Recommendations for a complete DIY rack

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Re: Recommendations for a complete DIY rack

Post by KSS » Thu Jun 10, 2021 10:40 pm

Pr0fBi0 wrote:
Thu Jun 10, 2021 7:01 pm
first off, i really appreciate you two helping me out and pushing me towards building modules from scratch. I really liked the clock divider module posted earlier, but i saw the schematic and picture of it and instantly said....nope....that's way above my skill level
One day you will look at that same module and know how to do it!
I can sort of do this now. When something isn't working i do have to dig into the schematic to find the part that isn't working (usually outputs or pots) and trace back in the signal flow and check those parts.
Exactly. You're already doing it!
where my knowledge stops is understanding what each thing in the signal flow does and why.
Th what will come before why for many things. But all of it will depend on what you add to the mix from a resource standpoint. I always suggest reading old synthesizer service manuals. The two online for the ARP 2600 are very good. The service manual for the moog MG-1 is also very good for learning. Reading about how these old mostly simple circuits work will help. Try to read the circuit descriptions provided with any good kit. And if you can't find those read the old ones from MOTM kits or anywhere else you can find them. All the old PAIA manuals are online at their PAIAtalk forum and since these were written for raw beginners, and are very simple circuits, they're easily understood.

But you will also want to begin learning something about electronics in general. For that the forrest mims booklets are good, and RadioShack also has a very good book called Basic Electronics by Gene McWhorter and Alvis J Evans. Their SKU is 62-1394. It doesn't have a Bowkers ISBN but you can still probably find it online at amazon or a place like abebooks.com.
The second book I strongly recommend is Understanding Basic Electronics by the ARRL here:
http://www.arrl.org/shop/Understanding- ... ectronics/
https://www.amazon.com/Understanding-Ba ... 0872590828

Both of these are simple enough and yet detailed enough to get you on a solid path. They also both avoid some of the mistakes I've seen online in many learning electronics websites. Sometimes these aren't technical mistakes, just poor explanations that confuse more than help.

Books are only part of the answer though. You're doing the right thing by building modules! Keep doing that.
i did build the AI synthesis 002 mixer which does both cv and audio. i could try to use that as a basis to make my own design, but i wouldn't know where to begin to make changes to add the features i'd want. the complicated thing about modular is it seems like you don't know what you really want/need out of a module until you get further in and can use some things and start to understand how it all works.
Yes. It will get easier as you use your modules more. That's the REAL beauty and benefit of DIY. It's not a one-time-have-to-get-it-right-forever thing.
You can re-do modules with new panels or kludge in new mods as you learn both what you need or want and also how to do it. A man stranded on a raft at sea once said hunger is a good spice. In the same way having actual modules which are lacking something you want is good reason to learn how to add it!
i'm still trying to understand how mixing cv works. because when i've tried it with the modules i have it did not produce anything like what i was expecting. but i have only messed around with it a little. i've mostly been using the mixer to do boring things like plug my volca sample in and use it for drums.
it's all good. and it's all driving you towards understanding more. As you get more modules -even dup0licates of the same ones- your choices and options greatly increase. As you fix your mistakes -and sometimes the mistakes of the module designer!- you will gain confidence in your ability to fix things which will increase your ability to patch in ways that might have seemed scary before. <--Another big benefit of DIY. If i break it, I can fix it!
which pages were you referring to? the only ones i could find were these two:
http://www.doepfer.de/DIY/a100_diy.htm
were those the ones you mean?
This one. Start with the easiest ones there for you and see how it goes. Do some of the REALLY simple ones too. You might begin to see how these can be used with the more complex modules you're building from kits. Or PCB-Panel sets which introduces the next level of learning and understanding. How to choose and order parts.<--This can be especially intimidating. But it's not as bad when you're doing the layout too, so many mistakes beginners make in size and type can still be used.

I attached a simple EG that I bet you could wire up from the drawing? And once you do, you might wish it could work from a lower gate voltage. Where you might compare it to the AR in the ARP 2600 service manual and see that theirs also needs 10V gate for 10 V output. Which might lead you to look for comparators and what they do. Let your need an curiosity drive you.

