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Modern G4 Cube PSU replacement?

danyetman

Member
Nice! If only we could find one closer to the stock PSU it'd be perfect. Would be nice to be able to power ADC displays also. I think I'd probably be most comfortable running it on the 110 just for some headroom.

This is the same series, but 165W instead of just 80W, which is pretty close to the 205W of the original. At $196, it's a bit more than twice the price of the 80W model, but you might find that an acceptable tradeoff for the overhead.
 

Stephen

Well-known member
The new Apple USB-C power bricks for the M1 Max / Pro laptops are 28v @ 140w. This is more than enough to run a G4 cube (which is not using an ADC monitor). Older USB-C adapters may be sufficient in some circumstances but I don't believe they have sufficient wattage / headroom for spikes.

The hard part is getting a USB-C connector adapter that's rated for 28v @ 140w because it appears to be a new addition to the standard. However, once an adapter is available you would basically end up with a very short adapter with USB on one side and the G4 cube plug on the other. Sounds dreamy.
 

gogopuffs

Well-known member
So taking a look at the notes of previous experimenters, I went ahead and bought a Mean Well LRS-350-24 voltage-adjustable power supply and butchered one of my LaCie power supply bricks that had the right power connector. Carefully testing and retesting the pinouts for the G4, of the donor cable, I saw that the wiring was effectively 'swapped' (the original ground and V+ need to be hooked up opposite on the Mean Well). I cranked up the voltage dial and then dialed it a little lower as it was 29.8v or so, and made sure that my cables had strain reliefs on them. Please note that if you choose a similar hardware setup that your wiring colors may differ and should be tested and verified before plugging anything in.

I was a little frustrated with the pictures out on the Internet so I decided to snap some photos of my own in case anyone else wants to do something similar.

overall.jpgclose-up.jpglacie-donor.jpg
 

gogopuffs

Well-known member
Huh, it seems that there's a ready-made replacement G4 power supply that people can just buy without fiddling with making their own cables:

TDK DTM165PW280C. (28v, 165w with right connector) Seems to have the right connector, appropriate voltage and power pinout, and is in stock in various locations. I'm thinking the new asking price is about 2-3x higher than normal because of the medical designation. Might be worth it (plug and play ready, 3 year warranty) for some of you though.

The product family Datasheet is linked and attached for your convenience.
 

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gogopuffs

Well-known member
Word of warning mind you regarding that TDK power supply - please verify pinouts and power requirements of any application or possible replacement before taking advice off of a casual commenter on the Internet!
 

ried

Well-known member
What's the current status of third-party PSU replacements for the G4 Cube? My Cubes have a couple of power supplies that do not appreciate the Sonnet G4 upgrades, GeForce 3 upgrades, and ADC Cinema Displays attached to them. Power inevitably cuts out from the stock PSU.

Are any of those third-party units (TDK, etc.) up to the task? Better yet, can the stock PSU be refurbished to original spec?
 
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Daniël

Well-known member
Are any of those third-party units (TDK, etc.) up to the task? Better yet, can the stock PSU be refurbished to original spec?

The main problem with them is failing caps. You can recap the power supply, but you basically can't do it without some slight damage to the outer shell. You need to enlarge one of the holes furthest to the left or right of the supply (the side that slope off), nearest to one of the covers, so you can put in a tool to pry one of the clips holding the side covers off inside of the unit. I prefer the IEC cover, as you're not dealing with attached cables in your way.

Some guides say you need to do both, but I found that just the IEC side is enough, you can slide the unit out of the plastic housing through that side. Then it's a matter of disassembling the metal inner housing, and removing the soldered-on, plastic covered copper sheets on the bottom of the PCB, after which you can replace the caps and reassemble.

I managed to pull it off, but it is not fun.
 

ried

Well-known member
Sounds like someone who enjoys recapping could turn this into a money-making hobby.
 

tjchris84

Member
I see this is an old thread, but for documentation's sake, you could get a Dr. Bott DVIator and the power supply plugs right in to the Cube and works fine. Unfortunately they aren't readily available to purchase any more.

