Mounting frame

I took the Scotty’s advice of building everything into a large blank PCB.  You cut holes in the board in exactly the same size as each panel.  When you’re ready to install a module, you solder a few spots around the perimeter.  These hold the module in mechanically and help ensure a solid ground.  Later, when I’m sure it’s working in concert with everything else, I’ll solder on a fence to isolate everything.  To make the frame, I decided to design a graphic from the layout image above and iron-transfer it to the PCB.  After, I’d use that as a guide for cutting out the holes.

First (failed) attempt

My first attempt was simply mirroring and printing the diagram as it was.  The lines were relatively thin, and I don’t think there was enough toner to really grip.  Also, I was figuring out the other day how long it had been since I attempted a toner transfer…  it’s been about 4 years, so I’m a little out of practice.

Cutout guide (click for PDF)

After another failed attempt, I decided to make the background black and the modules white so there was plenty of toner to bond to the PCB, and I can extend and estimate where the border is.  This worked much better, though there were still many holes.  I’m not really sure what I’m doing different.  I couldn’t find my old stash of glossy photo paper, so I tried Kodak paper for the first try (bad results).  My friend suggested using a page from a magazine (about the same as the Kodak paper).  The “good enough” result was using the updated image and magazine paper.

Finally good enough.

Using this extra information, I filled in some of the gaps with sharpie and headed out to the shop.  I made corner holes for each module hole, and tried to cut the flats with a coping saw.  While I finished a few that way, it was a painful and slow-going.  Later, I used the dremel again with a carbide milling bit.  This method went very quickly , though there was more wavering in the final cut.  I cleaned each of the holes with sandpaper and enlarged them enough for the modules to have a mostly tight fit.

Cleaning the frame

Once I finished making and refining the holes, I cleaned-off the toner.  After the toner was all cleaned-off, I soldered the entire surface.  It took forever, but I needed to make sure that it didn’t oxidize, preventing soldering later.  With the entire surface “tinned” I put it in the toaster oven to smooth everything out.

Master Oscillator mounted

While in the toaster, the bottom side of the board, which I’m not going to solder on, developed a pretty oxide layer.  In the above photo, I have the master oscillator installed.  I’m still not totally sure if it’s 100%, and I still need to solder on one more connection to it, but once those things are taken care of, I’ll solder on a cover.

  1. #1 by LB3HC, Marius on February 10, 2012 - 11:53 am

    Hi. Nice work. Please be adviced that the dust from FR4 printed circuit boards may not be good for your lungs if you breathe it. Be careful when you work with milling FR4 and all fiberglass products that emits fine particle dust.

    73
    LB3HC

  2. #2 by Chris on September 1, 2012 - 5:31 pm

    I second Marius’s opinion. When you are doing anything with fiberglass you should have the best dust control you can afford and also wear a P100 level mask.. (the purple cartridges), you only have one set of lungs. They still are not admitting how much fiberglass can hurt people because its a BIG problem. But its real.

    Also, wipe everything near your setup down afterward with a damp cloth and rinse it out..

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