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Old 4th June 2013, 05:58 PM   #11
srinath is offline srinath  United States
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And 3003 -
3003 Aluminum Alloy contains Manganese as its major alloying element. 3003 Aluminum is an alloy with very good corrosion resistance and moderate strength. It is not heat treatable and develops strengthening from cold working only. 3003 Aluminum Alloy has good machinability and welding is readily accomplished by means of conventional welding methods. Commonly used in chemical equipment, ductwork, and in general sheet metal work. 3003 Aluminum is typically used in stampings and the manufacturing of pressure vessels, builder's hardware, garage doors, awning slats, refrigerator panels, gas lines, gasoline tanks, heat exchangers, drawn and spun parts, and storage tanks. All of our 3003 Aluminum Sheet is protected on one side with a protective vinyl film.

And 5052 -

5052 is an aluminium alloy, primarily alloyed with magnesium and chromium. It has good workability, medium static strength, high fatigue strength, good weldability, and very good corrosion resistance, especially in marine atmospheres. It also has the low density and excellent thermal conductivity common to all aluminium alloys. It is commonly used in sheet, plate and tube form.
Typical applications include architecture, general sheet metal work, heat exchangers.

No reason you'd want either of these 2 over 60/70. You're not doing duct work inside your amp are you ? Then no.

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Srinath.
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Old 4th June 2013, 07:20 PM   #12
WagBoss is offline WagBoss  Canada
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Quote:
Originally Posted by dirkwright View Post
One question you need to ask yourself is do you want it to work as an RFI and EMI shield for your circuit? Another question is do you want to minimize the number of tools you need to make it?
I don't know, do I? I have lots of tools so I don't know, I'm going to get the aluminum off here probably METAL SUPERMARKETS - Buy Metal Online - Small Quantity Orders for Aluminum, Stainless Steel, Hot Rolled Steel, Cold Rolled Steel for Delivery or Local Pickup so what do I need to attach a bunch of different rectangles together, to make it look nice?
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Old 4th June 2013, 07:30 PM   #13
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Quote:
Originally Posted by WagBoss View Post
I don't know, do I? I have lots of tools so I don't know, I'm going to get the aluminum off here probably METAL SUPERMARKETS - Buy Metal Online - Small Quantity Orders for Aluminum, Stainless Steel, Hot Rolled Steel, Cold Rolled Steel for Delivery or Local Pickup so what do I need to attach a bunch of different rectangles together, to make it look nice?
Unless you want your circuit to oscillate, then I'd recommend a box that performs well in rejecting RFI and EMI. I can't find any specific guides on designing a good box, from what I've seen, there is usually a good overlap at each junction of the box.

If you don't want to buy a sheet metal brake, then you can use angle and rivet or screw them together. I buy from these guys:
http://www.speedymetals.com/
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Old 4th June 2013, 08:02 PM   #14
srinath is offline srinath  United States
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What I have ended up with in my quest for a case for my tas5630 amp is a pioneer ct2121 casette deck chassis. Or the nearest dead vintage casette deck chassis. Or CD player, or VCR or any thing else in that family.

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Old 4th June 2013, 08:10 PM   #15
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One requirement of chassis that shields from RFI and EMI is that all panels must be electrically connected together and grounded. This means that your fancy looking black anodized case is really a piece of crap when it comes to shielding RFI. Anodizing is not electrically conductive! Try it yourself. Set your DMM to "continuity" and put the probes on the anodized surface. You will see that it does not conduct. So, unless there is a separate ground wire bonded to each anodized panel, you'd might as well have no chassis at all. Bare aluminum is fine, as is alodined aluminum. You also can't have substantial holes in the case if you want it to function as a shield. You can use a special screen in larger holes to keep RFI out, but of course it has to be bonded to the chassis and to ground to function.

Last edited by dirkwright; 4th June 2013 at 08:14 PM.
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Old 4th June 2013, 08:28 PM   #16
WagBoss is offline WagBoss  Canada
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ok the RFI and EMI won't be a problem I basically will just have a solid aluminum box, no anodized.
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Old 4th June 2013, 08:30 PM   #17
srinath is offline srinath  United States
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I thought steel was better to sheild. That's why transformer covers etc exist and are made of steel.

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Old 4th June 2013, 08:35 PM   #18
WagBoss is offline WagBoss  Canada
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So what I'm planning now is Top, bottom, side, side, back all 0.063 inches/(16 gage)/1.5mm and then I'll get like a 1/4" thick front plate. I will attach them together with angles. Is there anything else I need to buy to do this other than angles and the sheets?
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Old 4th June 2013, 08:36 PM   #19
WagBoss is offline WagBoss  Canada
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Quote:
Originally Posted by srinath View Post
I thought steel was better to sheild. That's why transformer covers etc exist and are made of steel.

Cool.
Srinath.
Should I make it out of steel? I figured aluminum was better that's what I always see.
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Old 4th June 2013, 09:10 PM   #20
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Quote:
Originally Posted by WagBoss View Post
what grade aluminum? I want to brush it. I can get:

2024T3
3003H14
5052H32
6061T6
7075T6
It is wonderful when folks without a clue offer advice.

2024T3 is the old aircraft standard for aluminum. Today it is used mostly for keys. It will polish up quite nicely.

3003H14 is crap. It is the cheapest sheet aluminum and is usually sold in rolls. Useful for flashing and decorative uses. The lowest strength on the list.

5052H32 is the standard for sheet metal use. It forms well but does form small cracks on tight bends. it is the material of choice for decent quality sheet metal.

6061T6 is the work horse of aluminum alloys. It welds well is decent at machining, but a bit gummy, so use a lubricant such as Tap-free for aluminum to keep it from sticking to your tool bits and slowing things up.

7075T6 is the stuff they really build airplane parts out of. It is the strongest and most expensive. It with a bit of effort will take a shine and look like chrome.

So use either 5052 or 6061.

Anodizing is a nice way to finish aluminum. If you are bolting the pieces you can use a bit of lye in water to remove the anodizing where you want electrical contact.

There are other finishing processes that leave a conductive surface, but they are not very common these days and a bit expensive.

The easiest way is to use an aluminum top plate and wood sides.

RFI is a problem with bipolar junction transistors, not so much tubes or FETs.

For a 19" panel 1/8" is the minimum thickness for looks 3/16" or 1/4" is better. 1/16 or .062 is fine for small chassis, but for larger ones or to support a heavy transformer go for .080." or there abouts.

Steel is a bad idea. You can actually measure the distortion introduced into an audio signal line when it is routed close to a steel chassis.

ES
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