Getting some PCBs made soon. What's your preferences?

[Kevin Mitchell]

I'm finally working up a few projects that will be available to anyone interested. This will be my first time outsourcing PCB fabrication. I want to provide projects that the DIYSB folks could easily build with minimum inconveniences.

Some guide lines I'm doing my best to stick to;

• Economic pedal board real estate. I'm a fan of 125B boxes.
• Only common parts that are likely in your inventory (1/4w resistors, box film caps and so on)
• An option to acquire rare and oddball parts with the PCBs

What else could I add?
Also, any relevant suggestions are very welcome! I'm hoping sourcing fabrication isn't a trial and error kind of deal. Would be ideal to prototype but man do I hate etching double sided PCBs.


The projects I plan to release before the end of the year. Let's call it the start to the Retro series.
Retro Flange - a true A/DA clone with a few BBD options
Retro Vibe - a 125B Uni Vibe (I think you guys will dig this one)
Retro Synth - a Micro Synthesizer clone in a 1590BB.

I will announce a small give-away when it's time to cut the ribbon. My way of giving back to the folks I've tormented here over the years. You've been my mentors since 2014 and I wanna say thanks!

[bluebunny]

All looks good to me, Kevin.  If you can have value and designators on the silkscreen, that would be my preference.  Or just values, as a close second.  But not designators on their own!  Having to print out and constantly refer to a BOM in order to stuff a board is a pain.

Oh, and cheap shipping to the UK would be cool. 

[rockola]

If you can have value and designators on the silkscreen, that would be my preference.  Or just values, as a close second.  But not designators on their own!  Having to print out and constantly refer to a BOM in order to stuff a board is a pain.

I hate "just values" with a passion. No possibility to refer to the schematic to see what is where.

[Kevin Mitchell]

The way I see it as long as the build doc is well enough assembly should be a breeze. Also with a build like the Retro Synth some values would differ between the bass and guitar versions.

For a small build printed values are nice. But with bigger ones like each of the 3 I'm working up it may not be the best idea. Rockola has a good point. Debugging using my schematics without designations on the board would be a nightmare. Having both would crowd the board enabling one to misplace components. But we'll see!

I wouldn't leave the UK folks out! I'll publish the webpage with shipping details when the time comes. Usually stuff I send to the UK doesn't break the bank. My biggest gripe is when shipping exceeds the price of the item! But I doubt that'll be an issue.

-KM

[italianguy63]

If you can have value and designators on the silkscreen, that would be my preference.  Or just values, as a close second.  But not designators on their own!  Having to print out and constantly refer to a BOM in order to stuff a board is a pain.

I hate "just values" with a passion. No possibility to refer to the schematic to see what is where.

Plus, if you make a revision down the line, the PCB is wrong.  Much easier just to revise the BOM!

[Scruffie]

You could do a print out overlay of the parts values 

My only comment is 16mm right angle board mounted pots and preferably any switches too... god I hate off board wiring.

[ElectricDruid]

I hate "just values" with a passion. No possibility to refer to the schematic to see what is where.

Not true, in my view.  Like Scruffie said, it's easy enough to provide a reference image which shows what reference designator a particular thing is, if you need to know.

It's a lot easier to do it that way around than to have the refdes on the board and have to work out what each value is. Refdes on the board is an absolute *invitation* to people to put the wrong values in. Every single time they look, cross check against a list, pick a component, put that component in a hole in the board - each of those steps is a potential error, times by the number of components on the board. Arggh!
If you put values on the board, mistakes are less likely and then people don't need the refdes so much, because it should never have to come to heavy debugging.

I agree that it's much easier for the *designer* to put the refdes on the boards not the value, since you can mess about with the parts without having to update the PCB, just tweak the BOM. But that suits *you*, not the *builder*. That's the wrong way around. Put the part values because that's what the builder wants to see, and if *you* change the board, *you* have to do a new revision. Your problem, not theirs.

I'm also of the same mind as Scruffie on another thing - 16mm board-mounted pots and switches. The less off-board wiring there is, the less ways that can go wrong too. I'm trying to make this as easy as it can be for people. A rat's nest of wiring doesn't help at all, and it's horribly dispiriting when you build the whole thing and then fall at the final step.

