2400c query

[beachycove]

I received a Powerbook 2400c in the post yesterday, with the usual symptoms (DOA). There are some people around here with experience of these machines, and I have two questions:

1. I have taken the top case off and taken a look, with a view to disconnecting the backup battery, but it is very hard to tell where the battery connects with the logic board, as the internals are all packed in so tight. Do I need to take the logic board out and turn it over the see the backup battery connector, or is it one of the two small plugs visible on the top of the logic board (one at the left and one at the right)? I would rather not attempt a complete disassembly just yet as all I want to do is to disconnect the battery, leave it overnight, and then quickly reassemble and see if it will boot.

2. There are two very small wires leading from fuses or capacitors (hard to tell, they are so small) on the logic board, but only soldered down at one end. This was certainly not a hack, as the work was clearly done at factory level, but I wonder if the other end is meant to be soldered down as well (that would seem to be obvious). What are these wires for, and are they indeed normal on a 2400c?

There is very little information on the web about the 2400c, as it is a rare machine, so any help would be much appreciated.

 

[tomlee59]

I've not had the pleasure of opening up a 2400c, but I'd recommend just plugging it in and leaving it to charge for as long as patience allows. If the pram battery isn't shorted, then this might give it enough juice to allow the 'book to power up. If this works, it would save you a bit of trouble...

 

[Franklinstein]

I've had those things opened more times than I care to remember, so I'll take a crack at answering your questions.

1. The PRAM battery is a small pack of NiMH batteries mounted near the front of the main battery compartment, beneath the motherboard. It should barely be visible around the right edge of the board. The battery uses a very long cord that runs around to the front left of the motherboard, and plugs in right next to the RAM slot, beneath that metal shielding bit which must be removed to access it. Two screws are all that hold it in.

2. Those little wires you're talking about were installed at the factory to disable CardBus support. At least, on that board revision; some had different was to disable it. Supposedly there were issues with CardBus, mostly in software, and instead of working out the issues, Apple just had IBM turn it off. Desoldering or snipping those wires restores CardBus, and as long as you're running 8.0 (preferably 8.6 or above), it works just fine. I've never had problems with CardBus USB or networking cards, anyway.

 

[beachycove]

Ah, so mine is Cardbus dis-disabled. That is interesting. Someone has already tinkered.

Following this up, I want in again and noticed when rootling around inside that someone had taped a message "SCSI port bad ?" on the scsi connector.

The machine still will not boot, despite disconnection of the pram battery and various little dances performed.

Is it fuse time, do you suppose?

 

[TheNeil]

It could be the PMU playing up. Mine did this and the procedure for getting it up and running again is somewhat hit-and-miss.

From memory you need to unplug the machine from the mains, remove the main battery and then leave it for some time (the advice I remember is over-night but I seem to think that a couple of hours was enough). Then hold down the reset switch on the back for 30 seconds. Re-connect the power, hold down the reset switch again (for another seconds) and then try powering it up.

On my machine this worked for a while and then gave up the ghost (like you I removed the PRAM battery thinking that it'd help - I'm not certain whether it did or not)

If you do get anywhere with the fuse then I'd definitely be interested to know what you did

 

[beachycove]

It could be the PMU playing up. Mine did this and the procedure for getting it up and running again is somewhat hit-and-miss.
From memory you need to unplug the machine from the mains, remove the main battery and then leave it for some time (the advice I remember is over-night but I seem to think that a couple of hours was enough). Then hold down the reset switch on the back for 30 seconds. Re-connect the power, hold down the reset switch again (for another seconds) and then try powering it up.

On my machine this worked for a while and then gave up the ghost (like you I removed the PRAM battery thinking that it'd help - I'm not certain whether it did or not)

If you do get anywhere with the fuse then I'd definitely be interested to know what you did

Yes, I followed your sorrows in these fora at the time, as I've been on the look-out for a 2400.

I still can't make it boot, but will persist a while longer before abandoning the attempt, given that the reputation of the machine is one of extreme temperamentality. I have wondered elsewhere whether I could try recharging the backup cells in my Duo (2.4v in the Duo vs. 3.6v in the 2400, however - but I don't think I have any machines using 3.6v pram cells, and would not want to try it in something that recharges at higher voltage, like a Wallstreet). Alternatively, I suppose I could jury-rig an ordinary 3.6v Lithium just to see if it would awaken the 2400 - if the main battery does not charge, 'tis said, the machine will not try to charge the backup battery, so no explosion for the purposes of the trial. Hmmm. Any opinion on that one? It would only be in there for a few minutes.

Failing this, I'll likely just disassemble it and bring the boards/ cards to a specialist for component-level (i.e., SMT fuse) testing/ repair. The result would certainly be more reliable than if I tried to do it myself! I can do many things, and some of them I even do rather well, but these things do not include component-level electronics repair.

All in good time.... Having just bought the thing, I'd best save my pennies or flog some spare gear in order to finance the next phase. Otherwise the hobby becomes a little too absurd.

 

[Franklinstein]

Two of mine (I have four) didn't work properly when I bought them.

The first one had a bad fuse on the main board, on the underside, and the processor card didn't like to seat properly. Replacing the fuse and ensuring the assorted cards were installed properly got that one to work.

The second one worked every now and then: some days it booted on command, some weeks it wouldn't boot at all. After some component swapping, I discovered that the power/IO board was bad. No fuses were bad, no components were bad, but it still wouldn't work; any board from a different machine would work, but the old board wouldn't work in any other machine. So, since I couldn't find a schematic or anything for it, I just replaced it. The new board works in the one machine with no problems.

Replacement boards are occasionally seen on eBay, which was where I got mine.

Those machines will usually boot without any batteries installed, they're not like the Mac II or an LC or anything. If you're not even getting the GLOD, you might want to check that everything is seated properly, followed by the little fuses. There are like 14 of them spread between the power board and motherboard.

 

[beachycove]

I have sourced a replacement power board on eBay and will be trying to get the 2400c up and running over the weekend. Thanks for this lead; will post the results.

 

[beachycove]

Thanks to advice offered here, I replaced the power board in the small hours of the morning. It worked; the machine bonged and started up right away after reassembly.

Ahem: not only do I have a working 2400c, but a 2400c with 80MB ram, and - what I can scarcely believe - the battery gauge is showing two and a half hours of charge on the battery, and that is with the drive spinning. The disk (3 GB) is noisy, however, and will be replaced by a CF drive, methinks, as I have done that before on a 2300c and really, really like the result.

As yet, the backup battery is not alive, but the machine has as yet been plugged in only overnight. I gather that even a new backup battery needs a few days on the mains to charge. If it does not revive, a replacement will be a must, as the machine is too fussy to go without those little coin cells.

Happiness is (just now) a functional 2400c.