Help with substituting through hole with SMD

[MidnightArrakis]

I have a "misunderstanding/question" about the DC-voltage input coming into this circuit of yours. Here is an image of the DC-in of your original schematic:



Up at the top, you can see both a "9V" and a "+9V" symbols. So, I am assuming that the "9V" is the main DC-input from a wall-wart or something. But, does it also connect to the connection line going from R4 and C2 and the "+9V" symbol? Or, does it - ONLY - connect to D7? And, if so.....where does the voltage go from there as D7 only connects directly to GND? In addition, technically..... the anode of D7 won't connect to the rest of the circuit because it has its own NET NAME called "9VGND", whereas the rest of the circuit all has a NET NAME called "GND". So, within a CAD-system, the NET NAME called "9VGND" would be what is called a "Single Node Net" and would -- NOT -- be connected to anything else in the circuit. Should "9VGND" be changed to "GND" as well?

Here is the same "input" section of your schematic, but it shows things differently:

Since there is no "+9V" symbol shown in this version, I can only assume that the "9V" symbol shown is the main DC-input voltage. If that is true, then shouldn't there be a "connection dot" shown on the connection line going from R14 to D7 to C10 and the "9V" DC-input symbol? That's the only scenario that makes sense to me!!! But, I am not a circuit designer, so maybe this is shown to be correct, anyhow. Let me know, OK?

It is probably a "good thing" that you are converting the "Thru-Hole" components over to "Surface-Mount" types because when I did a check of the - IRF740 - device on Digi-Key, there was a message displayed mentioning that this part is now - OBSOLETE - and is no longer manufactured. Of course, that doesn't mean that you cannot still buy it from existing inventories, but the device itself has seen its "End Of Life" notice.

What is the difference between switching to D1 and D2 or D3 and D4 by the "Diode Clip" switch? It appears as though that both pairs of diodes are the same, so what is being differently switched? And, what types of diodes are they? 1N4148's? Also, how is that switch an "On/Off/On" switch when it is only switching between two poles or an "either/or" condition? That would be an "On/On" switch, wouldn't it? And, finally.....the "Diode Clip", "High Cut" and "Bright" switches do not have any "Reference Designators" shown within the schematic? Is there a reason for this?

I am assuming that SW2.1 and SW2.3 are a part of the same switch, right? Is there a SW2.2 somewhere that I am not seeing? And, the connection between SW2.3/C3 and SW2.1/A1 is a "BYPASS" setting, correct?

I am guessing that the potentiometer called "V-ADJ" is a trim-pot, right? And, it is used to fine-tune the voltage? Single-turn? Or, a 3-turn trim-pot?

It appears as though the Surface-Mount version of the "Thru-Hole" J201 FET (MMBFJ201) is back-ordered/non-inventoried/out-of-stock at all of the normal and usual electronics distributors, but I was able to find one distributor here in the U.S. who has 10,786-pieces in-stock in their warehouse. I just thought that you would like to know this tidbit of information.

Are you planning on building this circuit using the HAMMOND 1590BB enclosure as a "Stomp-Box"? Or, as a type of an external "Effects Box" device? The difference would determine what types of switches should be specified for the various functions.

Going back to the "Power Supply".....what do you have planned for the main "9VDC" input? A wall-wart? An external power supply or what? Would you consider operating this enclosure off of your "AC Mains" (85 - 305VAC) voltage if you knew of an AC/DC converter that could supply you with your 9VDC @ 5Watts that's about the size of a large postage stamp and is only 20mm high? Would 12VDC be OK?

Would you want to have "F1" accessible for changing from -- OUTSIDE -- the enclosure? Or, would you prefer to remove the lid and change out the fuse from a PCB fuse-holder? Inquiring minds need to know!!!

Well.....that's enough for now.....

/

 

[sonolink]

I'll try to answer the best I can ok?

I have a "misunderstanding/question" about the DC-voltage input coming into this circuit of yours. Here is an image of the DC-in of your original schematic:

View attachment 99290

Up at the top, you can see both a "9V" and a "+9V" symbols. So, I am assuming that the "9V" is the main DC-input from a wall-wart or something. But, does it also connect to the connection line going from R4 and C2 and the "+9V" symbol? Or, does it - ONLY - connect to D7? And, if so.....where does the voltage go from there as D7 only connects directly to GND? In addition, technically..... the anode of D7 won't connect to the rest of the circuit because it has its own NET NAME called "9VGND", whereas the rest of the circuit all has a NET NAME called "GND". So, within a CAD-system, the NET NAME called "9VGND" would be what is called a "Single Node Net" and would -- NOT -- be connected to anything else in the circuit. Should "9VGND" be changed to "GND" as well?

