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Old 25th May 2019, 4:24 pm   #1
Chris55000
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Default PCB Layout Diagrams in Service Manuals?

Hi!

Just a quickie one!

Can anyone point me in the direction of a method Manufacturers/OEMs use to produce PCB layout drawings like this Roberts R900 example attached please?

I saw an "instructable" on how to do it once, but now I can't find it any more!

Chris Williams
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Old 25th May 2019, 8:21 pm   #2
julie_m
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Default Re: PCB Layout Diagrams in Service Manuals?

Nowadays it's something that would be done directly from the PCB CAD software. Pre-computers, it would have been done using traditional photographic and printing techniques to superimpose the copper artwork (mirrored to look like an X-ray through the board) and silkscreen (right way round) films together.
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Old 25th May 2019, 8:51 pm   #3
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Default Re: PCB Layout Diagrams in Service Manuals?

Modern PCB CAD almost requires you to define components to silly levels (even colour and surface finish), great for 3D CAD exports, bad for speed of design.
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Old 26th May 2019, 1:11 pm   #4
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Default Re: PCB Layout Diagrams in Service Manuals?

Depends what you mean by speed! Being forced to define the component in 3D means there's a much better chance that the finished board will actually fit together properly, which matters a lot when someone else is putting it together. And the pretty 3D view that modern CAD software will produce is very good for keeping clients happy, I find...

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Old 26th May 2019, 6:53 pm   #5
julie_m
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Default Re: PCB Layout Diagrams in Service Manuals?

Of course, it's purely by dint of the sheer power and complexity of the software that it's more effort than it's worth to define your own component models from scratch when there are "accessory packs" available from the CAD vendors for such a reasonable sum, and absolutely not deliberate on the part of the vendors.

And if you believe that, I've got an investment opportunity you're going to love .....
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Old 27th May 2019, 10:37 am   #6
DonaldStott
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Default Re: PCB Layout Diagrams in Service Manuals?

I'll be adding a Post to my Turntable Stroboscope Thread in Homebrew Equipment later but just thought I'd Post my own views after having struggled with Eagle software for some time - why is it so difficult to use?

My circuit diagram evolved over time as my Breadboard prototype grew in scale and complexity when more stages were added. I started off with the trusty pencil and paper but quickly moved to using Microsoft Paint which allowed the use of different coloured lines for my connections. Made it easier for me to follow the signal paths but have to admit that it's almost painting by numbers!

I realised that at some point I would need to convert the circuit diagram to a PCB but my manual skills in that area are woefully lacking. So I had a go at using Eagle software to create a schematic from my circuit diagram and after much wailing and gnashing of teeth I finally have one. In the Eagle software there is a tool called Electrical Rule Check (ERC) which, as you can guess, checks for common errors in your schematic - fortunately I have no errors.

Next stage is to use the Generate/Switch to Board command which (allegedly) converts the schematic to a PCB layout - this is the stage I am at currently with a PCB layout that shows a jumble of components and a tangle of spaghetti! It's possible to move everything, components and connections, and to resize the board (and much else) but I don't know if I have the staying power for this ... hopefully my "stubborn" gene will kick-in at some point and I will persevere.

Hope I haven't strayed off-topic too much but just wanted to let the OP know my own experiences of trying to get to a PCB from a circuit diagram.
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Old 27th May 2019, 11:49 am   #7
cmjones01
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Default Re: PCB Layout Diagrams in Service Manuals?

Quote:
Originally Posted by DonaldStott View Post
Next stage is to use the Generate/Switch to Board command which (allegedly) converts the schematic to a PCB layout - this is the stage I am at currently with a PCB layout that shows a jumble of components and a tangle of spaghetti! It's possible to move everything, components and connections, and to resize the board (and much else) but I don't know if I have the staying power for this ... hopefully my "stubborn" gene will kick-in at some point and I will persevere.
Some people will tell you, and I'm one of them, that the art of a good PCB layout is in the component placement. There is no software on earth which can make a good job of this, as far as I'm aware. It's a manual task, best suited to the human brain.