Or you might want to skip some of that and try this one using a 555 or 7555 that I bet you can also wire up from the drawing. It's simply begging to be a dual module. <--Why do i say this?

EGs are great for learning because:
- They're mostly simple circuits.
- You can tell whether they're working -or not- and how well -or not- pretty easily.
- They make use of typical circuit blocks that you will see in other modules.
- The end result is useful no matter what size system you end up with.

^Mixers too. For the same reasons.

I also attached Nicolas W's EG. Vero or Stripboard is a nice intermediate step between kits and full PCB layout. At the Electro-music forum there are *many* stripboard designs posted. Look for those whose build is verified.

And finally two simple min max circuits to play with. I bet you can wire these up too!

Rene Schmitz has a bunch of simple and good module designs on his website.
YuSynth too.

The real key is to keep going. Know that things will start to come together for you as you do more. And also that you don't need to know how it all works. At all. <--Many just buy kits and ask questions here about what to do to fix it when it doesn't work. They don't care about the why or how, they just want a module that works. You want that too. But by wanting more, you put yourself on a different path. We'll notice that you care about the why and not only the result. We'll help you get there.
Attachments
Doesn't get much simpler than this.<br />Does it work? How or why?
Doesn't get much simpler than this.
Does it work? How or why?
t_steved_ar_env_983.png (99.28 KiB) Viewed 287 times
Does this have to use 5V? How could you make it for Euro?<br />Why a 7555 and not a plain 555?<br />Could a dual 555 aka 556 be used instead?
Does this have to use 5V? How could you make it for Euro?
Why a 7555 and not a plain 555?
Could a dual 555 aka 556 be used instead?
ad_217.gif (10.31 KiB) Viewed 287 times
At the EM forum, there is much discussion and several known good layouts for this circuit. Along with mods and improvements. But it's very usable as-is here.
At the EM forum, there is much discussion and several known good layouts for this circuit. Along with mods and improvements. But it's very usable as-is here.
This simple circuit -and its partner below- may be more useful than you realize.
This simple circuit -and its partner below- may be more useful than you realize.
maximum.gif (5.45 KiB) Viewed 287 times
minimum.gif
minimum.gif (5.31 KiB) Viewed 287 times
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Re: Recommendations for a complete DIY rack

Post by KSS » Thu Jun 10, 2021 10:58 pm

Pr0fBi0 wrote:
Thu Jun 10, 2021 10:35 pm
KSS wrote:
Thu May 20, 2021 11:46 pm
Go with 6U,104HP.

Build the AI, and add a couple of their mixers too. <--Or somebody else's but have some mixers on hand.

Make sure you've got some sort of bias-offset utilities, or wire DC into the normal of at least one mixer channel per mixer. Wiring -5V into one channel and 5V+ into a second lets you cover a lot of territory a mixer and system without these will miss..
I was going back and re-reading the early posts and I can see now I had no idea what this meant at the time. It's like you were telling me I needed to know how to play arpeggios but I didn't know what a chord was yet.

I can see how useful it would be now. How would you know how much you are offsetting by? Do you have to have an oscilloscope to be precise? I'm going to have to research how to normalize something but have it change when a cable is plugged in. And also how to get the +5v and -5v wired into the channels.
Your ears are the best synthesis tools. You will know how much offset by the result in the sound. You definitely do NOT need an oscilloscope to build or use synths. That doesn't mean they aren't sometimes helpful. And with some few modules, necessary. But don't fall for the you need gear trap! Thousands of synths have been made and used with little more than a basic volt-ohmmeter or DMM.

Working through some of the Doepfer DIY examples will help.

We use mostly mono jacks in synths. They often have thrre connections. One is the tip which receives or sends the signal or voltage. <--Which are really the same thing.
The second is the sleeve which has traditionally been called ground but which is better referred to as 0V or signal ground. It's the reference for the signal voltage. Because voltage is always in reference to something. Voltage is the push, current is the flow itself.
The third contact of the typical jack is the 'normal' or switch. It feeds into the tip contact until a plug is inserted into the jack. If you connect -5V or 5V+ to this switch-normal contact, it will feed whatever the tip contact is wired to. Until a patchcord plug is inserted. Then the plug tip will feed the circuit connnected to that tip contact or the circuit connected to that tip contact will feed the plug tip. The 5V you attached just sits idly by unconnected to anything while a plug is in the jack.
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Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Thu Jun 10, 2021 11:09 pm

Sounds similar to how a 9volt battery harness works on the input jack of guitar pedal, but instead of only being on when it's plugged in, it's opposite. I was a little curious as to why the jacks had 3 pins.