Here is the same "input" section of your schematic, but it shows things differently:
View attachment 99293
Since there is no "+9V" symbol shown in this version, I can only assume that the "9V" symbol shown is the main DC-input voltage. If that is true, then shouldn't there be a "connection dot" shown on the connection line going from R14 to D7 to C10 and the "9V" DC-input symbol? That's the only scenario that makes sense to me!!! But, I am not a circuit designer, so maybe this is shown to be correct, anyhow. Let me know, OK?

The PSU circuit is not mine and I have checked and you are right, there should be a dot there. I have corrected it now but the weird thing is that when hovering over the net with my mouse in Diptrace it highlights the net correctly....anyway thanks for pointing that out

It is probably a "good thing" that you are converting the "Thru-Hole" components over to "Surface-Mount" types because when I did a check of the - IRF740 - device on Digi-Key, there was a message displayed mentioning that this part is now - OBSOLETE - and is no longer manufactured. Of course, that doesn't mean that you cannot still buy it from existing inventories, but the device itself has seen its "End Of Life" notice.

I'm doing it mainly to be able to fit everything inside the enclosure I have chosen.

What is the difference between switching to D1 and D2 or D3 and D4 by the "Diode Clip" switch? It appears as though that both pairs of diodes are the same, so what is being differently switched? And, what types of diodes are they? 1N4148's? Also, how is that switch an "On/Off/On" switch when it is only switching between two poles or an "either/or" condition? That would be an "On/On" switch, wouldn't it? And, finally.....the "Diode Clip", "High Cut" and "Bright" switches do not have any "Reference Designators" shown within the schematic? Is there a reason for this?

The diodes are the same on the schemo because one can use different ones depending on the kind of clipping one wants. I will probably use 4148s and LEDs but I haven't decided yet. That's why I kept those TH to be able to socket them and try out different ones.

The reason it's an On/Off/On switch is because the original Fender circuit didn't have the diodes. I added these because the original circuit is a preamp designed to work with a tube power amp. This way, one can choose to use the pedal as a preamp in front of a power amp, as a tube preamp pedal in front of a guitar amp, as a tube distortion/overdrive pedal, or as a combination of all.
So, basically the Off position of the switch would be "No diodes".

The hidden RefDes are just a personal choice, that's all.

I am assuming that SW2.1 and SW2.3 are a part of the same switch, right?

Correct

Is there a SW2.2 somewhere that I am not seeing?

Yes, SW2 is a 3PDT footswitch. The part not shown are the poles reserved for LEDs to show the state of the switch.

And, the connection between SW2.3/C3 and SW2.1/A1 is a "BYPASS" setting, correct?

Correct. Basically it's the On-Off Switch to engage the effect.

I am guessing that the potentiometer called "V-ADJ" is a trim-pot, right? And, it is used to fine-tune the voltage? Single-turn? Or, a 3-turn trim-pot?

Correct. Single turn.

It appears as though the Surface-Mount version of the "Thru-Hole" J201 FET (MMBFJ201) is back-ordered/non-inventoried/out-of-stock at all of the normal and usual electronics distributors, but I was able to find one distributor here in the U.S. who has 10,786-pieces in-stock in their warehouse. I just thought that you would like to know this tidbit of information.

There are other substitutes also for the J201. That part of the circuit is a Cab Simulator. The original is called Simple CabSim v.2, by Lart. The thing is that I have changed that part of the circuit and I'm using Merlin's CabSim so I don't need J201 no more.

Are you planning on building this circuit using the HAMMOND 1590BB enclosure as a "Stomp-Box"? Or, as a type of an external "Effects Box" device? The difference would determine what types of switches should be specified for the various functions.

As a stompbox

Going back to the "Power Supply".....what do you have planned for the main "9VDC" input? A wall-wart? An external power supply or what?