I do a certain amount of this professionally. The last board layout I did contained nearly 380 components, so the tangle of wires would have been completely unmanageable! The way I like to do it is to import a small number of parts from the schematic to the board at a time, in reasonably logical chunks (power supply, amplifier stages, CPU, output stage, whatever makes sense for your project). Then you can roughly lay out each chunk without getting lost. I find it helps to be able to see the schematic diagram at the same time - print it out or view it on a second monitor. Then you can place the components in a sensible way, so those connected to each other are close to each other, and the right way round, and so on.

Once each little chunk of the circuit is placed, you can move them around and adjust them to snuggle neatly together in to a board layout. Make sure there's space for the component identifiers if you're adding a silk screen layer.

Once this is done, adding the tracks between the components is actually the easy bit.

A result of all this should be that your CAD software will produce, among other things, a diagram like the one in the original post, which I'd call an 'assembly drawing'. It's up to you to put the component identifiers in the right places, of course. I always include one in the package of data I send to the manufacturer. It makes talking about the board and finding problems much easier.

Chris
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Old 4th Jun 2019, 10:40 am   #8
DonaldStott
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Default Re: PCB Layout Diagrams in Service Manuals?

Thanks Chris - fully appreciate that component placement is a manual task and in my case this simply involves using the Move and Rotate tools in Eagle.

Apart from your very sensible approach "...to import a small number of parts from the schematic to the board at a time, in reasonably logical chunks ..." I just wondered if there were any good design or best practice principles available that should be applied?

I also note that you " ... do a certain amount of this professionally..." so any advice or guidance based on your experience would be welcomed.

Next step, routing those tracks between components...!
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Old 13th Jun 2019, 10:52 am   #9
David G4EBT
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Default Re: PCB Layout Diagrams in Service Manuals?

The original query was 'what do manufacturers use?'

I can't answer that, but I would say that what CAD is used professionally, and the level of skill called for, goes far beyond the needs of hobbyists, unless for example, they wish to get PCBs professionally made by sending Gerber files to a PCB maker. (The picture in the first post was of of course a component overlay rather than a PCB track layout).

I've designed and made my own PCBs for countless home-brew projects over the years and have never found any of the programs generally used by hobbyists for DIY production techniques to be at all helpful. The programs are geared to professional production techniques and examples of artwork produced by hobbyists that I've seen are a recipe for failure when it comes to etching and drilling. The main reason I say that is that invariably the tracks are too thin, inconsistent in width and the pads are needlessly small, leaving little copper on the PCB, risking undercutting when etching, damage to the pad when drilling, and lifting of the track when soldering. It may of course be that the designer isn't especially adept at using the CAD package to take account of amateur production techniques.

The first pic below is example of a small section of a PCB that was published in a magazine some months ago for a SW receiver, which I think was produced using Express PCB. In the top picture the track thicknesses are inconsistent and the component pads needlessly small, especially for the two transistors. At one point there is a hole at a right angled corner with no 'pad' to reinforce the track. The lower picture is how the artwork could, and should have been produced to ensure that it could be etched, drilled and soldered with minimal risk of failure. That's especially important when - as is sometimes the case, the hobbyist is making do with a standard pillar drill to drill the PCB, or even trying top use as Dremel type drill freehand.

When etched, the pads on the original design would have been further weakened by 'undercutting' in the etching process. Etchant doesn't just etch downwards, but sideways too, so as etching progresses the area of copper that has the longest duration of etching is just below the etch resist, as shown in the second pic, making the tracks and pads even more fragile.

I've not set my face against PCB CAD programs, which do marvellous things such as multi-layer boards, auto-routing and so forth, and I dare sat that for those experienced in using such programs will echo my sentiments that the design in pic 1 below is not a good example, but it's typical of many that I've seen.

I design and produce maybe ten PCBs a year for my home-brew projects. That involves drawing the circuit, the component overlay and the PCB artwork for the mask. I also clean up indistinct circuits for radio restorations, design front panels, and routing patterns for radio back panels, along with occasional sketches connected with radio restorations. For all of those applications I just use 'Paint' which comes free with Windows (till MS swing the axe and kill it, which is their avowed intent).

