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Beginner is Unsure about the PCB

Started by lg58, May 31, 2023, 05:44:33 PM

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Hi, I'm a beginner, 1/2 way through stuffing and soldering a preamp PCB I bought, but going to pause here. Don't  want to mention  the PCB seller, they could be skilled and legit, though not sure they're  on the Madbeans list of recommended links.  Something worries  me, plus I have some basic electronics knowledge  but not enough to verify a schematic/PCB. Strongly assuming a PCB for sale   is totally verified esp. before buyer gets parts and soldering.

So there's typos on the pcb seller's PDF and so far non-critical booboos on the PCB layout . But now I see something  in that schematic that I don't  get, it could be  something wrong , maybe...don't  know. The original non-clone schematic  is not readily available out of respect to the circuit designer - they might do another run of On vero layout blogs the equivalent verified vero project seems not to match the PCB schematic I bought if I seeing it right. As mentioned the original schematic not available. Of course there could be shorthand on the PCB seller's schematic I don't  get and everythings cool.

What do I do? I want to buy only PCBs I know are verified if I follow instructions correctly. Not that everything  has to be perfect...can I assume the recommended PBC links on Madbean  are usually OK people did the PCBs and verified?



If you'd like to post your build document, or a link to it, and if you can be a bit more specific about what's worrying you, someone here will certainly take a look.

Regarding the suppliers linked at the top of this forum, I've done business with most of them.  While there are sometimes things about a circuit design that I might have done differently, or occasionally a build document might contain an error, their PCBs have always worked for me.


If you're not going to say which board you bought and the specific troubles you're having I'm not sure there's anything people can do for you. If there is a specific circuit you want to build and want suggestions then let us know and you'll likely get some good recommendations from the people here.

Revisions of build docs, and differences between the docs and what's on the board are not uncommon, and many times it's just understanding which is most updated - again, something that someone here might (probably) know. Most of these makers tend to be one-man operations (as well as it being a passion) so it's good to give them the benefit of the doubt and just politely ask your questions and state your issues. They won't take it personally unless you're being a jerk, so just avoid that and you should be all good, dude.


OK. Just to preface, my electronics knowledge is basic, so I might ask something that's obvious or basic. I appreciate the effort by the PCB developer/maker to make this project available,  I emailed him about a typo on the PDF and he emailed me back fast and cleared things up.

So there's no 1uf film cap needed even though it's cited in the shopping list, and C3 is 1nf cap even though its footprint is way big on the PCB.

My immediate question is about C27 in the power section in the schematic diag. does that look correct?

Here's  the PDF:



C27 is fine, it's common to place a 100 nF capacitor at the power pins of an IC, in this case your TL074.  Some people would use two caps, one from VC+ to ground and another from VC- to ground, but one cap bridging VC+ to VC- is legitimate.  It provides a small power reservoir for IC1, and can help keep hi-frequency noise from the charge pump from coming into IC1 on the power busses. 

<edit> The only caution about C27 is to make sure the voltage rating of this cap is well above the difference between VC+ and VC-.  Example: If you're supplying 9V to this pedal, the charge pump will generate -9V, for a total difference of 18V, so you'll want a cap rated 25V or more.  If you're supplying 18V, the difference will be 36V, so I'd use a 50V or 63V rated cap.

C3 was probably changed from 1 uF to 1 nF after the PCB was designed, and the change made it to the schematic and BOM but not to the shopping list.  Notice there's not a 1 nF on the shopping list, but there's an extra 1 uF.


OK  thanks! Yes, for C27 got a 200v multi layer  NPO ceramic. It's  amazing  how small this cap is compared to the 63v film caps.


This place is great for beginners and pros alike.  You'd be surprised how many people a seemingly obvious question might help.  Welcome aboard!!!
Gordy Power
How loud is too loud?  What?