So I’ve got my TV Typewriter ‘mainframe’ parts install underway.  I’ve got molex connectors, caps, diodes, resistors — the whole nine yards.  I decide to put the board up against a light to check for any trace ‘bleeding’ or accidental solder bridges and then:

Not good.   Not good at all!

This is something any homebrew PCB maker should check before proceeding.  I had been fooled — from topside, the copper obscures the tiny pinholes visible here.  Since these pinholes look like the pattern of pixels in a magazine photograph, I’m guessing not enough toner was deposited to fully protect them from the etchant.

Interestingly, the traces all test good on the ohmmeter.  I’m tempted to carry on – but this state of affairs really bothers me.  More experienced hands warn it will eventually fail.  So I decide to switch to the second mainframe board I made — that one passes the backlight test handily.  I’ll wipe the black silksreening off it, clean it up, check it, and transfer everything over.  Thankfully the mainframe doesn’t have too many parts installed!

So now I’ve got my TV Typewriter ‘artwork’ all finalized and I’m ready to try a transfer.  I don’t have any special toner transfer paper — but I do have magazine stock.  My first attempt is using pages cut out from a Macleans magazine.  The first couple runs are surprisingly easy – the printer takes the sheets and passes them through without fuss.  With one sheet done, I decided to take a run at it with the iron and see how the transfer worked.  And I had to use iron because I didn’t have a laminator handy — there were none available at any of the stores in town and I was just getting too impatient to get going.  Plus, why spend money if you don’t have to, right?

I put the iron on the hottest setting and pressed and ironed for what felt like an eternity but in reality was only about 10 minutes.  My arms ached.

I then took the hot PCB (with oven mitts, eventually, after discovering by accident how hot it really was), rinsed it in my sink and peeled off the paper.  Damn.  Almost.. but still some traces missing.

I spent the rest of the evening trying various things without success.  Longer ironing time, more pressure.  Started to wonder about the toner I was using — like many, I skimp a bit on that and use remanufactured cartridges.  I’ve heard these sometimes have less plastic in them (the stuff that melts), and the result is they don’t transfer as well.  But before I go and buy a $200 OEM toner cartridge, I figure maybe I’ll try everything else I can, including changing papers.   It’s possible this isn’t going to work — most of the toner transfers via iron I see demonstrated on youtube involve much smaller PCBs.. far easier to apply consistent pressure and heat.  But I’m not giving up yet.

I get out some acetone and wipe my test board down.  Then I try parchment:

You’d think parchment would a shoo-in — it’s slippery stuff.  I thought for sure once heat was applied the toner would just jump right off.  Nope.  All it did was smudge a little.  Argh!

As a last ditch resort, I figured I’d try higher quality paper.  By this point I had already ordered Press N Peel, but that’d be a week or more of waiting and I just couldn’t wait that long.  I grabbed a Hotrod Magazine from my pile and noticed the paper was just a bit thicker and shinier than the Macleans stock.  I gave it a try.  I discovered right away though that I had a problem – the traces were not printing at full darkness.  They would on regular paper, but not this Hotrod stock.  After fooling around for an hour, I realized my issue was that I wasn’t giving the printer the proper setting for printing to glossy paper.  What you needed to do was actually tell it you were printing to heavy glossy in Photoshop’s print settings dialog.  Doing that caused the printer to request the sheets via the manual feed tray (I had just been slipping them into the regular paper bin, causing the odd error/jam).  I noticed right away a big difference — set to heavy glossy, the printer pulls the paper through more slowly, reducing the risk of crease and I guess giving more time for the toner to adhere to the paper properly.  The result is fantastic, especially for the really big traces on the motherboard:

In reading online, I also discovered that a lot of people actually fully immersed their transfers in water right after they finished ironing.  So I filled up a large corn roasting pot.  And after 20 minutes of mad ironing, dunked my ‘transferred’ PCB:

And voila!

Now that I’ve got my ‘technique’ sort of down, I can make more of the boards.  With 5 pieces of 200x300m PCB, I’ll make two mainboards, and then on the remaining 3 pieces make 2 each of the cursor, timing and memory boards.

