G4 Cube FireWire issue

[rcrook9190]

Hi folk,

Been steadily working through the issues with my cube. Two things now haunt the beast

1. The DVD drive eject is not powerful enough to eject the disk. It tries but the disk gets hung up on the foam insert of the case.
2. Neither FireWire port seem to work. With the DVD drive being a dick I tried targeted disk mode and found it doesn't work. Nor does the Cube recognize anything I plug into the ports. Its not reporting errors its just not seeing anything,

Any hints on how to tackle either of these issues would be greatly appreciated.

Regards

Randall.

 

[François]

1. The DVD drive eject is not powerful enough to eject the disk. It tries but the disk gets hung up on the foam insert of the case.

This is a common issue with Apple slot-loading drives of that era. The drives in G3 iMacs have the same problem. See this thread on this very forum!

2. Neither FireWire port seem to work. With the DVD drive being a dick I tried targeted disk mode and found it doesn't work. Nor does the Cube recognize anything I plug into the ports. Its not reporting errors its just not seeing anything,

I have a Cube that was given to me with the same problem. One of the symptoms was that the Cube took a very long time to boot. But looking at the Cube logic board, the damage was obvious:

I replaced the blown capacitor, but that was not enough to repair the logic board. I think the chip to the left of the blown capacitor has overheated and need to be replaced. (at the time, something like 10 years ago, I found it was easier to just buy a replacement logic board on eBay: they were easy to find and relatively cheap)

 

[This Does Not Compute]

Is the bodge on that chip from the factory, or a repair done afterwards? Can't say I've ever seen anything like that before.

 

[rcrook9190]

This is a common issue with Apple slot-loading drives of that era. The drives in G3 iMacs have the same problem. See this thread on this very forum!


I have a Cube that was given to me with the same problem. One of the symptoms was that the Cube took a very long time to boot. But looking at the Cube logic board, the damage was obvious:

View attachment 9984

I replaced the blown capacitor, but that was not enough to repair the logic board. I think the chip to the left of the blown capacitor has overheated and need to be replaced. (at the time, something like 10 years ago, I found it was easier to just buy a replacement logic board on eBay: they were easy to find and relatively cheap)

I will have a close look. Thanks.

 

[François]

Is the bodge on that chip from the factory, or a repair done afterwards? Can't say I've ever seen anything like that before.

It’s from the factory, later Cubes don’t have it, but the chip (a voltage regulator) has a slightly different reference (LM2679 vs LMJ2679).

 

[indibil]

Hello, I have a Cube motherboard with the same symptoms: FireWire failure and excessive heat.

My board doesn't show any visible damage, but instead of the LM2679 with the two diodes, it has an LMJ2679 without the diodes. I can't find either the IC or the datasheet for the "J" version; I can only find the LM2679. Can I replace one with the other? Will I then need to add the diodes? I don't know what values they should be.

Thanks.

 

[François]

The diodes are 1N914B & 1N5231B.

The complete reference for the chip is LM2679 S-ADJ.

I tried to get a good look at the markings on the diodes by moving them around, and managed to break the solder points! It was then easier to read the markings, but a real pain to solder the diodes back in. Much respect to the industry workers who do such rework jobs.

 

[indibil]

Thank you so much for the photos and references!

So, I have one question. I don't have the diodes, only an LMJ2679. If I replace it with the LM2679 without the "J", do I need to add the diodes?

 

[François]

I’m pretty sure the diodes are needed. It’s a factory bodge, it’s manual labor, you don’t do it unless it is absolutely necessary!

 

[indibil]

@François Yes, that's what I thought, but the Cubes that use diodes come with LMs, while mine, without diodes, uses an LMJ. I can't find a datasheet for the J. My motherboard doesn't have diodes. Do I need to add them? Or is it already implemented in my motherboard revision?

Are the LMJ and LM the same component? Or are there differences?

 

[Certificate of Excellence]

I’ve been following this as I’ve always wanted a cube and figure someday maybe I’ll run into one that will jump into my office and refuse to leave

Anyhow, I obviously did not know so I asked the great google ai & it said this on the difference, interchangeability of LMJ2679 & LM2679, & if they both need the bodge:

• Version Difference: The "LMJ" prefix typically indicates a specific, sometimes proprietary or older, production variant of the standard LM2679 IC.
• Application: Both are part of the voltage regulation circuitry, often regulating input voltage down to 3.3V or 5V. [1]
• Functionality: Both offer a 260kHz fixed-frequency internal oscillator, a 120m\(\Omega \) DMOS power switch, and a 5A maximum output current. [1, 2]
• Interchangeability: While often performing the same role on the board, the LMJ variant was associated with earlier board revisions. Later G4 Cube revisions often used standard LM2679 markings and did not always require the same factory modifications. [1]

If repairing, you should ideally match the marking (LMJ2679 or LM2679) to the original part, though they are generally designed to fulfill the same function.

Again, this is AI sifting the internet for likely answers so take this with a grain of salt but I thought it was interesting.

 

[JDW]

I have dealt with two Cubes at the office and one personal Cube at home, all of which had issues with their FireWire Ports. In my case, all were fixed with DeOxit D5 sprayed into the FireWire connectors from the outside. I did that for the USB connections too, because one Cube had an iffy connection on those. Connectors inside the Cube can suffer from oxidation as well, and D5 helps out there too. Obviously, it's not going to fix burned out component issues, but it's a first start in the troubleshooting process, simply due to the fact that connections can and do corrode over time.