My idea was to use a Truetone One Spot 9v/2A wall wart. It's clean and reliable and many guitar players have one.

Would you consider operating this enclosure off of your "AC Mains" (85 - 305VAC) voltage if you knew of an AC/DC converter that could supply you with your 9VDC @ 5Watts that's about the size of a large postage stamp and is only 20mm high? Would 12VDC be OK?

I would definately give it a thought! I guess 12v would be ok too. The pedal needs about 2A or close to work. I'd have to check if the Mosfet would handle that properly and if the PSU would remain stable outputting 250V

Would you want to have "F1" accessible for changing from -- OUTSIDE -- the enclosure? Or, would you prefer to remove the lid and change out the fuse from a PCB fuse-holder? Inquiring minds need to know!!!

I was planning to use a self resetting fuse like a polyswitch for F1

Well.....that's enough for now.....

You are very welcome to ask. And if you want the files of the schemos, etc, I'd be glad to share

Cheers
Sono

 

[MidnightArrakis]

Have you ever considered something like "THIS" for your stomp-box enclosure? Makes more sense to me for "stomping"!!!

 

[sonolink]

Have you ever considered something like "THIS" for your stomp-box enclosure? Makes more sense to me for "stomping"!!!

View attachment 99310

Thanks for the suggestion, but.....mmm......naaaaaaah.....no way
Guitar pedals are not about "making sense"!

Also:
-That enclosure has less space and the space covers an odd geometric figure. Not a rectangle (which is way easier to handle when doing a layout). No way to fit a tube in there.

-That "trapeze" look (to my eyes) looks simply awful

-Pedals should ALWAYS be rectangles (or SOMEtimes circles, but to look vintage hahaha).
My point of view, of course

Just MY point of view of course

Cheers
Sono

 

[MidnightArrakis]

I'll try to answer the best I can ok?


The PSU circuit is not mine and I have checked and you are right, there should be a dot there. I have corrected it now but the weird thing is that when hovering over the net with my mouse in Diptrace it highlights the net correctly....anyway thanks for pointing that out





I'm doing it mainly to be able to fit everything inside the enclosure I have chosen.




The diodes are the same on the schemo because one can use different ones depending on the kind of clipping one wants. I will probably use 4148s and LEDs but I haven't decided yet. That's why I kept those TH to be able to socket them and try out different ones.

The reason it's an On/Off/On switch is because the original Fender circuit didn't have the diodes. I added these because the original circuit is a preamp designed to work with a tube power amp. This way, one can choose to use the pedal as a preamp in front of a power amp, as a tube preamp pedal in front of a guitar amp, as a tube distortion/overdrive pedal, or as a combination of all.
So, basically the Off position of the switch would be "No diodes".

The hidden RefDes are just a personal choice, that's all.




Correct



Yes, SW2 is a 3PDT footswitch. The part not shown are the poles reserved for LEDs to show the state of the switch.



Correct. Basically it's the On-Off Switch to engage the effect.



Correct. Single turn.




There are other substitutes also for the J201. That part of the circuit is a Cab Simulator. The original is called Simple CabSim v.2, by Lart. The thing is that I have changed that part of the circuit and I'm using Merlin's CabSim so I don't need J201 no more.


As a stompbox



My idea was to use a Truetone One Spot 9v/2A wall wart. It's clean and reliable and many guitar players have one.




I would definately give it a thought! I guess 12v would be ok too. The pedal needs about 2A or close to work. I'd have to check if the Mosfet would handle that properly and if the PSU would remain stable outputting 250V




I was planning to use a self resetting fuse like a polyswitch for F1



You are very welcome to ask. And if you want the files of the schemos, etc, I'd be glad to share

Cheers
Sono

[it's an On/Off/On switch] -- Can you supply me with a Part Number of the switch you are planning on using?

[SW2 is a 3PDT footswitch] -- Part Number?

[The part not shown are the poles reserved for LEDs] -- Can you update your schematic to show how both this switch and the LEDs are connected into the circuit?

[I don't need J201 no more] -- (any more) -- Can you update your schematic to show what it is that you are doing now?

[a Truetone One Spot 9v/2A wall wart. It's clean and reliable and many guitar players have one] -- GOT IT!!! 9VDC @ 2.0A, using the formula P = I X E, means that your wall-wart can supply 18-Watts. I'll check my resources and see what other types of miniature power-supplies are available. These are really cool items!!! I have bought a bunch of them for my personal projects.