These are the principles I try and aim for when designing boards for other people to use. Other people's aims and objectives may be different and their results will therefore be different too. That's all good. We don't have to do everything the same way, and there isn't one type of "best" that suits everyone.

For example, the downside of board-mounted pots and switches is that it ties you to one particular panel layout and orientation. If the pots are all hanging about on wires, there's more opportunity for people to rearrange things how they want them. Still, you can add wired pots to a board-mounted layout, and it's often impossible to do the reverse, so I'm still in favour.

Tom

[Rob Strand]

I agree that it's much easier for the *designer* to put the refdes on the boards not the value, since you can mess about the parts without having to update the PCB, just tweak the BOM. But that suits *you*, not the *builder*. That's the wrong way around. Put the bloody part values because that's what the builder wants to see, and if *you* change the board, *you* have to do a new revision. Your problem, not theirs.

These days with SMD parts sometimes I find it hard to find a good place for the designators,vnever mind the values, since it's so cramped in.   For through-hole the idea of putting the values *under* the parts seems a good comprimise.   The builder can see the value although they cannot check the value once it's placed.

In a professional setting you might have to do an engineering change for a part value and having the part value on the board then creates a problem because you have to update the PCB silkscreen to match.  If you re-issue the PCB then there's a risk something else gets stuffed up so you need to verify a lot more stuff.  If you don't touch the PCB at all then you *know* it's correct.   Managing change isn't something DIYers pay attention to but imagine a medical implant going into your daughter, you want to have some confidence that *any* chance of a stuff-up has been caught long before the implant got into the surgeon's hands!

[rockola]

I hate "just values" with a passion. No possibility to refer to the schematic to see what is where.

Not true, in my view.  Like Scruffie said, it's easy enough to provide a reference image which shows what reference designator a particular thing is, if you need to know.

My personal preference is for refdes/BOM as a builder. I also find reference images more cumbersome than reading the schematic and BOM. Others might feel differently.

It's not uncommon to have alternate values for some components. Which value do you put on the board? There won't be room for many alternatives.

If there are BOM changes (especially errata) after the board has been shipped, it's easy enough to update the build document. Sure, for new orders the board can be revised. I have a pile of to-be-built boards stretching back a number of years. Should I throw them away and order the new revision?

I just received an order from a supplier where they had shipped a C50k instead of the C500k I ordered. The value was right there on the component, and there was no PCB to stick it in. Mistakes happen. I am not convinced that "4k7" on the board is less error-prone than "R17" and BOM. In the latter case you do have to put in some (but not much) more mental effort. My belief is this mental effort works in favour of fewer errors. Not trying to convince anyone here, just sharing how I see it.

I'm also of the same mind as Scruffie on another thing - 16mm board-mounted pots and switches.  (...) Still, you can add wired pots to a board-mounted layout, and it's often impossible to do the reverse, so I'm still in favour.

This I agree with and for the same reasons, although I don't mind 9mm pots if it means the board can go in a 1590A. This would typically mean fewer than 3 pots.

[italianguy63]

Yeah, I reworked all my designs in the last year or so.. Everything has onboard pots, switches, and LED's now.  Only thing off board is the jacks, power connector, and stomp.  And I use a sub-board for the stomps too.. It really helps with build time and keeps things really clean looking.  I've moved most everything to 1590B's, and 1590A's when possible.  The pots also securely anchor the PCB in the enclosure too...

[ElectricDruid]

In a professional setting you might have to do an engineering change for a part value and having the part value on the board then creates a problem because you have to update the PCB silkscreen to match.  If you re-issue the PCB then there's a risk something else gets stuffed up so you need to verify a lot more stuff.  If you don't touch the PCB at all then you *know* it's correct.   Managing change isn't something DIYers pay attention to but imagine a medical implant going into your daughter, you want to have some confidence that *any* chance of a stuff-up has been caught long before the implant got into the surgeon's hands!

Totally agree. In a professional setting I'd go with Refdes every time, and I'd want a proper paper trail of ECUs for each modification/revision and etc etc. Designing for DIY and to make stuff easier for beginners is a different story entirely.

I am not convinced that "4k7" on the board is less error-prone than "R17" and BOM. In the latter case you do have to put in some (but not much) more mental effort. My belief is this mental effort works in favour of fewer errors. Not trying to convince anyone here, just sharing how I see it.

