Copying an existing small PCB board?? - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: April 22, 2014, 01:39:38 pm
content: I have a small edge connected PCB from a now working Farnell power supply unit. (Thanks Jerry, "fankl" on this forum). I have another, bigger, 50 amp, 60 volt Farnell supply I bought dirt cheap that I think has a shorted pass transistor and this board is also missing. The missing board is identical to the one in the working, smaller power supply though. I am unsure how to duplicate it. Whether to photograph it and try and create a photo resist template, and etch a copy? I am familiar with the photo resist manufacturing process at the hobby level and have done several boards successfully, but from existing commercial artwork. Or should I attempt to hand draw the tracks on photo resist, with etch resistant pen, and etch? Or to make it on Veroboard and hard wire the edge connectors? I would prefer to do a proper copy onto photo resist, to be frank. Does anyone know the likelihood of converting a decent photo of the single sided board's tracks into a pure black and white image I could print on to the clear photo resist paper? I am hopeless at art work using computer graphics programmes, but even more hopeless at hand drawingI have put photos of both sides of the board athttp://www.chriswilson.tv/experiment1.jpgandhttp://www.chriswilson.tv/experiment2.jpgin case they are too big to attach here.Thanks.

author: con-f-use
author_rank: Unknown
timestamp: April 22, 2014, 01:58:35 pm
content: It's one sided and fairly large through hole components only. So this should work nicely:- Put the board on a flat bet scanner or photocopier- Experiment on paper to---- a) make sure it will do a 1:1 size ratio copy---- b) set the hue, saturation and contrast right for the tracks to show as negatives- Copy it on transparent foil- Use the foil as mask for your photo resistShould be the easiest and quickest way for a one off. Transparent foils are easy to come by and I guess you already have broads with resist on them and the developer for those. So very cheap as well.

author: Unixon
author_rank: Frequent Contributor
timestamp: April 22, 2014, 09:12:30 pm
content: If you want perfect result, reverse engineering and redesigning the board in EDA may be considered a viable option (IMO).

author: tautech
author_rank: Super Contributor
timestamp: April 22, 2014, 09:30:18 pm
content: I'm with con-f-use on this one, although you will need to tidy up the existing PCB.You might need to suck some solder off the pads where clearances are tight and also snip component leads where they lay over.The fiddly bit will be drilling, as you will not have a center guide.Having an artwork program, I would redo/update the layout, however it is not at all a dense or complex PCB and his process or similar should work just fine.

author: janoc
author_rank: Super Contributor
timestamp: April 22, 2014, 10:06:06 pm
content: Indeed, just redraw the board in an EDA tool. It would look much better and considering the simplicity of the thing, you will likely have faster and better result than trying to copy it using a scanner or something like that.

author: Chris Wilson
author_rank: Super Contributor
timestamp: April 26, 2014, 07:56:46 pm
content: For completion I thought I'd post how I got on. I don't have a scanner, and am hopeless with PC based digital artwork applications, so I traced the tracks onto clear acetate film, using an overhead projector pen (Lumocolour 318, in black). I then used photo resist broad and my UV box to transfer to the PCB. Whilst it's not the prettiest thing in the world it should be functional. it fits the edge connector socket, and in case anyone spots the (deliberate?) mistake, I have moved the electrolytic to its correct one set of holes lower on the board. Just awaiting the rest of the components to fully populate it now, cheers guys!

author: tautech
author_rank: Super Contributor
timestamp: April 26, 2014, 11:05:09 pm
content: Yep that's ugly. But it does not matter for the intended application.Shame you did not challenge yourself to have a go with a PCB program. An EASY board like this would have been perfect to start with. You might have even gone to a mix of TH & SMD.I see you have tinned the tracks, you could have used a PCB lacquer, some of them are solder through, perfect for protecting homemade PCB's before & after you populate them.

author: Chris Wilson
author_rank: Super Contributor
timestamp: April 26, 2014, 11:20:34 pm
content: I would love to have a go with a PCB design programme, but I have a use for this supply, so I need to just get it up and running. I may well have a play either making a better looking one, or something else in due course. Got much to learn, and would love to see how novice friendly these programmes are. Cheers.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 27, 2014, 05:05:50 am
content: Ugly? For hand drawn, not too bad honestly. I think it's pretty coolTim

author: at2marty
author_rank: Regular Contributor
timestamp: April 28, 2014, 03:19:07 pm
content: Quote from: T3sl4co1l on April 27, 2014, 05:05:50 amI second this. In my opinion it's pretty good work!

author: Chris Wilson
author_rank: Super Contributor
timestamp: April 28, 2014, 03:36:31 pm
content: Quote from: at2marty on April 28, 2014, 03:19:07 pmThanks, and more to the point, it's now fully populated and workingI would have loved it to look more "professional", but as long as it's reliable and works I doubt anyone bar here and myself, will know it's a bit naff

author: G7PSK
author_rank: Super Contributor
timestamp: April 28, 2014, 04:21:39 pm
content: Get some printers ink, paint the traces then put a piece of paper on something softish and push the board onto the paper any wire protruding will push through the paper allowing the traces to contact evenly then just photo copy the print and touch up the copy as required.

author: krivx
author_rank: Frequent Contributor
timestamp: April 28, 2014, 04:26:52 pm
content: If you want to clean it up you can wick away the excess solder on the traces. You'll never remove it all, so you usually end up with a thin, even solder layer over the copper. It can look pretty neat.

author: jancumps
author_rank: Unknown
timestamp: April 28, 2014, 05:07:46 pm
content: Well done! You'll need to do something with the connector slot to prevent those copper traces to oxidate.

author: at2marty
author_rank: Regular Contributor
timestamp: April 28, 2014, 10:31:37 pm
content: Quote from: Chris Wilson on April 28, 2014, 03:36:31 pmDon't be so hard on yourself, you did a wonderful job. One thing that comes to mind that I wonder about. I've never tried it, but I wonder if the photo resist method or something else would work on the top side of a board like that? It would be nice to have a "silk screen" to at least identify parts on the top side.