Max,

you find my comments written inline.

Best wishes
Dieter Doepfer

> Hi all,
> I have an amazing problem with my A100 system : it seems to be very
> capricious and it sometimes (about 1/2 probability) blows the fuse on
> power up. The case is a brand new portable suitcase (version 2). I
> tried different types of fuses (200 315 slow or fast, 500 fast), the
> 315 and 200 sometimes work, sometimes blow, the 500mA i tried blew on
> the first attempt but it was not a slow fuse so i guess it's normal.

In any case a time lag/slow blow fuse is required as it has to "survive" the
transient pulse during power on. A fast or medium fuse will blow with a very
high probability. The transient pulse is caused by the type of transformer
(ring core/toroid, higher transient current than for standard transformers)
and as all capacitors of the system have to be charged (e.g. each module
contains capacitors across the supply voltages). A 315mA fuse (time lag !)
should be sufficient from the theory (e.g. the specs from the transformer
manufacturer) for 230V.

> I checked the electric circuit of my home and it's round 238-240 V.

Maybe the slightly higher voltage cause the problem though the difference is
not too much. You could try a fuse that has a bit more mA (e.g. 400 or 500
mA). With this value you are still on the safe side as the fuse will blow in
case of a short circuit or defective primary circuit of the transformer (as
this is the job of the fuse).

> The thing that really amazes me (i don't know if that's the right
> word...) is that the system sometimes work, and sometimes the fuse
> blows. I removed all modules and re-installed them all, nothing seems
> to be wrong inside the case ...

This may be caused by the exact moment when the power switch is turned "on".
If the AC voltage at it's maximum the transient pulse is different compared
to the condition that appears if the switch is operated while the AC voltage
is close to zero. But normally the difference is absorbed by the time lag of
the fuse.

> Is there a simple solution to this problem (special fuse, higher
> current value) What is this fuse protecting What happens if you
> replace this fuse by a conductor Are there some things not to do
> that i should know about modules patching on power up

I'd recommend to use a (time lag) fuse with 400 or 500mA. As mentioned above
you are still on the safe side with this value.

> Thanks for your help and sorry for bad english,
> Max.