Tapping has always been hit and miss for me, and I hope the guide will make my success
much more consistent.
Thanks, Tom. I've just Prichard some Tap Magic, so hopefully it will do the trick. I've also used WD-40 in the past, which actually works well for drilling aluminum. We'll see how they compare.Another must-have is cutting fluid. Supposedly water can work with aluminum but it causes your tools to rust. In the past I've used denatured alcohol (ethanol). These days I use A-9 Aluminum Cutting Fluid (not to be confused with A-1 steak sauce).
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Tom
I've just created the drilling template for the back panel. It's a bit narrower than the actual panel, which is fine for me to tape it on. I'll use a punch to mark the centers of each hole and six "corners" of the IEC C13 socket.
- I've got a 24mm knockout punch that works really well for the various Neutrik connectors along the top.
- I'll use a half-inch bit to drill the holes for the Keystone binding posts and fuse holder in the middle row.
- I'm going to try the IEC socket using a Dremel with a cutting disc. In the past I drilled starter holes, followed by a jigsaw, but I was never happy with the result. We'll see if the Dremel works better. I've also heard a coping saw can do the trick.
Most IEC inlets - including the Bulgin PF0001/xx that I like - can drop into a rectangular cutout as long as the corner radius is reasonable (check the data sheet for the inlet). They usually leave a fair amount of overlap from the edge of the cutout to the edge of the connector, which allows you to hide imperfections as long as you mount the connector from the outside of the panel. It's really only if you mount the connector from the inside that the cutout has to be perfect ... or if you're a perfectionist.
Drilling 0.5" holes in sheet aluminum can be tricky. Carbide tipped hole saws are quite affordable at Bezos' Bookstore. I have one for drilling 24 mm holes and it works great! A stepped drill bit can be another option.
Tom
Drilling 0.5" holes in sheet aluminum can be tricky. Carbide tipped hole saws are quite affordable at Bezos' Bookstore. I have one for drilling 24 mm holes and it works great! A stepped drill bit can be another option.
Tom
Hi Mike, I'd be particularly interested in how you make out with that Dremel, so I'm wishing you the best of luck and hoping to see your report.
I ended up using a Diamond Wire Saw, and it worked quite well. Just a bit of filing after resulted in a fairly clean and snug fit.
Depending on the panel thickness a regular coping saw can work too. Use the finest toothed blade that you can find. I bet the diamond wire is even better, though.
I generally drill a bunch of small holes just inside of the cutout. Then I punch out the centre and file to the edge that I want. It's annoying work but I can usually make a hole for an IEC inlet in maybe 15-20 minutes. One drawback is that the drill bit tends to wander a bit unless you centre punch, which I don't as I'll be filing anyway. That can make it a bit difficult to get the centre out of the cutout. I've often wondered if a centre drill would be better.
Tom
I generally drill a bunch of small holes just inside of the cutout. Then I punch out the centre and file to the edge that I want. It's annoying work but I can usually make a hole for an IEC inlet in maybe 15-20 minutes. One drawback is that the drill bit tends to wander a bit unless you centre punch, which I don't as I'll be filing anyway. That can make it a bit difficult to get the centre out of the cutout. I've often wondered if a centre drill would be better.
Tom
Drilling plus diamond wire…sounds like a plan and maybe even a useful skill. Thanks, Tom and Mike. 🙂
I'm making progress. I started with the rear plate, drilling the ½" holes for the fuse holder and Keystone binding posts, and the pilot holes for the Neutrik connectors and IEC power input. After finishing the IEC hole, I started to use the 24mm knockout punch to do the Neutrik holes, and promptly stripped the punch. It was cheap, so I've ordered another (two). Unfortunately, it's going to take 1-3 weeks to arrive.
I've proceeded on with the base plate, drilling all the holes for the Intelligent Soft Start, two Power-686, and two transformers, plus three chassis grounding holes (with sanding), and four holes for the feet. I've just finished putting all that together:
I just noticed that the left transformer needs to be rotated 90°CCW. From what I understand, toroids are good at minimizing EMI, but they have a bit of "turbulence" at the wire exit points. Therefore, I'm trying to aim those two points away from the Modulus-686 units, which will be sitting quite close to the transformers.
Additionally, the preferred position for the transformers has them mounted to the "grill" area of the Dissipante, and I'm concerned about the strength of those little slats. I had an old 1mm steel plate from an earlier Modushop Pesante build, so I hacked a couple of chunks off to use as large washers to spread the force over a wider area. That should improve vertical strength, but the horizontal strength still depends on two little grill slats, which were lessened further to make way for the bolt hole. Consequently, I'll probably use some epoxy to affix the "washer plate" to the bottom, and I might even fill the grill gaps to solidify it further. That should help with horizontal stresses.