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Re: Recommendations for a complete DIY rack

Post by KSS » Thu Jun 10, 2021 11:13 pm

I thnk I remember you wanted to add an S/H module?
Here's a really good S/H module I bet you could wire up.
It would be a good candidate for an early try at laying out a stripboard, wiring on pad-per-hole or breadboards style PCBs, or even designing a PCB with Diptrace or KiCAD.

Edit: You can also see how it normals the clock made from 1/4 of the 4093 into the trig jack.

As long as the 398's are available it makes little sense to use older -and usually more expensive- individual FETs to do the S/H function.

You can break this circuit down into its functional section fairly easily. There's a clock, a trigger input which is conditioned by 3/4 of the 4093 to become an effective and short 3uS sampling pulse for the 398 S/H chip.

As a mod, think about how you'd add a track and hold vs. sample and hold switch. I've left a clue in italics above. Having track and hild is very useful and a good thing in an S/H module. Even if you can;t figure it out now, layout the panel with it in mind. So you can add it later when you know how. <--This is a powerful approach to diy too.

One thing i left out of the last few posts is the value of reading component datasheets. The 398 is a good example of a helpful datasheet. Here it can nelp you determine what -if anything- needs done to take this circuit from the 15V shown to the 12V of EuroRack.
Attachments
yash.png
yash.png (9.64 KiB) Viewed 274 times
Last edited by KSS on Thu Jun 10, 2021 11:29 pm, edited 3 times in total.
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Re: Recommendations for a complete DIY rack

Post by KSS » Thu Jun 10, 2021 11:17 pm

Pr0fBi0 wrote:
Thu Jun 10, 2021 11:09 pm
Sounds similar to how a 9volt battery harness works on the input jack of guitar pedal, but instead of only being on when it's plugged in, it's opposite. I was a little curious as to why the jacks had 3 pins.
Yes. If you look closely at your jacks as you plug in a patchcord you can see it in action.

Stereo TRS plug may have normals or switches on both Tip and Ring. This is how they go from speakers to headphones when you insert the plug.

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Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Fri Jun 11, 2021 12:38 am

i think you have convinced me to try that as my first diy from scratch build. but i have a few questions.

1.) What does the weird diagonal arrow over the 1meg resistor mean? never seen that before.
2.) is the 2.2k resistor the one that controls the LED brightness?
3.) what perfboard/veroboard/protoboard do you recommend? and how do you mount it to the faceplate?

also that 1n (styrene) labeling had me very confused for a bit. I kept reading it as in instead of 1n. :hihi:

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Re: Recommendations for a complete DIY rack

Post by KSS » Fri Jun 11, 2021 2:05 am

Pr0fBi0 wrote:
Fri Jun 11, 2021 12:38 am
i think you have convinced me to try that as my first diy from scratch build. but i have a few questions.

1.) What does the weird diagonal arrow over the 1meg resistor mean? never seen that before.
2.) is the 2.2k resistor the one that controls the LED brightness?
3.) what perfboard/veroboard/protoboard do you recommend? and how do you mount it to the faceplate?

also that 1n (styrene) labeling had me very confused for a bit. I kept reading it as in instead of 1n. :hihi:
1- It's a variable resistor aka pot. Normally the arrow stops at the wigglies. Sometimes you'll see them without the arrow connected at all. It's still the same as seen here. The 4093 is being used an oscillator. If you read seamoss.com or Nic Collins Handmade Music book you'll see this. Also the Lunetta forum at Electro-music in the DIY section has many circuits like this clock.

2- Yes.

