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Tech Chat Manufacturing your own PCB

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Till Eulenspiegel
(@till)
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I doubt if anyone would go to trouble of making a complex printed circuit board by using the old method of laying on pieces of crepe material on the grid pattern. sheet.   Made sometime in the late eighties or early nineties a 405 sync and blanking board for a 405 line converter project. No CAD assistance.

405 BLkg Sync

Till Eulenspiegel.

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Topic starter Posted : 27/11/2021 12:08 pm
colourmaster, Red_to_Black, Lloyd and 1 people liked
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Cathovisor
(@cathovisor)
Illustrious V-Ratter Registered

@till 

I remember my colleagues at work doing just that though - and a step below that was the "Dalo" pen. Later on, when CAD packages and UV-sensitised boards became available a couple of friends made their boards using laser-printable OHP film, being careful not to accidentally produce a "Doppelganger*" and passing the film twice through the printer to get sufficient density.

 

*this was where you accidentally produced a mirror-image of the track layout.

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Posted : 27/11/2021 12:33 pm
helloekco
(@helloekco)
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Posted by: @cathovisor

Later on, when CAD packages and UV-sensitised boards became available a couple of friends made their boards using laser-printable OHP film, being careful not to accidentally produce a "Doppelganger*" and passing the film twice through the printer to get sufficient density.

This is what we did on my GCSE electronics course in the early 90s, except that we used a plotter to create the transparency.

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Posted : 27/11/2021 2:33 pm
Till Eulenspiegel
(@till)
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 I understand the BBC digital 625 to 405 line converter PCB artwork was made in a similar manner.  

Till Eulenspiegel.

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Topic starter Posted : 27/11/2021 3:37 pm
Cathovisor
(@cathovisor)
Illustrious V-Ratter Registered

@till It's a pity D&ED no longer exist to ask them, unless there's an issue of Eng Inf that mentions it: when they were the only show in town you could understand the BBC making all its own equipment. I think one of the last studios to use BBC Coded Equipment was TC5 in its last analogue refurbishment in 1986. It also had a digital video decoder and a digital vision mixer (called a "combiner") for the graphics area.

It was certainly using the BBC-designed analogue video DAs right up to its closure in 2011.

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Posted : 27/11/2021 5:23 pm
WayneD
(@wayned)
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The only pic I have of my prototype attempts from 2013. I used a CFL bulb as a UV exposure and it worked very well. I drew this in MS Paint and printed it onto an overhead projector transparency. The big gap in the bottom left was eventually used for something else.

FB IMG 1638031923486

 

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Posted : 27/11/2021 6:05 pm
Jayceebee
(@jayceebee)
Noble V-Ratter Registered

Many years ago I constructed the PW mag Tele-Tennis, lots of TTL ICs on several boards. They were drawn by hand with a Dalo pen and although not pretty they worked. later I tried those rub on pads and tracks but were a bit of a pain.

I'm currently working on a replacement field board for Chris's 4000 using the toner transfer method. I've not attempted this before but seems to be possible to produce good results. Unfortunately I don't have a laser printer but a work colleague is helping me out with this. 

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Posted : 27/11/2021 9:04 pm
Jayceebee
(@jayceebee)
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Posted by: @cathovisor

..... being careful not to accidentally produce a "Doppelganger*" .

Something woke me at 3am the other day and that exact thing came to mind and that I needed to mirror the design 👍 

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Posted : 27/11/2021 9:26 pm
WayneD
(@wayned)
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Posted by: @jayceebee

Many years ago I constructed the PW mag Tele-Tennis, lots of TTL ICs on several boards. They were drawn by hand with a Dalo pen and although not pretty they worked. later I tried those rub on pads and tracks but were a bit of a pain.

*shudders* oh I remember the rub on pads and tracks! Took about 10 times as long to draw something out. I preferred the stencils but even then I'd just use it for the pads and still draw in the tracks by hand.