Amazon listing, no longer available but you can see the connector.

You can see the plug is the same, I used to use this on my G4 Cube before it was stolen from my house. The wattage is lower so it can't also power an ADC display, but it powered my Cube fine using VGA.

Hope this helps someone else that stumbles across this thread. Back in the day, this whole kit was far cheaper than a PSU ($100 or so IIRC)
 

François

Well-known member
What’s stranger is that Apple allowed them to resell Cube PSUs in the first place! I bought a DVIator back in the day, it definitely came with a Cube PSU. Having a spare proved to be very useful.

I watch Cube listings on eBay and spare Cube PSUs seems quite common.
 
I just found this PSU on DigiKey that should work great on a cube if you can make a cable (or are willing to harvest it from a stock PSU). It is rated for 240W and has enough connections to make hooking up the 4 wires easy. The voltage is slightly lower than stock at 27.6v, but I don't anticipate any issues from that. It is also relatively inexpensive all things considered. The extra wattage can really help if you are running a cube with big upgrades. Larger GPUs will pull 30-50W and later model G4 CPUs will pull 20-30W each. If you are lucky enough to have a Radeon 9000 and a dual 744x CPU upgrade in your cube, it could easily pull almost 100W without even considering an ADC display and USB/FireWire devices.

 
I think it would also be cool to take something like this chassis mount PSU and make a 3D printed case for it for more of a stock look. That would be a lot more work, more expensive, and require mucking around with mains voltage... But it would be sexier than a plain black box.
 

herd

Well-known member
My two Cubes came without the power bricks. I've always just run them on 24v, which seems to be a more common voltage for things. This also seems to help the VRM run a little cooler and most firewire drives seem happier too. Even though the firewire spec allows up to 28v, I've repaired several that had converters only rated for 24v. I think that was the last time I bought something from OWC. The ADC screen works fine with 24v too.
 
In general, yes, I do believe that 24v should work just fine. It will allow the VRM to run cooler in most circumstances. There are two downsides though:
  1. The wattage consumed by things running on the higher voltage will not change. This will result in a larger amount of current flowing through the pins that power the VRM, FireWire ports, and ADC monitor. I'm not sure if anything you can put in a cube will push it hard enough to melt something. I do know that the pins leading to the VRM are rated for 9A from the 28v side and I'm not sure what the ADC connections are rated at. The VRM should be perfectly fine from a current perspective with 24v (216 W is more than a stock cube PSU can even supply), but I'm not as knowledgeable about the power delivery to ADC displays.
  2. In general, the closer you get to 50% duty cycle on a buck converter, the more stress it places on the input capacitors. Reducing the input voltage will put more RMS current through the electrolytic input cap and likely lead to it failing sooner. How much sooner is an open question though and it should be relatively easy to replace. I have actually already replaced the caps on mine with polymer caps of a lower ESR and it seems to work fine. Perhaps if 24v does cause capacitor issues, a simple recap of the VRM with lower ESR caps could be a great way to compensate. Again, though, I'm not sure how this will impact ADC monitors as I've never taken one apart to see how the power delivery is configured.
 

herd

Well-known member
I think the most direct cause of VRM failure in the Cube is high temperature, specifically on the FETs for the 3.3v and 5v supplies. Even a completely stock Cube setup will have a relatively hot VRM, but often CPU and/or GPU upgrades exacerbate the situation and thus get the blame. Running on 24v input (vs 28v) does slightly help reduce temperatures, though replacing the FETs helps more. This shows a Cube running outside of its case with a stock GPU only displaying Finder and the desktop, and an upgraded Dual 1.2GHz CPU with both processors fully loaded. The VRM is stock except that the 5v FETs have been replaced. Notice that the 5v section of the VRM is running cooler than the 3.3v section, despite the stock GPU not doing much and the upgraded CPU under full load.

vrm.jpg
 
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