color yellow...so in theory....the LDR shouldn't perceive as much light. Less light equals higher resistance.

Well...this time "theory" worked! I have adjustment left on the trimmer and was able to move the LDR closer to the Shutter/LED.  

And everyone lived happily ever after!  

[digi2t]

Dino,
Question....
You put black nail polish on the backsides of what? The LDRs or the indicator LEDs?

On the front side of the LDR`s.
















(Fish on!  )











Backsides of the LED`s. That kept the indicator LED`s light from illuminating into the enclosure. Sorry, should have been more clear.

[armdnrdy]

I just walked in from an exceptionally hard day at work.......and you had me!

Black nail polish on the front of the LDRs. 

[armdnrdy]

I reworked both boards to include Molex KK type right angle wafer connectors for the off board wiring.

I Made up a BOM and have started ordering parts. We're getting closer!  

Main board:




LED/LDR pedal control board:



What looks like oversized mounting holes for the LED/LDR board are actually "keepouts" providing a separation from the Morley enclosure and the board's power ground. The enclosure's mounting posts have a 6/32 nut directly under these locations.
The enclosure will be "grounded" with the "signal" ground.

[Govmnt_Lacky]

Soooooooo want to build this! 

[digi2t]

Soooooooo want to build this! 

I feel ya bro.

Fantastic work Larry. Top notch. Can't wait to hear this sucker, just so I can compare it to the original.

[Govmnt_Lacky]

Fantastic work Larry. Top notch. Can't wait to hear this sucker, just so I can compare it to the original.

Just so you can compare it to the original??
Just so you can compare it to the original?? 

I wanna hear this baby so I can know what it sounds like when I build one!!!   

Dino and Larry.... you guys are ACES!!! 

[armdnrdy]

For those of you that have been involved in or have been following this thread.....here's an update:

Worked through a couple of issues with the gracious help of R.G. There were problems transitioning from the "stand alone" power section of the original Mutron Flanger to the power supply I had in mind.

The thread is here: http://www.diystompboxes.com/smfforum/index.php?topic=104370.0

The problems are solved and I'm just waiting on a parts order.

Here is the latest (and I hope the last!) board revision:



I moved a few things around, moved IC6 and surrounding components to the upper left side of the board, added pads for trace side calibration test points, and changed the power section, (half wave rectifier and 1000µf filter cap)

[armdnrdy]

And here is the reworked LED/LDR board.

You will notice that the large "keep outs" have been changed. We now want the power ground to make contact with the enclosure.