A few days and many sore arms later, here we have it:

Okay.. now I’m getting impatient.  I really want to etch.  Should I just risk it with the muriatic acid?  Hmmm…. 🙂

Have been at a bit of a standstill on etchant.  They don’t sell the stuff anywhere in my town at all, so I have to order online.  It is apparently possible to mix your own using muriatic acid and peroxide; however, remembering my experiences with that nasty  acid cleaning our old concrete pool, I wasn’t eager to risk burns and who knew what else messing with that stuff.

Anyway, let’s focus on what we can do – the latest boards from China finally arrived.  They don’t *look* green to me, but I realize quickly the copper on the one side is distorting the color.  I decide I might as well proceed to the ‘design’ stage and start figuring out how to create the patterns I’ll need to etch with these.

I did consult pretty widely.  Most suggested using PCB cad software to recreate the boards.  I had the original plans via Michael Holley’s SWTPC site, but the low-res scans he’d made available weren’t that great and I was told I’d have problems with broken traces, etc as a result.  Still, I really wanted to use the original artwork.   I mean, yeah, going the redesign route would allow me to produce better quality boards and fix known issues with the originals in advance; but to me that meant going away from the whole purpose of the project.  There was something about using original artwork that just made the thing feel more authentic.

Here’s a sample of the artwork:

http://www.swtpc.com/mholley/TV_Typewriter/page_22.pdf

You can see the problem right away.. the scan produced fades on some of the traces.  That’s going to make it difficult or impossible to avoid etching those away.  But, this is 2016, and we do have this thing called Photoshop.  So let’s see what we can do with these.

First, we need to convert them from PDF into a format Photoshop can use, like JPG.  I downloaded the individual files from SWTPC.com and then used this free online pdf to jpg converter, set at 300dpi to do the conversion.  I then downloaded the resulting jpg files and opened them in Photoshop.  I started with the timing board.  First order of business, cut out the parts placement page.

Next thing we have to do is get it scaled correctly.  There was no scale offered; the magazine of course wasn’t accounting for vintage computer enthusiasts in 2016 downloading these in scanned PDF format.  They assumed you’d have the originals, in which case they’d be at their ‘full’, correct size.

I started by printing as is, placing my ICs at various locations to see if the pins fit, and then using Photoshop’s Image Size tool to increase the size until things fit, making sure to keep proportions the same.  Eventually I got a width of about 8.247 inches and a length just a hair under 11 inches.  Keeping that info in my back pocket, I now knew what I had to size all the other artwork plans to.

The next thing we need to do is ‘fix’ the artwork.  First, I stripped it of color, making it a pure grayscale image.  Through google, I learned of a tool called ‘threshold’ that allowed you to eliminate greys.

Moving the slider to the right, to about 172, created an amazing improvement in the darkness of the traces.  Had to kind of play with it a bit more to get it as close to ‘just right’ as possible — too far in one direction and it eliminates all the drill holes, too far in the other and traces white out completely.

I had only ordered five of the green-looking Chinese FR4 boards, but I realized because of their size (200mm x 300mm), that was actually all I’d need to create two sets of boards.  Of course, this being my first time, I was probably going to fail miserably on the first attempts, so probably not.

Anyway, for the smaller boards, I decided to put two per sheet.

Now, you’ll note I did one final adjustment — I flipped them horizontally.  This is because along the way, I decided I would use the modern ‘toner transfer method’ of PCB making.  Based on reading, it just seemed like the easiest way to get the job done – a splash of modern that nobody would care about, as long as the boards ended up looking correct.

Back in the day, you might have taken these plans, had them printed as-is onto transparencies, and then placed those transparencies over the pre-sensitized PCBs in order to expose them and remove the protection on the copper you didn’t want to keep.  Because you’re using a transparency, you can leave the orientation as is and it’ll be correct.  However, toner transfer is different.  You’re printing onto a medium (ie magazine paper), and then you’re placing that down on the board and trying to, via heat and pressure, force the toner to jump over to the copper on the board.  If you just print the patterns as is, the resulting pattern you iron onto the board will be backwards.  So you have to mirror image it before printing.

Now that I had that, the next step was what to use to print it.