At 3:12 PM +0100 10/31/99, Holger Marseille wrote:
>Hello Tim,
>
>can you tell me on which board the PMU is located.
>Since my 2400 has the same symptoms and I could have access to another
>2400 for exchanging parts temporarily, I would like to exchange this
>specific board, just to see, if the rest of my machine is working
>properly.
I think the PMU is located on the main logic board (it's the largest
board in the machine). The only other board it could be on is the
I/O / power board which has all the rear panel port connectors.
If you have a solid green sleep light, the PMU is probably alive, but
it may have corrupted RAM contents or some such thing. The challenge
is to reset it, and that can be quite difficult.
>By the way, I tried all this resetting business in all possible
>combinations, but to no success...
Did you try it a lot? It took me more than 20 tries at resetting the
PMU to get my 2400 alive once. (Where each try consisted of holding
the reset button in continuously for 20 seconds or more... sigh.)
>Also in other posts people hinted that even after having their 2400
>repaired the problems came back. Is this an engineering flaw ?
It's hard for me to tell what the problems people are having really
are. I *suspect* a lot of the "dead 2400" problems are solvable by
resetting the PMU. But since the symptoms look like a totally dead
machine to most people, it usually goes to a repair shop.
You could regard the PMU's control program as an engineering flaw. I
know that a lot of people at Apple groan every time they're doing a
new machine and management decides not to completely redo the PMU
because there isn't enough time or budget. The PMU chip and the
program it runs has been more or less the same since the original
PowerBooks; they do slight changes for each new computer to support
new features but most of it stays the same. Some models are known
for having flakier than average PMU code, and generally the 2400/3400
is considered to be about the worst. (The 2400 and 3400's electrical
design and software are virtually identical.)
From all the abuse I've put my personal 2400 through, I have to say
that I'm impressed with its reliability. I have one bad PCMCIA slot,
but I'm very sure I caused that myself while trying to experiment
with activating CardBus support. (I think I damaged the connector on
the motherboard which the card cage plugs in to.) Fortunately I only
need one slot, so I can live with it. Other than that, everything
has survived, even though I must have taken my machine apart and put
it back together at least twenty times by now while trying to play
with various things. I've not even been following good static
discharge precautions.
Tim Seufert
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