3. Yes. Any will work, it's kind of up to what you feel most comfortable with. To find that out you have to try them out. If the Nicolas Woollaston ADSR drawing made sense, I'd go with vero or strip board. If you're used to using a breadboard aka white plastic thing with hundreds of holes in long lines, then using a PCB that is set up the same way will be easier than the stripboard. One well-known DIY guy uses pad per hole and says he just starts in one corner and goes from there. Pad per hole means you have to wire everything. It's more flexible but more work too. I'd use one of the first two.

The three most common ways to -traditionally- mount a DIY PCB are
- using the pots or switches which are soldered into the pcb as the mounting. Typically you'd want at least two for that but with a small circuit one can be enough.
- Using little right angled L-bracket pieces sold and meant for this use. Read an old PAIA manual -or just look up some of their module photos to see these. You can also make your own L-brackets with metal, plastic or 3D printing. Thingiverse.com will have examples.
- Using a large bent sheet metal bracket -you can buy already bent as roofing flashing at a place like Home depot. Google stooge brackets and MOTM modules to see these. The Musicfromouterspace.com site also shows module assembly methods using this kind of bracket. MW member Dr Sketch-n-Etch has photos in his thread of this type too.

You already know a fourth way from the kits you've built. Parallel PCB using the panel parts -pots, switches to hold it to the panel. This has become the new standard because it is cost efficient and makes a solid build. But it can also restrict PCB size, and requires specific components so everything lines up right. Depending how it's used it can also enforce strict layouts with little room or ability to modify and add to.

One thing not seen too often -outside the example I'm about to give- which can also work well is a parallel PCB mounted using three or four LONG standoffs and then wiring the panel parts to the PCB. This can be the best of both worlds. See the synthesizers.com site for examples of how this looks and works. Or look up Dotcom module photos which is the same thing. They use connectors for everything but you don;thave to. Just be sure your wires are long enough or arranged so that the PCB can be 'folded' so that you can get to both sides for service. Classic Serge format panels show thid folding technique and also another way to mount PCBs parallel to the panel and wiring from PCB to panel parts.

It's always a good idea to think about how you will service something you make. Small choices now can save much time later. But don't worry too much about a rats nest of wires either. Most synth circuits are pretty forgiving. With that said, be sure to read the 398 datasheet before you plan your layout. The things attached to pin 8 are the -potential- big issues here.

I'm sure there are layouts online for the YASH. Even if you don't use them, it can be useful to see how others have solved problems you're facing. Again Electro-music's DIY section is excellent as a resource. There is a sticky there with many tested layouts for all kinds of modules.

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Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Fri Jun 11, 2021 10:29 am

KSS wrote:
Thu Jun 10, 2021 10:40 pm
*min max schematic*
this is really good! I like this one way more than the serge transistor min max. I see it even compensates for the voltage drop of one diode on the NPN BE junction by having an equal opposite voltage drop in the other direction on the PNP output buffer. current consumption is limited by two 4K7 resistors.

minmax.pdf
(18.69 KiB) Downloaded 12 times
I was digging for the opamp min max schematic but I could not find the one I remember. so I remixed the tellun schematic without the threshold control. without the switch. here is a method to do it with opamps. tellun has a low pass on the output but also there is a cable capacitance compensation driver. you can probably delete all that stuff to reduce parts count and reduce slew. let me know if there are any mistakes.
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Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Fri Jun 11, 2021 10:45 am

Pr0fBi0 wrote:
Fri Jun 11, 2021 12:38 am
3.) what perfboard/veroboard/protoboard do you recommend? and how do you mount it to the faceplate?
tayda template.pdf
(19.44 KiB) Downloaded 3 times
use this PDF print out to draw your circuits with pencil. you can erase any mistakes or use a fresh sheet of paper.
you can buy the boards here for $0.66
https://www.taydaelectronics.com/small- ... opper.html

you will need a razor knife or a drill bit to cut the copper traces in some places where you do not want two things connected. I use this.


however you will need to buy a 1/8 inch bit because the shape of the tip of the 3mm bit provided with the kit is not what you need.
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Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Fri Jun 11, 2021 1:54 pm

had some random thoughts going through my head and i may have a super dumb question

would a 3 channel attenuverter be the same circuit as a 3 channel mixer, but instead of combining the signals they just have their own individual outs? If so does that mean you can use just a single channel in a cv mixer as an attenuator?

