iMac G5 iSight cooling mod PSU question

[netsrot39]

Hello,
I know that iMac G5s have a bad reputation for running too hot and mine is no exception. I own a 20" iMac G5 iSight from late 2005 and it is an oven. I'd like to change that and for that reason I intend to put more fans into the chassis. After some measuring I came to the conclusion that I can in fact add 6 additional fans that would draw about 6 watts extra from the power supply. I'll power those additional fans by using a SATA Y cable, i.e. splitting the SATA power connection and putting a SATA to 8x 3pin Molex adapter on one end. As of now I have two small fans mounted by using double adhesive tape near the northbridge in my iMac (each draws 0.05A) and discovered that the northbridge is now running about 10-15 degrees celsius cooler. Now I wanna ask you guys if the additional power draw could lead to problems?

What else did I change in the system?

• swapped 3.5" hard drive for a 2.5" SSD
• swapped the optical drive for a caddy with another 2.5" SSD

These two upgrades should spare some watts, right?

Does anyone know how many watts these iMac G5s use when under full load? I can tell that the power supply is rated 185W. I know that additional power draw will eventually create more heat but I anticipate that with 6 additional fans the iMac G5 will run noticably cooler. Nevertheless I wanna ask you guys first because I'm not really an electricians expert. Furthermore I can't do the mod right away anyway since some parts are still on their way from China. Attached please find my planning.

Is there anything else I might not have considered?

Thanks for your help!

 

[tigerintank]

I'd advise caution with stressing your psu even bit more than standard -only because of the well known 'capacitor issues'.

Also since the iMac was designed with those higher temps in mind, maybe you might think about balancing heat reduction with increased stress on the psu.

The SSD will generate less heat than the 3.5 original so that's a plus.

Not sure how 2 x SSDs power draw compares to a 3.5 + Optical that runs occasionally. If you save enough, maybe the fans wouldn't increase the overall load on the psu.

 

[netsrot39]

I'd advise caution with stressing your psu even bit more than standard -only because of the well known 'capacitor issues'.

Also since the iMac was designed with those higher temps in mind, maybe you might think about balancing heat reduction with increased stress on the psu.

The SSD will generate less heat than the 3.5 original so that's a plus.

Not sure how 2 x SSDs power draw compares to a 3.5 + Optical that runs occasionally. If you save enough, maybe the fans wouldn't increase the overall load on the psu.

Thanks for replying. I might cut back to 4 fans in total. The 2 near the northbridge are a must however since the memory controller goes up to 90°C (basically independent from CPU-usage) elsewise which is definitely too hot. A 3x3x1cm fan near the optical drive and a 5x5x1cm one on the SSD should be enough to keep the machine a little bit cooler. So the additional load on the PSU now would "only" be 3 watts. Is it safe to assume that replacing the original 3.5" drive with an SSD would cut the wattage in half, i.e. for example instead of 10W only 5W are used. Unfortunately I haven't been able to find exact numbers on hard drive power consumption. And you're probably right, replacing the optical drive with another SSD will cause some additional power draw. Just to be sure, I'll get a watt-meter and do some "before and after" testing once the parts have arrived. I'll report the results here of course. In the meantime I'd love to learn more about you're experiences, thoughts or suggestions if you have any.

Thanks!

EDIT: One thing that also came to my mind is moving the temperature sensor to a hotter part in the machine like for example to the metal heatsink. Of course this would report wrong temperatures of the hard disk / SSD but it would cause the system to ramp up the fans if my assumption is correct. What I also noticed is that the S.M.A.R.T data of both SSDs report higher temperatures than the temperatue sensores of the iMac (about 10-15°C higher). Even if the temperature sensors would be moved to the "wrong place" in the machine to provoke the fans to kick in, I could still read the temperature by using the S.M.A.R.T data.

 

[1042686]

If you did add some fans and blew some caps in your psu, a replacement psu cap kit for iSight iMac g5 is only $9 bucks on eBay so a pretty cheap & straightfoward fix.