[I'd have to check if the MOSFET would handle that properly and if the PSU would remain stable outputting 250V] -- Interested!!!

[planning to use a self resetting fuse like a polyswitch for F1] -- Not my first choice to use, but to each their own.
[if you want the files of the schemos, etc., I'd be glad to share] -- GREAT!!! Just make any and all updates to the schematic first so it reflects your latest version of what it is that you are planning on having this circuit do for you. What software is your schematic drawn with? Some programs I can directly import, while others I have to come up with some kind of work-around.

> Speaking of CAD-software, when I downloaded my version of the KiCAD software, I also went ahead and paid for their training course which consists of about 8.5GB of bite-sized video files which very carefully details every aspect of using the program. It cost me all of a whopping USD $40 (EUR 41.07) and it was well worth it in order to overcome the learning curve. Here is the link to another KiCAD training site for you:

https://circuitstate.com/tutorials/...ginners-tutorial-to-schematic-and-pcb-design/
[That enclosure has less space] -- Overall Dimension: 81mm x 60mm x 150mm Depth

[the space covers an odd geometric figure] -- Perhaps "odd", but certainly still "workable"!!! I could easily package your electronics into this enclosure!!! NO BIG DEAL!!! (See attached PDF file).

[That "trapeze" look (to my eyes) looks simply awful] -- Again.....to each their own. But.....many, many early fuzz-boxes and other early guitar effects boxes were of this shape because they made it easier for the guitarist to see where the switches were located and stomp on them. Most, if not all, of the "WAH-WAH" pedals back in the 60's and 70's were made in angled or sloped enclosures. They just made "sense"!!!

I have again included some PDF files for your perusal. I am guessing that 2 of them you will gag on and the other you will probably say to yourself "WTF"!!! It's a photograph of one of my "Electronics Packaging" projects.

/

 

[sonolink]

[it's an On/Off/On switch] -- Can you supply me with a Part Number of the switch you are planning on using?

Just the usual toggle switch you can find on any stompbox, like this one:
https://stompboxparts.com/switches/dpdt-toggle-switch-on-off-on-pcb-pin-short-bat/

[SW2 is a 3PDT footswitch] -- Part Number?

Same as above: 3PDT Footswitch PRO - PCB Pin

[The part not shown are the poles reserved for LEDs] -- Can you update your schematic to show how both this switch and the LEDs are connected into the circuit?

I usually never draw that part, and just add it when laying out because it's dead simple. Just feed one side of the footswitch with 9v so that when switched on it feeds the LED's resistor.

[I don't need J201 no more] -- (any more) -- Can you update your schematic to show what it is that you are doing now?

This is my last schemo:
https://ibb.co/ggvx093

What software is your schematic drawn with? Some programs I can directly import, while others I have to come up with some kind of work-around.

Diptrace


Cheers
Sono

 

[MidnightArrakis]

Just the usual toggle switch you can find on any stompbox, like this one:
https://stompboxparts.com/switches/dpdt-toggle-switch-on-off-on-pcb-pin-short-bat/


Same as above: 3PDT Footswitch PRO - PCB Pin




I usually never draw that part, and just add it when laying out because it's dead simple. Just feed one side of the footswitch with 9v so that when switched on it feeds the LED's resistor.




This is my last schemo:
https://ibb.co/ggvx093


Diptrace


Cheers
Sono

[Just the usual toggle switch you can find on any stompbox] -- I guess that the switches used on today's stompboxes must have changed considerably since the stompboxes I saw and worked on during the 60's and 70's. Back then, the switches were of a type far more heavy-duty than the ones you have shown. The switches used back then were more of an industrial-grade type. WOW!!!

[I usually never draw that part, and just add it when laying out because it's dead simple] -- Hmmmmmmmm.....While you are certainly free to design, build and operate in any manner that you wish to do so.....what you are doing is "not how things are done".....normally.

While I do admit that my background with building electronic equipment is different than yours, one of the purposes of having a schematic is to have and to show what your circuit is -- WITHOUT -- needing to have anyone else perform "mental gymnastics" of filling-in the blanks of what your schematic is -- NOT -- showing!!! And.....I could certainly be wrong here, but.....I believe most all of the other members of this forum would agree that sharing an incomplete schematic really doesn't do anyone else any good.

