I was able to obtain
motherboard photography of a PowerBook G4 with
Gigabit Ethernet showing the countermeasures that
were taken after the repair of a Dead FireWire
When we examine Picture 253
which is a close up of the modified FireWire Port,
an ESD circuit seems to have been added.
Ratoc system Corporation, points this out, but
it seems to be as Picture 250
shows, a 3.3V Step-down DC-DC converter and an ESD
chip. This ESD chip are standard on a PowerBook G4
Is this a design flaw of Apple with all the
older model machines that do not have ESD
protection circuitry. The PowerBook G4 DVI now has
ESD protection circuitry.
I received the following information from Mr.
Please refer to "Release
of small-volume ESD protection element for
high-speed interface". As for us, the ESD chip
was not available until recently.
Performance of the diode in the ESD chip that is
used for the high-speed serial interface of the
FireWire system is excellent. For example,
according to ESD
Protection IEEE 1394 Data Lines(PDF),
aberration of the wave type is minimized if
capacitance between the terminals is kept to about
3pF. A small revision in the content specifications
of IEEE 1394b is expected.
And the Ratoc company also points out, and this
is a special point, that there is a design flaw
with the power supply circuit and bus power of
FireWire PHY. They are not separate, however, they
Next please have a look at the fifth page of
& IEEE 1394 Circuit Protection
Solutions(PDF) which explains the mounting of a
self repairing type fuse.
In the standard circuit, the regulator circuit
(V Reg) of FireWire PHY and the bus power are not
When we examine the
failures, it seems they are easily damaged when
external bus power devices are connected or
It may not be a design flaw, but the absence of
ESD protection elements and the deficiency of the
power supply circuit are largely to blame for the
And there are many cases of machines breaking
down repeatedly. I think that the connection of
external FireWire devices is the cause.
If we can keep the
Firewire circuitry separate from the bus power, we
may lower the rate of trouble or failure. Care in
particular is necessary for pre PowerBook G4
Gigabit Ethernet models which are not equipped with
the ESD protection circuit. At this point it is
still not totally known if this is a design flaw,
but this cannot be ruled out completely. The cost
of the repair is expensive, especially if the
computer is outside warranty.
Special thanks, Mr. D.