[sdiy] PCB size for euro-rack format

[Laurie Biddulph]

I think you will find the Eurorack systems like Doepfer are the smallest 
with Frack rack being a fraction bigger in the useable panel area. 3U is 3U 
(133.4mm) no matter what system you use. The available space on a panle is 
dictated fundamentally by the mounting mechanism. In the Doepfer systems the 
fixing holes are 3mm in from the top and bottom edges of the panel which is 
128.5mm high. Assuming symmetricality, that means 12mm is removed in total 
from the panel giving 116.5 (so we will go for 115mm as a round number).

A 115mm pcb will not fit into a Eurorack system that has card guides in it. 
Although not used in the synth world (AFAIK) they offer stability and 
support to any module. So a 115mm pcb will NOT be universal. A 100mm pcb 
WILL be universal.

True, the racking standards work on the shortest depth being 160mm (which is 
why a Euroboard is 100mm x 160mm) but racks can be 220mm and deeper. 
HOWEVER, a 160mm deep board IS universal in the racking industry but not in 
the SYNTH-RACK industry. The Doepfer cases will not accept 160mm deep 
boards, they accept 100mm in most areas but only 85mm in front of the power 
supply. If you were to go for a TRULY universal pcb then it would surely 
have to be 100mm high and 85mm deep......

If I have it right, the Fracrack allows the panel to extend to the top and 
bottom edges of the case so they have an initial panel height of 133mm. from 
that you have to deduct the thickness of the 2 rails and you get, I believe, 
slightly more panel space to work with.

PS when referring to panel space I am actually referring to the space on the 
back of the panel where the components will be mounted. Items such as pots 
require more panel space than switches and a pot cannot extend in to the 
rail area or beyond the edge of the panel. In principle, Frackrack and 
eurorack have almost the same amount of `printable' panel space on the front 
but differing `working' space behind.

Best Regards

(Mr) Laurie Biddulph
Phone: +61 (0)2 4340 0938
Mobile: 0400 257 645

Elby Designs
ABN: 70 022 727 605
http://www.elby-designs.com

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----- Original Message ----- 
From: "Andre Majorel" <aym-htnys at teaser.fr>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, November 29, 2008 6:56 PM
Subject: Re: [sdiy] PCB size for euro-rack format


> On 2008-11-29 01:25 +0000, Seb Francis wrote:
>
>> I want to make a PCB compatible with a wide range of modular
>> formats. Assuming euro-rack to be the smallest, what height
>> would my PCB need to be?
>
> On mine, the clearance is 112 mm. But the smallest format is not
> euro-rack, it's frac rack. According to Tom Bugs and Dave
> Magnuson, height and depth are 4.25" x 7" for PAIA and 4.125" x
> 6.875" for Blacet.
>
>> I'm thinking 105mm, but I'm not really sure of the different
>> case options out there. The depth will have to be as big as it
>> needs to be  to fit everything on, but it would be useful to
>> know a typical max depth if such a specification exists.
>
> Euro-rack frames come in several depths but I think they're
> guaranteed to be deep enough to hold a 100 x 160 mm PCB and a DIN
> 41612 backplane.
>
> -- 
> André Majorel <URL:http://www.teaser.fr/~amajorel/>
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