Finally, the front feet are near the corners (hidden behind the transformers), but the rear feet are a fair distance from the back. Here's my thinking:
I've proceeded on with the base plate, drilling all the holes for the Intelligent Soft Start, two Power-686, and two transformers, plus three chassis grounding holes (with sanding), and four holes for the feet. I've just finished putting all that together:
I just noticed that the left transformer needs to be rotated 90°CCW. From what I understand, toroids are good at minimizing EMI, but they have a bit of "turbulence" at the wire exit points. Therefore, I'm trying to aim those two points away from the Modulus-686 units, which will be sitting quite close to the transformers.
Additionally, the preferred position for the transformers has them mounted to the "grill" area of the Dissipante, and I'm concerned about the strength of those little slats. I had an old 1mm steel plate from an earlier Modushop Pesante build, so I hacked a couple of chunks off to use as large washers to spread the force over a wider area. That should improve vertical strength, but the horizontal strength still depends on two little grill slats, which were lessened further to make way for the bolt hole. Consequently, I'll probably use some epoxy to affix the "washer plate" to the bottom, and I might even fill the grill gaps to solidify it further. That should help with horizontal stresses.
Finally, the front feet are near the corners (hidden behind the transformers), but the rear feet are a fair distance from the back. Here's my thinking:
- The case is 400mm deep (front to back), which is larger than any of my shelves. Therefore, I didn't want the feet to extend beyond the reach of a typical 300mm shelf.
- The transformers represent a significant proportion of the weight, so the unit is front heavy. It's never going to tip backwards, because of the shifted position of those rear feet.
- Just for kicks, I may add a fifth foot at the back center, utilizing the grounding hole. The main four are antivibration feet from Modushop, and I don't have a spare of that type. Therefore, I may use some Sorbothane to create a spacer so the non-magical foot ends up at the same height. Or I may just use a normal foot, for sliding the case back into the shelf area, then lift it a bit when the actual rear feet encounter the shelf edge.
All the modules are mounted, including the four in the side heatsinks, and the Dissipante case is mostly assembled:
- The little Guardian-86 mono speaker protectors sited above the Modulus-686 boards are on M3 standoffs. I had intended to tap those into the heatsink, but I accidentally used the drill bit for the M4 taps. Fortunately, I could easily recover by fixing the standoffs in those holes with a bit of epoxy.
- The Modulus-686boards come mounted on heat spreaders that accommodate seven M4 screws.
- I had hoped to bottom tap those, but I didn't have the necessary taps to make it work, so I ended up drilling through and threading the entire hole.
- I managed to break one of my taps, rendering one hole useless. Fortunately holes are closely spaced, so skipping one wasn't a big deal.
- I discovered that in spite of what I've read, WD-40 doesn't work half as well as Tap Magic (for both tapping and drilling).
- For thermal paste, I decided to use some new stuff from Tech Ingredients.
- I've added a toggle switch to the back panel. It's double-throw, like the LED pushbutton switch in the front panel. I'm connecting them in a 3-way configuration along with the switching circuit in the Intelligent Soft Start, so that the amp can be turned on from the front or the back. If this unit ends up at my friend's place, he has his amp tucked behind his TV, and reaching the front switch is a hassle.
- None of the Neutrik connectors are mounted yet, as I stripped the threads on my 24mm knockout punch, and the replacement hasn't arrived. Fortunately all those connections can wait until the end of the wiring job. I can proceed with wiring and testing the power supply, switches, and switch LED in the meantime.
Oh yeah... the IEC C14 power inlet connector that I used initially was quite cheap, so I decided to upgrade slightly to a Schurter 6100.3200.32. This required a bit more filing of the hole, as the new connector was slightly chunkier than the last. Consequently, the slightly ragged hole is a bit tidier.
I had a bit of spare time, so I’ve hooked up the two transformers between the ISS and their Power-686 modules. With my mains at 124VAC, I’m getting ±32.5VDC from the 2x22VAC secondaries of the AnTek AS-4222. I choose the lower 22VAC, because I was concerned about my high mains, but I’ve never seen them hit 125VAC. Given the Modulus-686 can take ±36VDC, I could have probably gone for a transformer with 2x24VAC secondaries. I don’t expect to drive this amp to its max output, though, so ±32.5 should be sufficient.
This evening I'll wire the power supplies to the Modulus-686 boards, and then the amp outputs into the Guardian-86 Speaker Protectors. After that I'll switch over to building the quasi-balanced interconnects, while I wait for the replacement knockout punch for the Neutrik connector holes.
- I twisted all of the transformer wire pairs, then did minimal trimming to get the paired wires even.
- I used ferules to keep the strands together. I had to remove the ferules' plastic shoulders for the doubled primary wires, because the bulky insulation from two wires wouldn't fit. I added heat shrink to those.
