MDD Dual G4 ATX Power Supply swap

[MOS8_030]

Here's a project I did a while back. ATX power supply in a MDD Dual 1.25 G4. This is the FW800 model that won't boot OS9.

I bought this system new back in '03 with the intention of overclocking it to 1.42 but I never got around to it. (I OC'ed a couple 1.25's at work with no problem.)

Anyway, after the power supply failed again for the second time I was almost ready to just let it go.

At one time I had two CD burners and four HD's in it! A truly expandable Mac. (No wonder the PS failed...)

But I got to researching replacements and decided to try to an ATX PS.

Anyway, after investing in a molex pin exactor tool I rearranged the wires to the 24 pin connector, thinking there's no way this will work, but by golly it did!

I had to get a 24-pin extension cable to route around the back of the CD drive so the wires would clear the full-length video card. (Apple nVidia Geforce 4 Ti4600)

I tried mounting with foam tape but that didn't work so I drilled some holes in the top of the case and used screws to suspend the PS.

Anyway, the G4 is humming away again, and despite some reports to the contrary, it seems to sleep and wake with no problem.

Even though I don't use it for much any more except for managing my music collection it's nice to have it back. (old iTunes so much better!)

Here's a couple of crappy work-in-process photos. I didn't get any pictures of the finished install.

 

[maceffects]

On the MDD this is the best investment, I bought 5 new old stock power supplies as spares for my new old stock 1.25ghz FW400 machine, and already used one... 

 

[Trash80toHP_Mini]

Molex extractor? Sounds a lot better than the wire splicing method! Love it, thanks so much for that tip. Looks like tool prices are a low multiple of a package of shrink wrap! Have you got the spec. or linkage to the tool you bought?

What's the rating of the original PSU and how does it compare to the new one? How are your processor temps trending? That form factor PSU and its positioning looks like it makes for a pretty radical departure from design spec airflow.*** Running iTunes is one thing, have you tried running a benchmark app to see how CPU temp fares under stress?

< TLDR mode >

You guys have me thinking about PSU failures, ATX form factors and prospects for retrofitting Apple's PSU cans again. My OS9 special edition MDD remains in mothballs awaiting setup. The QS'02 Dual 1GHz is fine for anything I do with it and the MDD is fun to just mess around with configurations at times. The second processor in the QS doesn't do me any good and a 25% clock bump will be nice whenever it needs to go into service.

It's been a great that the backup machine has been a nice upgrade the last couple of times. It's too bad this MDD is the end of the line for that strategy in OS9. :-/

*** No criticism intended, just wondering if I should look at options for ductwork pattern making. Haven't done that since designing a dust collection cyclone many years ago.  That was fun. Done right it's far more efficient than anything available off the shelf at consumer pricing levels.

The PSU fan is positioned on the backside which is great. Have you noticed a drop in the jet engine noise levels? That aspect of your arrangement looks very promising. Making a smooth, turbulence reducing round to rectangular cross section conversion is what it's all about. At first glance, gradual limitations expansion card profiles a/o "L" shaped PCB stepdown form factors would be required from top to bottom slots. But that might be an acceptable design tradeoff for decibel eradication.

< TLDR mode >

Great topic and very interesting hack!

 

[Trash80toHP_Mini]

Overran editing time limit yet again. :-/

.  .  .  also wondering about noise damping materials choices and chopping a rounded rectangle at @$$ end of this iteration of the PortlyMac case would be a big improvement? That grillwork Apple put inside the plastics is pretty, but I wouldn't be worried about junk falling into ductwork. Not good to have crap land in a PSU, that prospect reminds me of a Star Wars scene! 

Keeping cross sectional area of the transition constant reduces power requirements for cyclone collectors which translates into increased efficiency of the ATX PSU cooling setup in your configuration along with restoring Apple's airflow.

 

[Trash80toHP_Mini]

Just noticed you've removed the HDD cage underneath the optical bay. Have you left it out? Switching to SSDs in the vertical bracket only would increase airflow to the heatsink dramatically. I'm wondering how much that helps in keeping CPU temps down which goes hand in hand with heatsink fan RPM reductions?

 

[MOS8_030]

These posts were my inspiration.

http://atxg4.com/mdd.html

http://www.xlr8yourmac.com/tips/MDD_ps_mods/MDD_PS_Mods.html

http://efeion.blogspot.com/2007/12/power-supply-fun-part-2.html

I used a 600w PS. Since this was an experiment of sorts I didn't spend a lot time doing any research on other possibly smaller form ATX PS's.