Some PCB designs can be further adapted using 'Paint' or something similar to leave as much copper on the board as possible, which speeds up the etching process, and makes the drilling of holes less critical should the drill not be quite on target. In the third pic below, the two PCBs look quite different, but they're the same basic layout. In the picture on the right, the PCB could be created by using sticky backed plastic (eg: white Fablon) applied to the PCB, the paper design stuck onto the Fablon, and the waste areas cut away with a modelling knife.

Often, makers' data is scruffy and indistinct, and I use 'Paint' to clean up or re-create the circuit and other diagrams. Pic 4 is a section of a Unitra 'Figaro Special' circuit, and pic 5 shows it after I'd re-created the circuit to clean it up.

I hope that's of interest and use.

I'll attach a few more pics in another post.
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Old 13th Jun 2019, 11:42 am   #10
David G4EBT
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Default Re: PCB Layout Diagrams in Service Manuals?

A few more pics all created using MS 'Paint' relating to my restoration of a Unitra Figaro Special.

It might seem a lot of fuss about the restoration of a simple set and I dare say I could have got by without what to some may seem like too much of a palaver. However, I find it far more tedious to try to work from scruffy, indistinct service data or scrappy freehand sketches. In creating those drawings I identified several circuit errors. I was also able to create a back panel from a photo I found on internet (missing from the set when I bought it).

I don't see this as a needless chore that I could well do without, but as part of my hobby.

Hobbies are about the relaxing, enjoyable and productive use of scarce leisure time. There's no economic case to be made for making one's own PCBs, when they can be bought more cheaply, just as it makes no economic sense for me to spend a morning making a little comb-jointed mahogany box for a project I've built when an ABS box could be bought for under a fiver and would do the job just as well. If I didn't enjoy it I wouldn't do it.

Pic 1: Below chassis diagram.
Pic 2: Auto transformer tag identification.
Pic 3: Output transformer tag I.D.
Pic 4: Dial cord, IFTs and DM70 magic eye connections.
Pic 5: Replica back panel.

Perhaps these notes aren't really relevant to the original query, ('what software do makers use?') which I can't answer, but hopefully, some pointers as to what we hobbyists can use. I've posted lots of examples of home-brew PCB projects I've designed using MS 'Paint' - most recently in the Donald Stott 300Hz strobe project thread.

Hope that's of interest and use.
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Old 13th Jun 2019, 6:43 pm   #11
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Default Re: PCB Layout Diagrams in Service Manuals?

When I was doing PCBs for a living, I made a point of adding freehand shapes to maximise the amount of copper and minimise the amount of work to be done by the etchant; especially as I knew it almost certainly was going to fall to me to etch, drill and build up the prototype, so I might as well make it easy on myself.

Apropos of not much, a time-lapse movie of a reasonable size expanse of copper being etched away looks a lot like how a forest fire propagates. That should not be too surprising, since both processes are chemical reactions and the disposition of the reagents is similar -- a thin layer of a solid reagent on top of an inert substrate, all immersed in a fluid.
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Old 13th Jun 2019, 7:02 pm   #12
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Default Re: PCB Layout Diagrams in Service Manuals?

Quote:
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When I was doing PCBs for a living, I made a point of adding freehand shapes to maximise the amount of copper and minimise the amount of work to be done by the etchant;
That would have been anathema in a 'serious' production-environment.

Why?

Because the old copper-rich etchant was a profit/social-merit-centre - sold on to a recycling company and the more copper there was in it, the more-valuable it was! (and the more 'points' your company could boast about for its toxic-waste-minimisation strategy)
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Old Yesterday, 9:54 pm   #13
Chris55000
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Default Re: PCB Layout Diagrams in Service Manuals?

Hi!

Altho' not free, Abacom's Sprint Layout is ideal for those who have a good sense of "spatial awareness" and was designed for hobbyist use where the complex routing algorithms of purpose–made PCB design tools like Eagle, Kicad, Easy–PC, Altium Designer, etc., are overkill for a simple basic design.

Sprint is particularly good on analogue pcb layouts where large areas of copper need to be blocked in, and it will also do "ground plane copper–pour" as well.

It compliments their sPlan Circuit and Diagram draughting tool, which I find perfect for the types of circuit–diagram used in this Forum, and I'll add I bought them both at full retail price from Abacom and am a very pleased user of their products!

Chris Williams
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