What about running usb power from external wall 110v bypassing the psu altogether?

 

[tigerintank]

I have a 20" 2.0GHz ALS

My experience is that my original PSU died - symptoms were machine would switch off randomly within an hour or 3 or so of startup.

I took a chance and recapped the PSU as my easiest option and it was fine for a month or so iirc then the PSU went completely - no power up.

Next I switched to an ATX PSU and that lasted for a year and a half - warranty replacement and upped the capacity - no problems since.

My guess is the main board caps are suspect and placing some sort of extra stress on the PSU - that a beefier supply is capable of coping with.

I have 2 x HDDs attached but mounted outside the iMac - sata cables through the ventilation slot - dremeled the steel behind the white plastic.

I bought a remote sensor that had been stripped out of a mackbook and soldered a USB end on - I'm now able to use my Apple Remote.

I don't use mine for much these days - audio server / backups of other machines / occasional video but I'm keeping an eye on the MintPPC thread from Jeroen Diederen. I'd like to be able to use the iMac more - it really looks like his (and others) work may make it possible.

 

[netsrot39]

If you did add some fans and blew some caps in your psu, a replacement psu cap kit for iSight iMac g5 is only $9 bucks on eBay so a pretty cheap & straightfoward fix.

What about running usb power from external wall 110v bypassing the psu altogether?

That is good to know. So even in the worst case scenario it could be repaired fairly inexpensively. Other components aren't really at risk of breaking with this modification, right?

I did the math again, like I wrote before I'll only put in 4 additional fans in total (so 3 extra watts)

The original hard disk draws 5V DC 0.92A and 12V 0.90A which should translate to 15.4 watts tops
The original optical drive draws 5V DC 2A which should be 10 watts when used to its full potential

By removing the original hard disk and replacing it with an SSD (3-4 watts) and attaching 4 additional fans (3 watts) I should have at least saved 8 watts. I don't know how many amps the SATA to molex adapter draws but considering it's quite a small circuit board it can't be more than 1 watt.

By removing the original optical drive and replacing it with an additional SSD I should have also saved about 6-7 watts. I don't know unfortunately how many watts an optical drive uses when idle.

I'm taking the maximum wattage as a basis here but I think that is one ought to do when it comes to calculating power supply consumption.

If my math is right, I don't see any problems at all with my fan addons.

I have a 20" 2.0GHz ALS

My experience is that my original PSU died - symptoms were machine would switch off randomly within an hour or 3 or so of startup.

I took a chance and recapped the PSU as my easiest option and it was fine for a month or so iirc then the PSU went completely - no power up.

Next I switched to an ATX PSU and that lasted for a year and a half - warranty replacement and upped the capacity - no problems since.

My guess is the main board caps are suspect and placing some sort of extra stress on the PSU - that a beefier supply is capable of coping with.

I have 2 x HDDs attached but mounted outside the iMac - sata cables through the ventilation slot - dremeled the steel behind the white plastic.

I bought a remote sensor that had been stripped out of a mackbook and soldered a USB end on - I'm now able to use my Apple Remote.

I don't use mine for much these days - audio server / backups of other machines / occasional video but I'm keeping an eye on the MintPPC thread from Jeroen Diederen. I'd like to be able to use the iMac more - it really looks like his (and others) work may make it possible.

Do you know if the PSU problem is also widely present in the iSight line?

I really don't want to install a PC power supply in my iMac, I still want it to be a neat and compact machine that I can easily carry from room A to B.

For now I'm staying with OS X on PowerPC (as long as there are browser updates like TFF). Once that is history (I hope not too soon) I'll install Linux granted my PowerPC machines don't refuse to do their job for some reason by then.

 

[tigerintank]

Iirc HDDs use most power at spin up, less when in use and obv least at idle. Not sure of SSDs.

Not sure re iSight PSU status -might be others on here who can vouch for them.

Understand your pref re MacOS -may stay there myself, depending on how MintPPC goes.