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Tips for cutting ventilation slots in a PAC-10 case?


fussylizard

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Print some parallel lines on paper, alternating 2.5mm and 3.5mm widths... i.e. you are trying to make the slots 2.5mm wide with 3.5mm between them.

Sticky tape the paper over the place you want the slots, especially as it curves to the bottom.

Use a sharp craft knife to score through the lines of the paper and into the case.

Remove paper.

CAREFULLY use a Dremel and grinding disc to cut a narrow slot. Note the plastic melts as you do this, but you can wait for it to cool and harden and then scrape it off. Go slowly. Don't go all the way to the ends of the slot. You really just want enough to get a craft knife into the slot. Alternately, use 2mm drill bit.

(This is the way I did it last - next time I might try something other than a grinding disc, like some other metal Dremel drilling/routing bit or a metal disc).

Clean up the inner edge with a sharp craft knife. Use knife to carve out the ends of the slot neatly.

Use an emery board to sand edge down to the score line.

Since you made the slots 2.5mm wide, it's now OK to sand down a little bit extra and you'll end up with 3mm wide slots separated by 3mm.

The sanded edge is going to be matte and not as black, so fix it up with a black Sharpie.

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  • 5 weeks later...

I cut ventilation holes today!  It went quite smoothly actually.  Not sure how helpful this will be for others since I used a small milling machine to do this (instead of Wilba's Dremel-based approach), but I figured I'd document it for future reference anyway.

I used a 1/8" end mill to make the cuts (first pic).  End mills look similar to drill bits but drill bits are designed to cut down (to create a hole), whereas end mills are designed to cut from the side.

First I used a ruler to mark five lines 1/4" apart to mark the middle of each of five slots.  I also drew a line parallel to the edge of the case where the vent slits would be cut (so I would know how far into the side of the case to cut, and so each slit would be cut into the side the same distance).  (Second pic; the parallel line is a bit feint, but it runs just below the five marks).

Next I clamped the base part of the case upside down onto the milling table (third pic).  Since the top side of the case is sloped I had to prop it up so that the slits would be perpendicular to the bottom once I flipped it back over.  I also set the depth stop on the mill so that all the cuts would be the same depth (1/2" from the bottom).  Once everything was lined up for the first hole I set the mill on a slow speed so I wouldn't melt the plastic (probably ~200 RPM).  Once each slot was cut, I finished up the slot at probably 800 RPM (just to take off any remaining material).  The fourth pic shows the first slot being cut.

Continued in next post...

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The first pic shows the result after the fifth slot was cut.  Notice that the left edge of each slot is nice and clean since it was cut by the leading edge of the tool (which was moving clockwise), whereas the right edges look pretty rough.  I unclamped everything and was pleasantly surprised that I could just scrape off the junk on the trailing edge with my fingernail.  I used the back of an X-acto blade to scrape the final stubborn bits off, but I didn't actually have to do any cutting.

The second pic and third pics show the final result.  I'm really happy with the result and it was relatively easy.  Pity it requires a milling machine and associated tooling to use this method, but if you have access to the tools, I highly recommend it...

N.B. Those are not the final knobs...

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You mean you can actually use this thing to make music?  I thought it was all about the soldering and the flashing lights! :-)

I've just barely scratched the surface of it, and man, the MB-6582 is a destroyer.  That "fat pulse" sound from the "first steps" section of the guide with just two SIDs is huge.  I've been overwhelmed by the sound of it, it's just fantastic.  I finally got around to uploading the vintage 2 presets and had some fun with that, esp. the drum sequences.

Hats off to TK for the whole concept, and to Wilba and SmashTV for making it easy to build with designs, docs, and parts.  Well done guys!

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