Werner Almesberger werner at openmoko.org
Fri Apr 17 01:41:53 CEST 2009

Joerg Reisenweber wrote:
> Now we are about to discuss how to cram all the stuff already there incl 
> schematics and all into a GTA02 case which never will work anyway

Hmm, I'd say the jury's still out on that one, but it'll be a close
call. The height of the MC75 is a bit of a problem. I just put a stack
of LCM, MC75, and some spacer into a GTA02 case (with the "bumper" at
the bezel) and checked what happened.

- with a spacer of 0.8 mm, everything fit.

- with a spacer of 1.6 mm, I could close the case but it bulged under
  the battery, so the battery wouldn't lie flat when inserted.

- with a spacer of 4.6 mm replacing the MC75 as well, and battery fit
  but it felt as if the LCM was slightly bent.

The MC75 has a nominal thickness of 3.3 +/- 0.3 mm. I measured mine
to be 3.2 mm. Its PCB is nominally 0.95 +/- 0.1 mm.

The stack with the 0.8 mm spacer had a thickness between the inner
side of the battery well and the LCM of about 4 mm:

- MC75 module (3.2 mm), plus
- spacer (0.8 mm), plus
- adhesive tape (negligible)

Thus the results are:

- total stack <= 4.0 mm: everything's okay
- 4.0 <= total stack <= 4.6 mm: the limit is somewhere there
- total stack >= 4.8 mm: clearly too thick

The stacking height for the Molex 53748-0808 connector is 3 mm.

The maximum thickness of the stack would be

- MC75 PCB (<= 0.96 mm), plus
- Plug/receptacle pair (3 mm), plus
- thickness of FPC to connect to the plug (about 0.2 mm), plus
- thickness of solder between FPC and plug (about 0.1 mm)

So the stack would be around 4.3 mm, just about at the upper bound
for what my experiment indicates might fit.

> I'm really puzzled why we (OM that is) don't just publish the schem as of 
> 2008DEC (before crippling) and start our discussion from there, instead of 
> thinking about doing the whole job (and same mistakes) once again.

Yes, I think it would be great if Openmoko would do this.

- Werner

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