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Old 3rd January 2011, 08:01 AM   #741
massimo is offline massimo  Italy
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Quote:
Originally Posted by merlin2069er View Post
Is that a 2u or 3u case?

I'm looking at a 2u, and the larger caps just fit in the case (it would leave about 10mm room up top).

Oh, one other thing, I thought the 3mm front panels had holes in them for rack mounting?

I'm looking at 2x of 1PS02PN these for my blue dcb1 buffer.

Thanks,
JG
It looks like a HiFi2000 manufactured case. See their e-commerce website: modu
The model is Galaxy Maggiorato (2U) GX 283 or GX288 std version with 3 mm thick alu front panel and mild steel top and bottom panels (also available with 10mm thick alu front panel silver or black and 2mm thick alu top and bottom panels).

RichLund used the alu sides the other way round: the brushed surfaces should be external.
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Old 3rd January 2011, 01:44 PM   #742
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Hi Merlin

The case I used above is the Galaxy Maggiorato GX388 330 x 280 mm with iron covers. The Alu covers look nicer and more expensive but are recommended if you are thinking of heat sinking to the case.

It is 2U - 80mm high.

modushop.biz

There is a 2U rack mounted range for the pesante and slim line models. If you look under spare parts you can order 10mm fronts or alu covers etc.

Massimo - you can use the sides either way round depending how you want the side channel configuration. There are grooves (channels) cut into the sides to allow for various PCB or mounting options. I chose the side with the least grooves on the outside.
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Last edited by RichLund; 3rd January 2011 at 01:48 PM.
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Old 3rd January 2011, 01:57 PM   #743
massimo is offline massimo  Italy
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Quote:
Originally Posted by RichLund View Post
Massimo - you can use the sides either way round depending how you want the side channel configuration. There are grooves (channels) cut into the sides to allow for various PCB or mounting options. I chose the side with the least grooves on the outside.
Of course you can, but they look nicer from the brushed side
Moreover, the two grooves on the (supposed to be) inner side hold M3 bolts, while the other grooves don't. This might be useful to quickly fix some L shaped bars for boards or heatsinking TO220 semis without dirilling holes.
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Old 3rd January 2011, 02:18 PM   #744
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Fair play Massimo I hadn't realised the double grooved sides were for M3 bolt heads, that's a good tip

Certainly using L shaped bars is an excellent way of mounting the boards.
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Old 8th January 2011, 09:35 PM   #745
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I got my isolation pads between my heatsinks and mosfets.

I've checked the test points and get +9.33v/-9.33v
and +9.25/-9.25v on the other unit. So, I believe everything looks a-ok.

Just a couple of questions;

Now that the mosfets are isolated from the heatsinks, I can secure them to the case, right?

What should I do with a/c ground?
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Old 8th January 2011, 09:48 PM   #746
Salas is offline Salas  Greece
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You can drill holes to the sinks and pass bolts to the chassis, or use long Mosfet bolt and extra nuts to secure to both sink and chassis as a system with a single bolt. If you will get any hum, tie a cable from middle point Tx connector to chassis. That is chassis earthing the main PSU return node. You should also tie the mains earth prong at a near point to IEC inlet to chassis anyway for safety. Maybe with a short cable to a ring fastened on one of the IEC female plug's fixing bolts.
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Old 9th January 2011, 06:12 AM   #747
nezbleu is offline nezbleu  Canada
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Default 470 Ohm resistors

Hi:

I am in the process of rounding up parts for a Mesmerize board. The BOM I found says that the 4x470R resistors ought to be carbon film rather than metal film. Can anyone explain this preference? Is there a technical reason why those resistors ought to be noisier, lower precision, or have a worse TCR than the other resistors?

Also, I seem to remember reading something about this in another thread, but can't find it now: has anyone tried using something like buried-zener voltage references instead of strings of LED's? Wouldn't those be quieter, more accurate, better matched, etc? Could they be a drop-in replacement at the current levels used here? Just thinking out loud...

Thanks for any insights.
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Old 9th January 2011, 06:33 AM   #748
Salas is offline Salas  Greece
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Those resistors are gate stoppers. Small enough and of other function than to inflict all those inferiorities you mentioned, but non inductive, which is the major parameter we seek in a stopper. Its almost academic in DCB1's case though because there is plenty of phase margin in the regs to use even the likes of Dale RN60 if you may.

Since you imply LM329 I suppose, those are almost single vendor today and $10 on Ebay to be recommended. If you have them try them. Leds can even superceed them for nVrtHz and harmonic noise when fed from a matching impedance Jfet mind you. Matching for voltage between polarities you will never achieve by the way without a certain mod, because I have already undermined it for total symmetry by design. Only in a Blue Hypno.
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Old 9th January 2011, 08:24 AM   #749
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Carbon comp is non-inductive, but carbon film usually is not, since for values larger than 50 to 100 Ohm the same helical groove construction as with metal film resistors is used to get to higher resistances.
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Old 9th January 2011, 07:37 PM   #750
nezbleu is offline nezbleu  Canada
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Thanks for the responses. There seem to be a few decent carbon composition resistors still in production (or at least still in stock) which I might try. I probably won't bother with the precision voltage refs though.
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