shielding enclosure for prototyping

Construction information for DIY projects, including the MS Mid Side Matrix, Elliptic Equalizer, Mastering Console, Phono Transfer System, Insert Switcher and the Dual Class-A Amplifier. You can post your baby pictures here.
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brianroth
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shielding enclosure for prototyping

Post by brianroth » Sat May 18, 2019 8:31 pm

Now this is turning into "over thinking" for me....lol

Recent threads here about the phono preamp and noise abatement for measurements stirred up months/years ago memories.

Recent discussions also involved using pots and pans from the kitchen for shielding!

Back to my earlier thoughts. Find a decent sized metal box with a cover plate. Poke holes on one end of the box for some XLR's and TRS jacks, as well as some binding posts for power supply. Inside of the box, break out those connectors onto Phoenix screw terminal blocks.

Concept is the ability to stuff a solderless breadboard or a "crackerboard" proto or an actual PCB proto into a shielded enclosure with I/O connections into the rest of the test bench.

I had thought about using a Hammond cast AL box (specs hopefully linked later in this missive), but after Wayne's comments recently, I'm now pondering use of a 10" x 10" x 4" NEMA screw cover pull box because the 16 ga steel should also add some magnetic shielding.

In either case, use the powder coated version for a bit of minimal protection against short circuits inside the box, and concoct a plastic insulator in the floor of the box for better protection against wire nubs stabbing into the bottom of the metal box.

Comments?

Bri
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mediatechnology
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Re: shielding enclosure for prototyping

Post by mediatechnology » Sun May 19, 2019 6:00 am

I need to try one of those. Thanks for posting it Brian.

I had to shield a transformer which was about 35 mG the other day for a client and it looks like mu-metal will be about the only thing that works. For the phono preamp, which is seeing 1-2 mG steel may be good enough.
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Re: shielding enclosure for prototyping

Post by brianroth » Wed May 22, 2019 10:14 pm

For many years, I've used the the steel NEMA boxes to house custom power supplies, typically with Power-One/whatever "open frame linear" modules mounted inside. In a few cases, I even bolted the NEMA box onto a 19" blank plate so the assembly could be rack mounted.

Hmmmmm...no pix of the bigger builds are handy here, but I found a pic of a pair of smaller boxes which were built to power a few Trident 80B modules intended to be used as an outboard.

Bri
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brianroth
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Re: shielding enclosure for prototyping

Post by brianroth » Wed May 22, 2019 10:26 pm

Onwards to my research. I dunno if I can post all this into one email. If not, then followups.

First is my collection of part numbers. If all goes well, then catalog pages/cut sheets.

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mediatechnology
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Re: shielding enclosure for prototyping

Post by mediatechnology » Thu May 23, 2019 9:41 am

Brian - Those look very neat and tidy. The heavy gauge steel is a real benefit for carrying the weight of the power transformer.

Just checked Home Depot and a 6x6x4" 16G is only $18.45. The default store had >10 in stock.

I've seen smaller toroidal transformers mounted in quad outlet boxes or ceiling fixture boxes as well.
IIRC one was bolted onto the back of a Heathkit IG-18 oscillator.
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Gold
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Re: shielding enclosure for prototyping

Post by Gold » Thu May 23, 2019 10:15 am

I’ve been thinking about how to make custom enclosures efficiently and relatively quickly. My basic plan is to make a frame with end pieces to mount controlls and connectors. Each end would be aluminum and would be connected by pieces of bar stock at each corner. Then bend 400 series stainless steel over the frame. I think the basic concept will work but there are some construction details to be worked out.

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Re: shielding enclosure for prototyping

Post by brianroth » Fri May 24, 2019 8:50 pm

Wayne, I'm almost certain that the boxes shown in my Trident module PSU pics (shown above) were 6x6x4, but purchased here in Salina from one of the local electrical jobber houses. I do recall buying some of those from Home Depot when I lived in OKC. Alas, no Depot here....Lowes and Menard's (which is a pretty kewl Big Box store).

Thinking back many years:

Mid 1990's: Someone broke into a nightclub and stole some racks with outboards and the desk PSU. The desk might have been a Wheatstone....faded memories. Replacement PSU not available. I bought some hefty Power-One open frame linears, stuck them in a big-ass
Hoffman box and used "hardened/SAE" 1/4 x 20 bolts to secure the box onto a steel rack panel.

Late 1990's: Client/friend bought a Neotek Series??? recording desk which came with a Bullcrap DIY PSU. Again, stuffed some Power-Ones into a Hoffman, but that one sat on the floor near to the desk.

No pictures....before I bought my Canon digicam, and YEARS before cell phones had useful cams. (Some of us recall 35mm film cams and sending out the film for processing...a PITA!!! lol)

Silly question now...HOW do desks get separated from the OEM supplies (which to be honest, often times sucked) , or the original service manuals??????

Bri
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