[Just feed one side of the footswitch with 9v so that when switched on it feeds the LED's resistor] -- OK.....so that just might be super simple, but.....now imagine if 10 other members of this forum asked you the same question as I did. You would have to reply to each of those 10 other members with the same answer!!! If you had just simply added that small part of the circuit into your schematic, then that question is automatically answered. But, you go ahead and do things the way that you want to. That's your prerogative. Who am I to tell someone else how to design their schematics. I just follow industry-standard "best practices and guidelines" and that seems to work well enough for me. But, what do I know???

[This is my last schemo] -- I get the feeling that there isn't going to be any further "positive movement" here on your project, so I am merely going to drop-out. In assuming that you have viewed my project PDF file I sent in my previous message, I am guessing that you could maybe glean a bit of what I am capable of doing for you and I was more than willing to help you out in designing and building your stompbox project. But, you have your own personal ways of doing things.....which you are certainly free to have!!!.....and some of those methods run quite contrary to how I have worked designing electronic equipment for various aerospace companies, defense contractors, medical electronics firms, NASA, R&D laboratories and other types of electronics companies. So, I think it is best that you design, develop and build your stompbox in the manner that you are most comfortable with doing, without you having to learn and/or meet any form of accepted electronics industry practices or standards.

GOOD LUCK!!!

/

 

[MidnightArrakis]

Even though you are not using this device anymore, in case you are ever interested, I just received a quote on the MMBFJ201:



/

 

[sonolink]

[Just the usual toggle switch you can find on any stompbox] -- I guess that the switches used on today's stompboxes must have changed considerably since the stompboxes I saw and worked on during the 60's and 70's. Back then, the switches were of a type far more heavy-duty than the ones you have shown. The switches used back then were more of an industrial-grade type. WOW!!!

I guess back in the day, size wasn't an issue for stompboxes. You can find industrial grade submini toggle switches today. I just linked you to the KIND of toggle switch used on stompboxes. Although I guess that if you've been seeing stompboxes since the 60's you must know far more about them than me...

[I usually never draw that part, and just add it when laying out because it's dead simple] -- Hmmmmmmmm.....While you are certainly free to design, build and operate in any manner that you wish to do so.....what you are doing is "not how things are done".....normally.

You're probably right. I guess it has to do with being self taught...or maybe perfect pitch, who knows?

While I do admit that my background with building electronic equipment is different than yours, one of the purposes of having a schematic is to have and to show what your circuit is -- WITHOUT -- needing to have anyone else perform "mental gymnastics" of filling-in the blanks of what your schematic is -- NOT -- showing!!! And.....I could certainly be wrong here, but.....I believe most all of the other members of this forum would agree that sharing an incomplete schematic really doesn't do anyone else any good.

Sorry for the "mental gymnastics" but my schematic is complete. No blanks to fill in. The LEDs are an extra that I added because I wanted, and isn't necessary at all for the circuit to work.

I'm not a designer and wouldn't dare to call myself anything near an EE. I am completely self taught in this, reading books, watching videos, reading papers, etc. I know my weaknesses and hate maths but one thing that I have always been grateful for and enjoyed the most here is LEARNING. In fact I feel the utmost respect for all those around here that have always offered me their knowledge, their time and their patience, without asking for anything in return, just for me to LEARN and try to understand a tiny bit more the awesome science and art of electronics. Thanks to them I have built and improved my building A LOT over time. I just can't imagine how many cold beers I owe around here. Thanks guys!!!

[Just feed one side of the footswitch with 9v so that when switched on it feeds the LED's resistor] -- OK.....so that just might be super simple, but.....now imagine if 10 other members of this forum asked you the same question as I did. You would have to reply to each of those 10 other members with the same answer!!!

Not really. They would read the first thread because they would have used the oh so useful SEARCH function in the forum. I'm sure you know what I'm talking about...

I just follow industry-standard "best practices and guidelines" and that seems to work well enough for me. But, what do I know???

Well from what you've showed so far, you seem to know everything, which I'm glad you do.

[This is my last schemo] -- I get the feeling that there isn't going to be any further "positive movement" here on your project, so I am merely going to drop-out.