*nevermind* just tried it out on my lunch since i'm working from home and it works just like i thought!

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Re: Recommendations for a complete DIY rack

Post by KSS » Fri Jun 11, 2021 3:04 pm

Yes, glad you worked it out.

Two issues come up with attenuverters. First is that the range from 0 to - or 0 to + is now only half the knob travel. It's harder to set a precise value than with a full range knob.

Second, the ability to get back to zero can be hard. Adding back to back diodes is how traditional synths handled this one for their pitch bend knobs. Look at any ARP service manual for a keyboard synth to see examples of this circuit.

There are different solutions for these issues. One is to use a switch to invert -or not- the attenuation. This works well but you have lost the attenuverter's ability to easily transit zero as you go from one polarity to the other. And you have the added expense and panel space required for the switch. A push-push pot or a push pull type can embed the switch in the pot's footprint and not require any additional panel space.

A second often proposed solution to the zeroing problem is to use a pot with a center detent. I don't care for this one because it means you can't get any pot setting near zero since at that point in the rotatation -or travel is using a slider pot- the pot drops into the detent.

Having an attenuverter is a very useful addition to many modules and as a separate function utility module too. Think about these different choices as one may be better than another dpending on the actual expected use.

-------------------
If you do make an attenuverter utility module, it's nice to include a bipolar LED display to show what the signal is doing. Color blind people will appreciate having two LEDs instead, one showing positive and the other showing negative.

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Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Fri Jun 11, 2021 3:54 pm

I agree with KSS. attenuverters make it hard to get a perfect 0v. this is why I have no attenuverters in my rack. I have flying attenuators on cables to save space in the rack. I have a 2HP module that inverts 3 signals. it includes unity gain mixers but I don't use that feature. I could have definitely done this in DIY but it would not be 2HP.

https://malekkoheavyindustry.com/product/invert-mix/
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Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Fri Jun 11, 2021 4:19 pm

i was toying with the idea of having a 3-4 channel cv mixer, where the first 2 inputs could be normalized to +5volts and -5Volts, and then have an individual output for each channel that is normalized to mix, but then seperates to an individual out if something is plugged in. Then you could offset, mix, offset and mix, or isolate and attenuvert...but i may be shooting for the moon. need to get back to earth and build the Yash first.

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Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Fri Jun 11, 2021 5:26 pm

Pr0fBi0 wrote:
Fri Jun 11, 2021 4:19 pm
i was toying with the idea of having a 3-4 channel cv mixer, where the first 2 inputs could be normalized to +5volts and -5Volts, and then have an individual output for each channel that is normalized to mix, but then seperates to an individual out if something is plugged in. Then you could offset, mix, offset and mix, or isolate and attenuvert...but i may be shooting for the moon. need to get back to earth and build the Yash first.
I made this for you. the output is inverted. the individual outs are not inverted.
custom_mixer_1a.pdf
(18.79 KiB) Downloaded 5 times
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Re: Recommendations for a complete DIY rack

Post by KSS » Fri Jun 11, 2021 5:32 pm

Pr0fBi0 wrote:
Fri Jun 11, 2021 4:19 pm
i was toying with the idea of having a 3-4 channel cv mixer, where the first 2 inputs could be normalized to +5volts and -5Volts, and then have an individual output for each channel that is normalized to mix, but then seperates to an individual out if something is plugged in. Then you could offset, mix, offset and mix, or isolate and attenuvert...
:tu:

Edit: Sounds a little bit like half of this. In this 50SQ format the ten positions upper and lower go to jacks or a more elaborate matrix switching system. It's nice to be able to move an input to either the mix up or mix down mixer at will. Muting comes along for the ride in the middle toggle position. Toggles here are represented by black filled rings. The expanders just allow different type jacks to access the main 1008 unit. Since bananas can't normal like other jacks the toggles there let you do it manually.
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APT-50SQ-1008-2c-CLR.jpg
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Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Fri Jun 11, 2021 7:03 pm

