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MDD problem + PS cooling prototype

jbarley

jbarley

macrumors 601
Original poster
Jul 1, 2006
4,023
1,896
Vancouver Island
One of my dual 1.42 MDD has this problem, which I believe is not uncommon.
It runs just fine, good enough actually that is is my favourite MDD of the 4 that I own.
The problem is that every time I shut it down I have to remove the power plug for a few minutes before it will restart. I'm aware that I'm resetting the SMC or PMC whatever when I'm doing this and not sure how long this can go on.
I've actually installed an inline power switch in the power cord to save the wear and tear on the power plug, this works just fine but I'd still like to correct the fault that is causing this issue.
Does anyone have any suggestions?

IMG_0178.jpg
 
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jbarley said:
One of my dual 1.42 MDD has this problem, which I believe is not uncommon.
It runs just fine, good enough actually that is is my favourite MDD of the 4 that I own.
The problem is that every time I shut it down I have to remove the power plug for a few minutes before it will restart. I'm aware that I'm resetting the SMC or PMC whatever when I'm doing this and not sure how long this can go on.
I've actually installed an inline power switch in the power cord to save the wear and tear on the power plug, this works just fine but I'd still like to correct the fault that is causing this issue.
Does anyone have any suggestions?

View attachment 588384
Click to expand...
The PRAM battery isn't dead, is it?
 
Not sure if this helps but on my MDD 1.42 the seller could only turn it on when he connected his adc display and plugged and unplugged the unit. I changed the power supply and it booted just fine for me.
 
Ih8reno said:
Not sure if this helps but on my MDD 1.42 the seller could only turn it on when he connected his add display and plugged and unplugged the unit. I changed the power supply and it booted just fine for me.
Click to expand...
Yes the power supply seems to be the most common thing I find through research, but it is very odd that the unit runs just fine other then the start up issue.
It is not a big deal to shut down then switch-off, I'll probably just run it like this until it ever gets worse, then consider trying a new power supply.
 
The guy I got it from said it ran fine also but needed help to power it on. Its an easy swap and doesn't take very much time. Only thing is if you buy it on eBay its not going to be cheap from what I remember. I lucked out and found a donor unit locally.
 
jbarley said:
Yes the power supply seems to be the most common thing I find through research, but it is very odd that the unit runs just fine other then the start up issue.
Click to expand...

That is the beginning stage.

jbarley said:
It is not a big deal to shut down then switch-off, I'll probably just run it like this until it ever gets worse, then consider trying a new power supply.
Click to expand...

That's pretty much what I would do.
 
I actually have another power supply but the 2 fans in it are noisy, anyone have any experience with replacing these fans with quieter ones?
Specific names-models would be welcome.
 
jbarley said:
I actually have another power supply but the 2 fans in it are noisy, anyone have any experience with replacing these fans with quieter ones?
Specific names-models would be welcome.
Click to expand...
I'd like to know the same thing, for my sanity and for wiki-purpose.
 
Are they Delta AFB0612EH fans? These are the original ones with irritating high pitch noise.
I had replaced them with Neng TYI "two ball bearing" fans (look like this one: http://www.pcstats.com/articleview.cfm?articleid=1049&page=2) for quite a while. There were no specs printed on the fan labels.
I compared the temperatures of PSU's vented air before and after the mod and found they're OK.

Then Apple issued the "downgrade" PSU from 400w to 360w that came with Nidec M34418-16 (25 CFM) fans.
I found the Nidec silent enough to not bothering to do a mod.

PS: I had to alternate the wires (black to red and red to black) for my replacement fans to work, unless they wouldn't spin. Still wonder if that was an Apple's "thing".
 
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Well I've started my journey towards a quieter MDD, I'm in the process of monitoring the PS output air temps, commandeered the wife's remote oven thermometer for the job. Once I have some basic data for comparison I'm thinking of trying something radically different.
Picture a duct from the power supply, a nice smooth 90 degree bend, ending in a large flange to accept a 120mm fan.
Have had really good luck using these 3-speed fans, I'm using a 120mm as the main fan in a dual 1.25 MDD and I've used the 80mm models in my Cubes. I like the 3-speed switch idea, on my Cubes they run at the slowest setting, no sound at all.

Screenshot 2015-10-01 at 2.04. PM.png
 
jbarley said:
Well I've started my journey towards a quieter MDD, I'm in the process of monitoring the PS output air temps, commandeered the wife's remote oven thermometer for the job. Once I have some basic data for comparison I'm thinking of trying something radically different.
Picture a duct from the power supply, a nice smooth 90 degree bend, ending in a large flange to accept a 120mm fan.
Have had really good luck using these 3-speed fans, I'm using a 120mm as the main fan in a dual 1.25 MDD and I've used the 80mm models in my Cubes. I like the 3-speed switch idea, on my Cubes they run at the slowest setting, no sound at all.

View attachment 588710
Click to expand...
What will the ducting be made out of? Take pics when you get cracking!
 
Well here is my "prototype", partly assembled and with the fan ready for a trial.
I've been monitoring the PS exhaust air temps all day and never seen it over 45C, so I have some idea as to what to expect.
I've fired the fan up as a test and it is quiet and pushes a lot of air, tomorrow should tell the story.
I'm starting to think this just might work. :)
Edit: it won't take to much to mount it, basically it'll be sitting on top of the ODD cage.
The little black square is the 3-speed switch.

2015-10-01 20.09.57.jpg 2015-10-01 21.48.44.jpg 2015-10-01 23.07.56.jpg
 
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It would appear that my PS cooling mod is a success, a big success in fact.
This morning I pulled the PS from the dual 1.42 MDD, opened it up and removed the fans.
While it was open I cleaned it best I could then put the cover back on and re-installed it.
I mounted the fan and duct to the top of the ODD cage with a couple of Velcro buttons just to keep it it position.
It's been up and running now for about 5 hours and the exhaust air temperature has not gone above 38C, whereas yesterday it got up to 45C. This is with the fan running at mid-speed 7VDC, 1600RPM and only 28DBA, so I could boost the output if necessary.
 
Last edited:
jbarley said:
It would appear that my PS cooling mod is a success, a big success in fact.
This morning I pulled the PS from the dual 1.42 MDD, opened it up and removed the fans.
While it was open I cleaned it best I could then put the cover back on and re-installed it.
I mounted the fan and duct to the top of the OOD cage with a couple of Velcro buttons just to keep it it position.
It's been up and running now for about 5 hours and the exhaust air temperature has not gone above 38C, whereas yesterday it got up to 45C. This is with the fan running at mid-speed 7VDC, 1600RPM and only 28DBA, so I could boost the output if necessary.
Click to expand...
Sweet! Now I really want to do this!
 
Somewhere during this mod I created a small problem.
The power switch light comes on when I press to start, then goes out and stays out while the system runs quite normally. It does not come on and cycle when the system sleeps, other then the above all works well, little things like this really pic me.
 
jbarley said:
Somewhere during this mod I created a small problem.
The power switch light comes on when I press to start, then goes out and stays out while the system runs quite normally. It does not come on and cycle when the system sleeps, other then the above all works well, little things like this really pic me.
Click to expand...
Mine does this too. Idk how or why..
 
My PS cooling mod is still running just fine, maybe someday I'll get around to making the duct from sheet aluminum but for now the cardboard prototype works well.
The noise reduction over those 2 60mm turbo-fans is a real bonus also.
 
Nice mod, thanks for sharing. The PS issue sounds like an "enable" line is not getting recognized. Dried caps perhaps in the low voltage section.
 
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