I meant that the schemo I was posting was the last version with the last corrections, nothing else. Sorry if it came out as something that made you feel bad. English is not my mother tongue so excuse the language barrier, or if you prefer, you can post in Spanish. I'm quite sure the other members wouldn't mind...

But, you have your own personal ways of doing things.....which you are certainly free to have!!!.....and some of those methods run quite contrary to how I have worked designing electronic equipment for various aerospace companies, defense contractors, medical electronics firms, NASA, R&D laboratories and other types of electronics companies.

As I said before, I am self taught. I am deeply sorry for not drawing the LEDs and not deserving your help. I'll give a deep thought and introspection about my schematic manners tonight before I go to sleep.

So, I think it is best that you design, develop and build your stompbox in the manner that you are most comfortable with doing, without you having to learn and/or meet any form of accepted electronics industry practices or standards.

Thanks for the advice. I'll learn from someone else.
Good luck to you too

Cheers
Sono

 

[Newmarket]

...
Thanks for the advice. I'll learn from someone else.

fwiw your schematic looks pretty good to me. And easier to read than many "professional" schematics I've seen.
(not mine of course - always excellent - joke ).
Full component detail is properly contained in the associated BOM so imo it's fine to use judgement about what detail to include or show at schematic level.
With the diode pairs etc I'd suggest considering some text annotation to convey the intention and refer to BOM but it's not critical imo. The practical point is that you can then change only the BOM and not risk the schematic and BOM getting out of step. You're building an fx box. It would be out of scale to introduce rigorous change note procedures etc.
One thing I would suggest is to avoid having four way connections meeting at one point on the schematic. Conventions vary but my basic consideration is that a junction "dot / marker" can get 'lost' in hardcopy or even onscreen depending on size and resolution.
Let us know how it goes.

 

[Khron]

For what it's worth -

 

[sonolink]

Hi again guys,

I'm working on the PCB layout for this circuit now and I was trying to keep power traces at 0.5mm width but it's kinda tricky in some places. My question is: 0.3mm width for power traces in this circuit would be too thin?

Thanks
Cheers
Sono

 

[Khron]

What sort of currents are you expecting?

https://www.4pcb.com/trace-width-calculator.html

 

[abbey road d enfer]

I'm working on the PCB layout for this circuit now and I was trying to keep power traces at 0.5mm width but it's kinda tricky in some places. My question is: 0.3mm width for power traces in this circuit would be too thin?

Rule of thumb is 1A for 1mm width, with 1oz (35um) gauge, about 1.5A in 2oz gauge.
This is just for current rating, without prejudice regarding possible effects due to trace resistance.

 

[sonolink]

Thanks for that link Khron

What sort of currents are you expecting?

To be honest I don't REALLY know. I know that I need to provide the PSU with 9v/2A to feed the whole circuit. I know that B+ will be around 200-250VDC but I don't know how to calculate the current. I guess I'd need a Resistance figure to apply Ohm's Law but I don't know if I should calculate that for each resistor or the whole resistance....kinda lost here TBH...

https://ibb.co/k3vMPhz

 

[sonolink]

What sort of currents are you expecting?

https://www.4pcb.com/trace-width-calculator.html

Using that calculator, if I put 2A in "Inputs/Current" and 0.3mm in "Thickness" I get "Required Trace Width: 0.237mm" but I don't know if I need to input more data than just that...

 

[Khron]

The "thickness" there is, by default, 2oz/sqft, or 70um (70 micrometers, 0.07mm). Change that to 1oz/sqft or 0.035mm and see what you get then.

 

[abbey road d enfer]

Using that calculator, if I put 2A in "Inputs/Current" and 0.3mm in "Thickness" I get "Required Trace Width: 0.237mm" but I don't know if I need to input more data than just that...

Haven't you made a "finger error"? From the same calculator, I get 1.02mm with 2oz copper, and 2.03mm for 1oz.

 

[Khron]

One other value you'd need to input is the trace length (defaults to 1in there). The default 10C allowable temperature rise should be fine.

 

[abbey road d enfer]

One other value you'd need to input is the trace length (defaults to 1in there). The default 10C allowable temperature rise should be fine.

I checked that, just out of curiosity; it doesn't change the width. Of course it changes the electrical parameters such as resistance and losses.