EATyourGUITAR wrote:
Fri Jun 11, 2021 5:26 pm
Pr0fBi0 wrote:
Fri Jun 11, 2021 4:19 pm
i was toying with the idea of having a 3-4 channel cv mixer, where the first 2 inputs could be normalized to +5volts and -5Volts, and then have an individual output for each channel that is normalized to mix, but then seperates to an individual out if something is plugged in. Then you could offset, mix, offset and mix, or isolate and attenuvert...but i may be shooting for the moon. need to get back to earth and build the Yash first.
I made this for you. the output is inverted. the individual outs are not inverted.
custom_mixer_1a.pdf
oh that is awesome! if i'm understanding the schematic right the upper left is the power header and power filtering or conditioning(not sure which applies). and the 444 and 888 there means you connect those to pins 4 and 8 of the 3 ICs? And the v- i'm assuming is your negative voltage rail, and if there was anything using negative voltage it would connect to this?

the upper right is using half an IC to convert the 12 volt positive to both positive and negative 5 volts for the offsets. didn't know you could do that with a simple op amp.

the 4 channels seem easy enough to understand. I like how the jack icon is shown, you can imagine a cable going in and pushing it away from pin 2. The "normalized" i keep reading about and you guys explained makes sense now.

is there a reason the mix jack at the end isn't normaled to ground?

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Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Fri Jun 11, 2021 7:17 pm

Everything you said is correct.
V+ is +12V
V- is -12V
GND is 0V

Outputs do not get normals to ground. There is no benefit. Only a undesirable affect of increased current consumption. It is extremely rare but you may find a midi to CV converter output with an expensive opamp that can not survive shorts to ground through a low value resistor such as a 33R. In that situation, the reason opamp outputs have the output resistor so small is to reduce the voltage sag that could send a VCO out of tune. You see it on a precision adder, quantizer, buffered multiple, tuning modules or precision Voltage reference modules. Most other modules have a 1K resistor between the opamp output and the output jack tip. There are also stories about electro static discharge (ESD) aka getting shocked from static electricity. Having an unprotected opamp is a $0.50 part failure waiting to happen. Some opamps are $7 but these are the ones that get the low value resistor and have weird specifications. They might be the most vulnerable to user error or interesting design trade off.
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Re: Recommendations for a complete DIY rack

Post by Kawouddd » Sat Jun 12, 2021 3:01 am

*redundant post! Replied to a post before revisiting the op.

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Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Sun Jun 13, 2021 3:56 pm

viewtopic.php?f=17&t=244412&sid=4d5d103 ... b4d530ebe9

I was running into some issues with this SMD transistor filter build. basically getting nothing from it. the troubleshooting instructions mention to focus on the input section of the bild which from what i can tell looks good. but it does go through parts of the TL074 ICs 3 times before getting to the clipping LED when he mentions as the way to see if your input is making it into the circuit. My clipping LED doesn't light up at all. I'm wondering if i put the TL074s in backwards.

These are the ICs i bought: https://www.mouser.com/ProductDetail/511-TL074CDT. there's no real visual indication of pin 1, and the datasheet shows a dot next to pin one, but i'm not seeing anything like that indicating pin one on the chip. Without any real indication of which pin was pin one i just defaulted to pin one being the bottom left if the text was right side up.
PXL_20210613_201631931.jpg
it was also super hard to identify the anode and cathode of the diodes. i put my meter into continuity mode (which has the diode icon on it too) and checked each one before placing it that i got a reading with the black lead on one side but not the other. the side you get the reading on is then the cathode (side with the line) so I'm pretty sure i got my diodes in correctly. no shorts between +12 , -12, and ground. no odd behavior from other modules when it's hooked up and powered up, just no signs of life.


i did have some suspect soldering connections that i fixed and cleaned excess flux off the board but that didn't change the behavior at all. hoping i didn't fry an IC or solder in any backwards. it doesn't seem like it would be possible to unsolder them without getting a hot air reflow station.

(also why does my inline attached picture show rotated, but when you click the picture it's upright?)


****Edit***
Did a bunch of Google searches and finally found someone with a similar problem and the package outline held the key. Apparently the smd chip has a champfer on the edge that pin 1 is on. After checking all my ICs are in correctly. Gonna have to keep trouble shooting.