This is an interesting point. I wonder if anyone has ever tried studying that? Could you do an experiment where two groups get given a task, and one group's task is made deliberately more complicated, and then you compare error rates in the two groups? Fascinating stuff.

[amz-fx]

I agree that it's much easier for the *designer* to put the refdes on the boards not the value, since you can mess about with the parts without having to update the PCB, just tweak the BOM. But that suits *you*, not the *builder*. That's the wrong way around.

If you are just making a board with a single purpose I could agree that values are the way to go. For example, you are making a clone pcb of a classic circuit and need it made exactly like the original.

However, once you have mods to the circuit, it becomes difficult with just values on the pcb... there might be six 10k resistors and one of them should be changed to 15k, so which one is it? Sure, if the mods are simple and there is only one part on the board with that value, it would be okay, but still not ideal.

Also, if you make a pcb with multiple uses, you have to have only the part numbers on the pcb with no values (or it would be confusing).

Lastly, a builder has to be very careful during the construction, no matter what is on the pcb.

I print a page before starting a build, with an image of the pcb on the top half of the page, and the schematic on the bottom half. If a more detailed schematic is needed, I print that on the back of the page. If changes or mods are made to the schematic, I just write them on the schem with a pencil, or sometimes find a place to print the parts list... next to the pcb image, for example. Everything needed is on that page.

Best regards, Jack

[Rob Strand]

Quote from: rockola on Yesterday at 02:21:33 AM

    I am not convinced that "4k7" on the board is less error-prone than "R17" and BOM. In the latter case you do have to put in some (but not much) more mental effort. My belief is this mental effort works in favour of fewer errors. Not trying to convince anyone here, just sharing how I see it.


This is an interesting point. I wonder if anyone has ever tried studying that? Could you do an experiment where two groups get given a task, and one group's task is made deliberately more complicated, and then you compare error rates in the two groups? Fascinating stuff.

Yes, it is a good point.

Personally I don't have a problem following designators on the PCB and looking up the part value on a BOM.   There are different ways of presenting the BOM.  Like it's pretty common to bundle all the same part values on a single line.    In this case you would load-up all the same *values* first.  It would be possible to miss one position.   However, if the parts are kitted up-front  you would see one left over.   However you could present the BOM in numerical order.  It would force you to go through one at a time but really it's not as efficient as bundling the values.

Many  assembly houses will load up multiple boards at a time.   So they are either all right or all wrong.   One  safety net is to have a reference board, or load a single board first which is then checked.   You look-up the part on the BOM and you check the value against the reference board before loading the part.     People will still stuff-up if there's different markings on the parts like 4-band resistors on the reference and 5-band resistors in the parts bin.   Nonetheless it can reduce the errors.

I have had bad builds of machine loaded SMD boards where someone has mixed two part types in one of the part bin!    At the end of the day I don't interfere with how assembly houses work.   I only get involved when there's a stuff-up.   They all have their own production recipies.

[Ben N]

Just chiming in--from a paint-by-numbers POV, values are easier than schem refs, but not overwhelmingly so, and that advantage is lost if there are any mods or part substitutions. Plus, once the board is populated, you can't see the silk screen regardless, so the choice becomes moot for troubleshooting. So values or schem/BOM refs, either way is ok. But having an image of the pcb with schem refs in the build doc is absolutely critical to any kind of troubleshooting, IMHO.

[ElectricDruid]

But having an image of the pcb with schem refs in the build doc is absolutely critical to any kind of troubleshooting, IMHO.

Totally agree. Jack made the same point too - good documentation of what goes where is crucial.

[r080]

This might seem stupid, but for the documentation, I occasionally get myself confused when two columns of part designators/values are close together. In this contrived example below, I would have a tendency to accidentally grab a 10k for R4.

R1   4.7k  R4   2.2M
R2   47k   R5   10k
R3   5k

[amz-fx]

This might seem stupid, but for the documentation, I occasionally get myself confused when two columns of part designators/values are close together.

Occasionally, on a complex build, I use a highlighter to mark out the parts as I place them on the pcb. This will reveal any that are missed when you think you are finished, and are reviewing the project.

regards, Jack