Upgrading a G4 Cube

[omidimo]

Be aware though that if your VRM did blow it is likely that it took your logicboard with it on its way out.

Have had this happen twice recently! Dying VRMs are harbingers of doom.

 

[EvilCapitalist]

I actually just got my upspec VRM from Artmix earlier this week...and then discovered there's really no way for me to cram that dual CPU upgrade in there.  Even if I cut out the center of the black heatsink in the middle of the Cube (maintaining the edges for the handle mechanism) I still wouldn't be able to get the card to fit.

 

[MikeatOSX]

They still are selling them:

As far as I know, Artmix is a one man company. I bought several items from him. 

 

[rickrob]

Is there anything that can be done to protect the original VRM's-- Mine is still working but I'm wondering if I should buy one of the Artmix VRM's for my Cube.

 

[Byrd]

Is there anything that can be done to protect the original VRM's-- Mine is still working but I'm wondering if I should buy one of the Artmix VRM's for my Cube.

Additional small heatsinks on the voltage regulators can help, and I also recall on Cubeowner people used to add more vregs, if that was possible.  The usual adding a good 80mm fan (keeping the innards clean from dust) and keeping the video card actively cooled also helps things.

Also, does the Artmix VRM work with all CPU upgrades?  The Powerlogix VRM did not, and I ended up selling mine as it was patchy, to say the least.

JB

 

[Andropov]

Also, does the Artmix VRM work with all CPU upgrades?  The Powerlogix VRM did not, and I ended up selling mine as it was patchy, to say the least.

Some Cube CPU upgrades require the VRM bypass wire even with a custom VRM. Upgraded VRMs were useful for powering better graphic cards and could power some CPU upgrades, not all, but a VRM bypass is always preferred and in some cases necessary.

Is there anything that can be done to protect the original VRM's-- Mine is still working but I'm wondering if I should buy one of the Artmix VRM's for my Cube.

From the old Cubeowner knowledge base:

[SIZE=10pt]Adding extra transistors to the Apple VRM[/SIZE]

[SIZE=10pt]For the Apple VRM, the 3.3 and 5V voltages each involve a bank of power MOSFET transistors; using a pair to pull down and a singlet to pull up. It is the singlet (Q9 or Q7) that usually fail, and since there is an empty space to add a sibling, the idea is to solder in extra Si4840DY units (~$1.50 each). This has been done (requires a steady hand and good soldering skills), and the resulting unit tested and found to be functional in a cube.[/SIZE]

[SIZE=10pt]However, there remains the question as to why Apple did not double up on the pull up transistor, and a line of reasoning that the resulting reduction in switching speed may counter any benefits.[/SIZE]

[SIZE=10pt]All this needs to be considered with the fact that a failed VRM often destroys other parts, which is both reason for toughening it, and reason for not risking the modification.[/SIZE]

[SIZE=10pt]The modified unit is best tested outside the cube, where the enable pin needs to be grounded to turn it on. A superior alternative is simply to purchase the proven stronger GigaDesigns VRM (~$100)[/SIZE]

[SIZE=10pt]This is a 'do at your own risk procedure', as there is the possibility of not only destroying a good VRM, but also of destroying the other parts it is connected to.[/SIZE]

There are empty pads in the Cube's VRM to add an extra MOSFET and it shouldn't be difficult to solder if you have any experience soldering SMD components. The benefits of doing so were still debated when I last checked cubeowner but IIRC the theory that the lack of the second pull up transistor were related to production shortages and not a last minute design change was gaining traction. 

I can attach pictures of the empty PCB pads if you're interested.

 

[rickrob]

Some Cube CPU upgrades require the VRM bypass wire even with a custom VRM. Upgraded VRMs were useful for powering better graphic cards and could power some CPU upgrades, not all, but a VRM bypass is always preferred and in some cases necessary.

From the old Cubeowner knowledge base:

There are empty pads in the Cube's VRM to add an extra MOSFET and it shouldn't be difficult to solder if you have any experience soldering SMD components. The benefits of doing so were still debated when I last checked cubeowner but IIRC the theory that the lack of the second pull up transistor were related to production shortages and not a last minute design change was gaining traction. 

I can attach pictures of the empty PCB pads if you're interested.

I would be interested in seeing the pictures--  Thanks.

