synkrotron wrote: ↑
Mon May 25, 2020 4:22 pm
Impressive sounding filter
And an impressive build too. I'll check out through this post to find out how you get those great looking front panels.
I am pretty green when it comes to this kind of stuff. So I am not familiar with the Intellijel unit.
Thanks for all the kind words, Andy!
The panel was made thus:
I have my local "Metal Supermarket" in Richmond, BC cut an 8.75" strip off the end of a sheet of 0.080" thick aluminum 6061, then cut that 4' long strip into a number of pieces of width 7" (4U), 5.25" (3U), 3.5" (2U) and 1.75" (1U), calculating the total to minimize waste. The cost is about $2 per U. This particular build used a 3U panel blank.
Next, I design the front panel on Front Panel Designer, which is a free software that you can download from Front Panel Express. I set up the panel as if it were to be powder-coated in Traffic White. I create a User Grid in the program to 0.1" and place all components (which are basically just holes) on that grid. That makes it a snap to lay out the Panel PCB in Excel later. Then, after the entire panel is exactly the way I want it, I group everything together and mirror it horizontally relative to the middle of the panel. This creates a mirror image of the panel for printing.
Next, I print the panel out on standard Lazertran paper for laserjet printers. First I cut the Lazertran to the width I need, taking care to minimize waste (cuz that shit's expensive! -- like $3 or $4 per sheet). I tape the Lazertran strip onto the middle of a piece of standard letter paper and place it on the top of the paper tray. Then I print the panel onto the Lazertran backwards (mirror-imaged). This is because when you bake the Lazertran onto the panel blank, you want the printed graphics to be between the plastic sheet and the metal, and not on top of the sheet. This renders the graphics more or less indestructible.
The next step after printing is to go over the entire printed Lazertran sheet thoroughly with a hot air gun (which is like a hair dryer on steroids), being careful not to actually melt the Lazertran, but coming damn close. This step is very important. Failure to do this step will give you bubbly messed up graphics on the finished panel (learned that the hard way).
Next, I thoroughly clean the business side of the panel blank with soap and water. Some people sand the panel, but I like to leave the original finish intact. Usually, the metal sheet will have a protective sticker on it, which needs to be peeled off. Any residual adhesive from the sticker should first be removed with acetone before giving the panel its final wash. Once the panel is thoroughly washed and rinsed (and any rough edges smoothed with steel wool), I submerge it into a tub of tap water.
Next, put the printed and heat-treated Lazertran sheet into the water. It will curl up into a tube. Let it sit in the water for a couple of minutes. Then carefully unfurl it, place it printed side down on the panel blank and very gently and carefully remove the wet paper backing, leaving the very delicate 15-micron thick plastic sheet on the panel blank. Then remove the panel from the water, very carefully slide the Lazertran plastic into its final position (the corner mounting holes help with this), put it under running tap water and use your index finger to gently rub all over the plastic, which squeegees it down and also rubs the Lazertran adhesive off of the plastic (remember, we are applying the Lazertran upsidedown, and it has an adhesive backing which must be rubbed off, or it turns brown during baking) and finally use a silicone kitchen spatula to gently squeegee the water from underneath the plastic. After the Lazertran is firmly down on the aluminum, I gently dry it with a folded up paper towl.
Now comes the tricky part -- baking. This is the part which must be done perfectly right. Here's what I do. I have a small Kitchen Aid toaster oven:
which I bought second-hand for $75. I use this for my panel bakes. First, I turn it on and set it to Bake and Warm with the oven door open. I place the panel on the middle rack and cover it with the baking pan upside-down. I don't expose the panel directly to the heating element of the oven. Then I bake for 20 minutes on Warm with the oven door open. This is just to gently dry the panel. Here is the baking schedule I use:
20 minutes: Warm with oven door open
20 minutes: Warm with oven door closed
20 minutes: 200F
20 minutes: 250F
20 minutes: 300F
20 minutes: 350F
20 minutes: 400F
Turn oven off and open door. Let panel cool in oven for an hour.
So, the entire bake takes 2 hours and 20 minutes, plus an hour for cooling. I have found, by trial and much error, that this is the magic formula for getting perfect baked-on Lazertran panels. The first 20 minutes with the oven door open is the most important thing. If the oven door is closed right away, the panel will get too hot before it is completely dry and will not turn out very well. I try to organize things so that I have other stuff to do in Sketchy Lab while the panel is baking. Since the oven is in Sketchy Lab, and I'm timing it on my phone, I can sit there and solder circuits and shit, getting up every 20 minutes to adjust the oven. I never look at the panel while its baking -- wouldn't want to jinx it!
After the panel is baked and cool, it must be drilled. The first thing I do is sit down at my bench with a small hammer and a centre punch, and I punch small divots into the centre of each component hole. I just do this by eyeballing it -- it's close enough. Then I use a 1/8" drill bit to drill a small guide divot on each hole, using the centre punched holes as guides. These little 1/8" divots guide the larger drill bits. This step is very important for getting precision hole placements.
For components, I use 1/8" for 3mm LEDs, 3/16" for corner mounting holes, 1/4" for toggle switches, and 3/8" for both Switchcraft jacks and those nice PCB-mounted 12-mm Alpha pots I get from Small Bear. If I use 24-mm non-PCB-mounted Alpha pots, I use 5/16" for those. I also deburr both the fronts and backs of each hole. For the 1/8" holes I use the 3/16" bit to very carefully deburr. For the larger holes I use the deburring tool:
This gives nice holes with no rough edges.
So, basically, this is a 5U version of the Intellijel Dr. Octature II (which has been discontinued, along with most of my original designs). Here is a decent little video:
I designed all of the Intellijel filters -- Dr. Octature (and Atlantis), Korgasmatron (and Morgasmatron), uVCF, and Polaris. Of all these, Dr. Octature is still my favorite, for general creaminess and four-pole goodness.
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