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Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Sun Jun 13, 2021 9:43 pm

well i feel dumb/not dumb. apparently i had the LEDs in backwards. I was under the assumption that the square pad was positive/longer pin on LEDs but after following the schematic and testing continuity i wasn't getting continuity where i expected on the LEDs. on this one the square pad is the negative. flipped all the LEDs and now i have sound. there's a few other parts not working, but now i have something to work with!

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EATyourGUITAR
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Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Sun Jun 13, 2021 11:15 pm

square pad always negative for caps or LED's. for pin headers with one square pin that is pin 1 or sometimes the pin that carries ground.
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Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Sun Jun 13, 2021 11:54 pm

I wonder if some pcb designers don't know or follow this rule. Most of the pedals I've built are from rullywow, and they clearly put the square pad on the + side of caps and LEDs, but on the - side of diodes. But other pcb makers have it the other way. Makes me really appreciate it when they print the actual polarity on the board, or print the led circle with the flat side on the board.

Another thing I'm going to have to be careful of on future builds.

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KSS
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Re: Recommendations for a complete DIY rack

Post by KSS » Mon Jun 14, 2021 12:45 am

Both versions of square pad ident are found for diodes and LEDS in more than just synths. You ALWAYS need to check -and verify- to see what the PCB designer did.

Edit: I personally favor the square pad for cathode to represent the also 'square' line of its schematic symbol.

ARP always used two rounds and let the assy drawing show by where the vertically installed body was drawn. It was understood that the body was always installed in that position with the band end down towards the PCB. In some clones of those submodule PCBs -which had no silkscreen- they put a circle around the pad with the body and so ident the cathode due to band side down.

You always need to check. Always.

I'd say it's even more important now with so many 'commercial' designs put out by rank beginners due to the ease and low cost -aka free- of using ECAD. Some really crappy schematics and layouts out there now.
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Re: Recommendations for a complete DIY rack

Post by AlanP » Mon Jun 14, 2021 3:00 am

Pr0fBi0 wrote:
Wed Jun 09, 2021 3:36 pm
I also find it funny that in the guitar pedal world everyone also sockets transistors, but in all of the module builds I've done nobody has said anything about sockets for transistors. And as far as I've seen I haven't killed one with heat yet.
Stompboxes abuse transistors for deliberate distortion, and different types of transistor distort differently. If you're using germanium transistors, then different transistors of the same type distort differently. So being able to audition various transistors in a circuit without soldering/desoldering is a definite bonus. Different reason entirely for socketing.

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Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Mon Jun 14, 2021 11:13 am

AlanP wrote:
Mon Jun 14, 2021 3:00 am
Stompboxes abuse transistors for deliberate distortion, and different types of transistor distort differently. If you're using germanium transistors, then different transistors of the same type distort differently. So being able to audition various transistors in a circuit without soldering/desoldering is a definite bonus. Different reason entirely for socketing.
apparently germaniums even change how they distort with heat. I can see socketing in a fuzz, but i've also built a chorus, tremolo and compressor pedal where they suggest using sockets on transistors. I would imagine in those circuits they are mainly using the transistors to amplify and thus swapping parts wouldn't change much. But i did start socketing diodes in overdrive pedals. i was kinda shocked at how different diodes could completely change what overtones were distorted and change the feel of the pedal. I initially tried 1n4148 in my king of tone clone and hated it. bought some MA858 diodes and it completely changed the tone and made it warmer. but I think in any new pedals i build I'm going to just solder in the transistor if it's not part of a clipping section. beats having to make the legs wavy to try and get them to stay in sockets.
KSS wrote:
Mon Jun 14, 2021 12:45 am
You always need to check. Always.
Yeah, this was a good lesson for me I think. I see now that the panel has two lines drawn between the pads on the top and the bottom. i didn't think anything of it and the lines stop at the pads. but if you were to continue the lines to go around the outside of the pads it would have been round on the circle side and straight on the square side. which matches the flat (negative) side of the led. I didn't see it this way before but i can see now that it's probably what he intended when designing the screenprint for the PCB.

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