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Posted : 27/11/2021 9:31 pm
WayneD
(@wayned)
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Posted by: @jayceebee

I'm currently working on a replacement field board for Chris's 4000 using the toner transfer method. I've not attempted this before but seems to be possible to produce good results. Unfortunately I don't have a laser printer but a work colleague is helping me out with this. 

My Father in-law (ex-technology teacher) has had really good results with this. He doesn't even bother removing the toner from the copper afterwards apart from the actual solder pads. He's found takeaway menus seem to work best to print the toner onto first before transferring it to the copper clad board.

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Posted : 27/11/2021 9:38 pm
Jayceebee
(@jayceebee)
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@wayned I’ve seen one technique using that involves magazine paper and nail varnish remover, no heat involved. It seems to give amazing results.

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Posted : 27/11/2021 10:25 pm
crustytv
(@crustytv)
Vrat Founder Admin

Does anyone here have experience with Eagle PCB design and Flatcam?

I've been struggling with getting to grips with Kicad and Eagle software packages. Mainly around how you replicate a pre-existing board, such as the 4K.

I all but gave up, then around 05:00 this morning, my brain woke me up and said, "maybe you can do what you mentioned the other day, import an image", I had to get up. So I took the image John had been using for his etch (a scan of the manual) to give it a try. I resized it for the board dimensions, 160mm x 95mm, and converted to a bitmap.

Thorn 4000 Series Vertical Deflection PCB: Monochrome Bitmap

4kvdfboard

Then loading eagle, I created a board project, then run a ULP script for importing bitmap images. Chose the import colour, in this case white. Then select the layer to import to, and finally the DPI which I set to 600. This generated a suite of script commands that I then executed. This resulted in the image slowly importing, until you see what I have in the image below. The left-hand side of the photo shows the image imported to the PCB. The blue is the assigned layer colour, as you can do multi layers.

Next, I ran the CAM processor on the newly created board in eagle, to generate the all important gerber files. Then loading up Flatcam which is the CNC software, I created a new project and imported the gerber files, that I had just exported from Eagle. The job started and looked to take a while, so off I went for a cuppa. Upon my return, I had the PCB now imported to Flatcam. This is shown on the right-hand side of the photo below.

design

I believe what I have to do now is generate the CNC commands that will mill out the traces, now this is where I'm stuck. If I had been doing this properly, each individual trace of the PCB would be an object, however, it is in effect one trace. Normally, you would define parameters for each trace, setting the milling spacing etc, obviously I cannot do that in this case. I'm wondering if I generate a basic CNC command set that it will reproduce what I have, the spacing should be sufficient.

So this query is to anyone who has experience in the above, or a big ask, can anyone recreate the board in kicad and send me the gerbers?

 

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Posted : 17/12/2021 9:40 am
irob2345
(@irob2345)
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There may be a chance I can do this over the Christmas break, depending on family commitments.

I use Altium Designer. The board I'm doing at the moment at work has lots of 0201 passives.

SMD sizes

I normally start with a schematic and library components which are linked to the board.

Using 0805 and larger SMDs (which are easy to hand solder using tweezers) I could put the whole lot on one board, no thick film modules.

Generating the gerbers once the board is designed is the click of a button.

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Posted : 17/12/2021 10:20 am
crustytv
(@crustytv)
Vrat Founder Admin

Hi Ian,

as much as I appreciate the thought, there is no way I would want to go down the surface mount route.

Two reasons, one I cannot work on things so tiny, secondly and most importantly to me, it's so out of keeping for the period, I like to keep as close to originall where possible. Surface mount is not something I would wish to see anywhere near in a 70's or earlier TV. Rightly or wrongly, it's a matter of personal opinion and choice, I'm sticking with through-hole. For example, I've even managed to find a whole raft of NOS Thorn thick-films for the 4K, so will be using them and not the ones I've spent ages building. Though the process was valuable as I will be able to make my own should the need ever arise.