For whatever reason, no matter how I used it, this system has never had problem with temperature or the fans.

This was the last iteration of the G4's and has a substantial copper heat sink. The earlier models had aluminum heat sinks.

Whether or not this new power supply will change the equation remains to be seen but I'm doing not much with it so I don't expect any problems.

 

[Trash80toHP_Mini]

  .  .  .  I'm doing not much with it so I don't expect any problems.

That's why I suggested beating the snot out of it with some benchmarking runs just to see what happens! []

THX much for the linkage, I'll be looking at those sometime soon.

 

[trag]

On my list of projects I'll never get to is to try disassembling a few ATX power supplies and then try to fit the circuit boards into the MDD power supply box....

Probably easier just to refurb the components of the MDD supply.

 

[Unknown_K]

I have 3 dead MDD PS supplies currently freezing on a shelf in my garage until I get bored enough to try looking into fixing them. Refurbing will eventually be more cost effective then replacing them with used working units (if it isn't already). Problem is I don't think they are an easy fix and taking them apart is a pain.

 

[MOS8_030]

I researched (i.e. googled a lot) about repairing the original PS's. i could not find any definitive information about a common failure.

I opened up the first one that died (380w model I think) and didn't find anything obviously wrong. My second PS was the later 400w model.

Lacking any starting point for repair and being too lazy to troubleshoot it myself I opted to go the ATX path which I am so far happy with.

If I find heat becoming an issue I'll just stick another pancake fan in it.

 

[Juror22]

I have 3 dead MDD PS supplies currently freezing on a shelf in my garage until I get bored enough to try looking into fixing them. Refurbing will eventually be more cost effective then replacing them with used working units (if it isn't already). Problem is I don't think they are an easy fix and taking them apart is a pain.

I also have 3 dead ones squirrelled away to either repair someday, or to harvest for parts.  I don't need a replacement yet, but I am watching this thread with great interest.

 

[CC_333]

Last time I tried my MDD (Dual 1.42 FW400), it worked (*knock on wood-like substance*)

It's spent the last year in my closet, though, so it may not work now. I should test it and find out.

Anyway, does the ATX mod disable the ADC port? I don't know about the MDD, but on older models so equipped, one either needs a special power supply to provide the needed voltage (24v, I think), or wire in an appropriately rated wall wart. Also, I think Firewire could be a problem, as it also needs a higher-than-average voltage on some of these.

Aside rom that, though, it's much better to have a power supply that a) will not fail like the original, and b ) replacements are easier to find (provided you use the extender cable to carry out the rewiring, it should be plug-and-play).

c

 

[MOS8_030]

Last time I tried my MDD (Dual 1.42 FW400), it worked (*knock on wood-like substance*)

It's spent the last year in my closet, though, so it may not work now. I should test it and find out.

Anyway, does the ATX mod disable the ADC port?

Aside from that, though, it's much better to have a power supply that a) will not fail like the original, and b ) replacements are easier to find (provided you use the extender cable to carry out the rewiring, it should be plug-and-play).

c

Yes it does, but that doesn't bother me. I never used it. As far as FW, I have a FW external HD that seems to be working fine.

 

[Unknown_K]

I have one ADC monitor that looks nice connected to MDD and QS machines so 24V on the PS is good to have.

 

[waynestewart]

You could pick up one of the power supplies for adc monitors. Less load on the computers power supply and then you can use it with quite a few other macs

 

[trag]

There are at least a couple of discussions and at least one parts list for refurbishing the MDD power supply over at https://www.badcaps.net/forum/

I think I posted links on this forum at one time, several years ago.   NOt too hard to search up.

There are cheap (less than $10) buck voltage converters that will let you upconvert 5V  to 24V.     Put one of those on the 5V Standby line of an ATX power supply to provide the 24V standby power the monitor needs.    Put another, high capacity one, on the regular 5V bus of the ATX power supply to provide beefy amperage after the power supply starts up.   Link the output of the two using diodes/rectifiers, so that all the electrons remember which direction they're going.   I think we discussed this at one point a few years back too.

 

[Unknown_K]

Well went to fire up the MDD in my room and it was dead. Wasn't in the mood to figure out why, so I brought up a G5 2ghz DC to replace it.