I 'm also thinking of making this heatsink for the VRM from some aluminum stock.

http://applefan.tistory.com/10

 

[Andropov]

I would be interested in seeing the pictures--  Thanks.

I 'm also thinking of making this heatsink for the VRM from some aluminum stock.

http://applefan.tistory.com/10

Here is it:

The empty pads where you could add the extra pull up transistors (Si4840DY) are Q3 (top of the image) and Q5 (bottom of the image). Here's the image with the new MOSFET installed from the old cubeowner knowledge base:

 

[rickrob]

@Andropov -- Thanks very much for the pictures. I think I will try to add a pair of Si4840DY to my VRM.

 

[Trash80toHP_Mini]

From the old Cubeowner knowledge base:

There are empty pads in the Cube's VRM to add an extra MOSFET and it shouldn't be difficult to solder if you have any experience soldering SMD components. The benefits of doing so were still debated when I last checked cubeowner but IIRC the theory that the lack of the second pull up transistor were related to production shortages and not a last minute design change was gaining traction.

Interesting stuff. Not a Cube guy, but upgrades in general  .  .  .

1) I wonder if it might have been a lower value MOSFET that was in short supply which made a more expensive, higher capacity replacement more economical?

2) The converse might also be a true, lower prices for a higher capacity single part might have become more economical than dualies in parallel?

3) A lot can change in the periods between design, testing and production. Could a mid-value MOSFET been deemed most appropriate?

4) Pad redundancy could well have been done intentionally for fine tuning/tweaking for the optimal value by testing?

Has an electrical engineer or archival price list aficionado chimed in on the missing MOSFET mystery over there? Just leaving a component out due to a parts shortage for a critical component in a marginal design would be sliced off by Occam's Razor in a heartbeat.

.  .  .  .  can't help myself. Healthy skepticism in observation/analysis/problem solving was drummed into me by the Jesuits at an impressionable age.

 

[CC_333]

.  .  .  .  can't help myself. Healthy skepticism in observation/analysis/problem solving was drummed into me by the Jesuits at an impressionable age.

Good for you! It's always good practice to not simply take something at face value without thinking about what might be underneath the surface (often times, it doesn't take much to find out if you know how/where to look). It must've been... interesting... getting those skills "drummed into" you, though.

What are "Jesuits"?

c

 

[Trash80toHP_Mini]

They're fabulous educators.

 

[beachycove]

Jesuits: A Counter-Reformation Roman Catholic “Society,” the Society of Jesus (effectively a religious Order), but organized on a military metaphor, complete with a General (the founder was Ignatius Loyola, who had been a soldier). Most males would be priests. Some unusual religious practices, like use of imagination in prayer. Long famous as educators (Descartes went to a Jesuit school) and as progressives (e.g., they embraced Galileo’s science, and in fact took it to Japan and China in the 17th century), Jesuits are known for intellectual rigour and missionary labours. The film “The Mission” is pretty clearly based on a Jesuit narrative.

The Jesuits were disbanded in the 18th century on papal authority over their refusal to impose a Latin set of norms on their Chinese mission (the Jesuits had become Mandarins and the Chinese Emperor at the time wrote hymns to Christ and required the civil service to attend church several times a year), and were only revived again in modern times. 

The current Pope was or I suppose still is a Jesuit.

 

[CC_333]

Interesting!

c

 

[Trash80toHP_Mini]

Never really disbanded, survived in Russia and Poland unscathed, IIRC. Jesuit education has been "a thing" for over 400 years. We're waaaay OT here. Suffice it to say that they imposed a bit of order (just a bit) upon my scattershot way of seeing things, symbolic logic helped a lot, but still crazy after all these years.

Really curious about that missing MOSFET mystery, so I tried to lay it out in words.

 

[iKst]

Hi guys, 

sorry for posting in this long forgoten thread. I was just working on my G4 cube and I randomly found this forum. Great info, I managed to troubleshoot my Cube with broken optical drive and some other issues because of the info here. 

That reminded me I have Sonnet 1.8Ghz CPU and upgraded VRM in the closet that I won't be using, so I decided to put the lot on eBay.

https://www.ebay.com/itm/114007959706

I set the price according to the info from this thread, but I may be off, so I am accepting offers, if anyone is interested.