- I used spiral wrap to keep pairs of pairs neat and tidy.
This evening I'll wire the power supplies to the Modulus-686 boards, and then the amp outputs into the Guardian-86 Speaker Protectors. After that I'll switch over to building the quasi-balanced interconnects, while I wait for the replacement knockout punch for the Neutrik connector holes.
I built a few amps with the Pesante, but their steel panels made heat dissipation problematic. I started replacing the bottom panel with 3mm aluminum, which enabled me to use them with some of of earlier builds. I eventually just switched over to the Dissipante, even though its heatsinking capacity is overkill for most of my builds.
My advice with the Dissipante:
- Buy a good Phillips screw driver with a really long shaft (>400mm). It makes tightening the front panel screws much simpler.
- Attach rails to side heatsinks, centering them as well as possible. Do this before deciding where to mount things on the heatsink, because the rails often get in the way.
- If you have a 300mm case, then your side heatsinks are in one piece. Just attach the two brackets to each heatsink, using the supplied M4 screws.
- If you have a 400mm case, your side heatsinks will be in two pieces, in which case do this:
- Apply some thermal paste to the end of one heatsink half.
- Lay the heatsink halves on their sides (fins down), with the paste in the middle.
- Loosely attach the steel brackets with the M4 5mm screws (silver panhead).
- Clamp the halves together with some bar clamps, then tighten the screws.
- Drill/thread the heatsink to accommodate your hot stuff. (This is done after, so that you can treat the two halves as a single heatsink.)
- Note that the top and bottom panel have a specific front/back orientation. They snug up behind the front panel, while overhanging beyond the back panel. Line up the screw holes along the rails to determine which is which.
- Drill/punch/cut holes in the base and rear panels. You'll probably mount some or all of the connectors, modules, switches, transformers, feet, etc. before assembling the case. Again, remember that the top and bottom panels have a front and back end.
- Attach the sides to the front plate, with the M4 5mm screws (silver panhead). They should be loose (not even snug).
- Attach the bottom panel using either M3 screws or tapping, depending on your supplied fixings. Again, don't tighten the screws.
- Flip it over.
- Attach the back panel with the black M5 panhead screws and silver nut, again loosely.
- Snug up the screws into the front panel. (Don't tighten them fully, as you may have to loosen them again.)
- Flip it over, then attach the top panel using the same screws as the bottom panel.
- If screw holes don't line up, loosen the screws in the front panel, then wiggle and adjust as necessary.
- Detach and reattach panels as necessary, until everything lines up. If you've been careful as you go, then you may be able to skip this step for the most part.
- Once you're sure things are lining up, you can tighten the screws in the front. I suggest you leave the rest just finger tight, until you're doing final assembly. At that point, ensure that holes are still lining up, then progressively tighten everything.
Thanks, Mike, that’s all especially helpful considering that no instructions are included with the chassis! One additional piece of advice that I would “pay forward”: Beware sharp edges, you can slice yourself badly if you handle some of those pieces carelessly. It might not hurt to dull those edges with a file before anything else.
Especially the steel brackets for the heat sinks can be pretty sharp.
I have Philips head bits for my socket wrench set, so I often just use a long 1/4" extension to reach the screws. Alternatively I swap them out for Torx or socket head types so I can get at them with a ball-end driver.
There's a fair amount of slop in the design of the Dissipante chassis so I leave the heat sink brackets a little loose. I then mount the heat sinks to the front panel and place them such that they are centred vertically on the panel and shows an equal amount of panel on each side. I then tighten the screws and add the bottom panel.
This method does leave a gap between the heat sink bracket and the rear panel. I fill that gap with an M4 flat washer when I attach the rear panel. I use lock washers on the inside. If the "population density" of the rear panel makes it hard to get the washers in, I add a tiny drop of super glue to the washers to hold them in place on the panel while I muck with the screws.
There are many ways to get the job done. As long as you end up with a box in the end life is grand.
Tom
I have Philips head bits for my socket wrench set, so I often just use a long 1/4" extension to reach the screws. Alternatively I swap them out for Torx or socket head types so I can get at them with a ball-end driver.
There's a fair amount of slop in the design of the Dissipante chassis so I leave the heat sink brackets a little loose. I then mount the heat sinks to the front panel and place them such that they are centred vertically on the panel and shows an equal amount of panel on each side. I then tighten the screws and add the bottom panel.
This method does leave a gap between the heat sink bracket and the rear panel. I fill that gap with an M4 flat washer when I attach the rear panel. I use lock washers on the inside. If the "population density" of the rear panel makes it hard to get the washers in, I add a tiny drop of super glue to the washers to hold them in place on the panel while I muck with the screws.
There are many ways to get the job done. As long as you end up with a box in the end life is grand.
Tom