I appreciate you and possibly others, will think this is foolish, that I'm just continuing the unreliability Thorn manufactured in the first place, but as I say, each to their own choice.

I've bought a PCB CNC milling machine, milling bits and some PCB blanks, hence trying to get to grips with the process. Which is to replicate the 4K traces in Kicad or Eagle, export that as gerber, then import that into Flatcam, (CNC software) and finally to generate the CNC commands. Weirdly, the latter would appear to be the simple bit.

PCBproduction

Hopefully as time passes I will gain experience in teh use of PCB design software and this will all become a simple affair and second nature. At which point I will be able to tackle and recreate a G6 decoder, as the CNC machine can create boards up to 12" x 7.1". Then, if I ever need to make a PCB for a TV, I will have the means to do so, I believe John needs to manufacture something for a A823 he has.

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Posted : 17/12/2021 10:37 am
irob2345
(@irob2345)
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I do understand where you are coming from and the point is well taken.

I suppose, since you aren't worried about including holes in the gerbers, that pattern could be imported into Altium as a silk screen layer and traced using polygon pours. That would give you an output that you could use since it's all vector mapped.

Do your available tools have a polygon copper pour feature? If so it might be worthwhile learning to use it.

I know many people are frightened of SMD but I'm a convert. Using 0805 passives and SO chip footprints (not the really tiny stuff which can really only be handled by robots) results in a board that's quicker and easier to assemble by hand than the same thing when laid out in through hole. It's a matter of technique. I just tin a row of pads for one side of the part and slide the part in with the tip of the iron on the end of the part. Then you go back and solder the other ends.For ICs, you use a similar technique to tack the part in place. Then solder all the pins in a row without worrying about shorts. Then place a length of solder wick along the row and heat it to remove all the solder between the pins.

I should point out that I'm 72 and suffer from mild Parkinsons so I don't have especially steady hands. If I can do it, anyone can!

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Posted : 18/12/2021 11:31 am
crustytv
(@crustytv)
Vrat Founder Admin

I've spent yesterday evening and this morning tidying up the image John provided, in Adobe Photoshop. In my opinion, it's now a lot better with fewer jagged edges. I removed the holes (not my doing) from the trace image, as I can allegedly generate a drill map in the CNC software. Find out later today when it all arrives.

The physical board dimensions to fit the Heatsink frame are 160mm x 95mm

rsz 1latest1   copy
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Posted : 18/12/2021 11:34 am
Cathovisor
(@cathovisor)
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@crustytv 5mm narrower than a standard Eurocard, I note.

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Posted : 18/12/2021 12:56 pm
crustytv
(@crustytv)
Vrat Founder Admin

Santa just delivered my Christmas present early, now to get assembling........ Back later with hopefully something that resembles a CNC.

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Posted : 18/12/2021 4:15 pm
crustytv
(@crustytv)
Vrat Founder Admin

3hrs 15 mins later, it's built. Time for some nibbles and a drink, then install the software and do  a setup.

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p.s.

The little controller, allows you to run the CNC free of being connected to a computer. There is an SD card slot on the back, you copy the PCB design you intend to print to it, that contains the CNC commands which are then executed. There is a tiny display screen, yet to see what the menu system is like.

I may make use of this feature, rather than having this on my main workbench. This flexibility allows me to set it up on the bench in the stockroom. I can design on the main pc and then just copy it to the SD card.

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Posted : 18/12/2021 7:42 pm
peterscott, jcdaze, ntscuser and 3 people liked
crustytv
(@crustytv)
Vrat Founder Admin

The bulk of the build is done. The CNC was connected to the computer and some tests carried out. There were some bugs to start with, main two were it not automatically finding the machine, and the other was slippage of the baseplate. Just a short video, as I've been at this since 3pm and I now need my bed. I bet my mind won't let me relax, it will be planning the next steps, John will know the active mind problem.

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Posted : 19/12/2021 12:25 am
jcdaze and peterscott liked
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