8100 PSU Fan Not Running

[Phipli]

Morning folks.

I bought a spare 8100 style PSU because I'm short of them - I have three dead ones.

The new one is a late 225W version from an 8100/100 and was sold as working. It has a fault I haven't seen before - the fan doesn't run, but it outputs power. I've confirmed that the fan spins when I power it from 5V externally, so the issue seems to be in the part of the PSU that supplies the fan.

The fan board looks... Well done - see attached photos. There also looks to be some cap juice. It would be nice if that was all the issue was, but I suspect that was a cause of another failure.

I guess my questions are...

1. I'm not being dumb am I? The 225W PSUs aren't temperature dependent fan controlled are they? I can't imagine they would be given Apple went to the effort of using a peltier cooler.
2. Has anyone seen this issue before?
3. Has anyone fixed this issue before?

Good news is the logic board seems to work. Bad news is I now have 4 bad PSUs of this type. Sigh. I hate PSU repairs. They're too spicy.

 

[LaPorta]

Holy crud, that is one mucked up board. Have not seen that on any of the three 8100 PSUs I've looked at so far. No, the 8100 PSU fans are not temp-controlled. So what you meant is that the fan jack on the board outputs whatever voltage it is supposed to, but the fan won't run...but the fan does run when powered externally?

 

[Phipli]

So what you meant is that the fan jack on the board outputs whatever voltage it is supposed to, but the fan won't run...but the fan does run when powered externally?

Haven't tested the voltage on the fan header - I try to avoid powering disassembled PSUs. But I suspect it isn't providing the voltage if the fan doesn't turn, but the fan does when I power it directly from a battery.

I'll start troubleshooting it when I have a bit of time

 

[imactheknife]

Hi there Phipli, do you have a caps list? Have two of these to recap

 

[Phipli]

No I don't have a cap list. You can usually pick your own though, the originals usually have the voltage, capacitance and temperature written on them, plus the series sometimes. Then the most important thing is to make sure that the output capacitors are low ESR.

If you're uncomfortable picking capacitors (I'm never not because there is limited info available) it is a good thing to get practice at as most PSUs don't come with cap lists, I find it strange that people keep asking. I personally wouldn't trust someone else's cap list and always go and check myself anyway - what if yours is a different model or revision? Or if someone made an error in their list?

 

[LaPorta]

I have a list, but I have not gone through and modified my list for low ESR and other specifics....resulting in not-well working PSUs.

 

[3lectr1cPPC]

I've been scared of doing PSU cap lists for my site for these reasons. It seems like there were always multiple revisions (and vendors) for each model, and the low esr and frequency stuff that's easy to get wrong.

 

[LaPorta]

I have one that still works with no issues, and two I had issues with that are as a result of not-great recaps. My plan in the future is to nail down the specs of each and every cap exactly from the working one....and then get as close to original parts to fix the other two. If it works...I'll let you know.

 

[Phipli]

I have one that still works with no issues, and two I had issues with that are as a result of not-great recaps. My plan in the future is to nail down the specs of each and every cap exactly from the working one....and then get as close to original parts to fix the other two. If it works...I'll let you know.

Start by replacing the output caps with low ESR parts. The output caps are usually near the output cable, and often a cluster of 1000 to 2200uF caps (ballpark) plus some smaller ones. If you buy new, you can check the ESR on sites like Mouser while selecting based on other parameters.

Guess you know all this, but just in case you don't know physically which caps to target with low ESR parts.

 

[LaPorta]

Hey, I take all the help I can get. I have had a lot of success in the past using Mouser's very capable sorting algorithms, so that is indeed where I will start. I'll do a thread on it when I can, but I am assuming it may be months to be honest.

 

[imactheknife]

Ok, got all of them except the daughter card. Do you remember that one?

 

[LaPorta]

Which do you have? Mine is the AV model, so my card is the AV card. the AV card is just 13 47µf, 16V surface mounts.

 

[imactheknife]

Which do you have? Mine is the AV model, so my card is the AV card. the AV card is just 13 47µf, 16V surface mounts.

Looking at the little daughter card in the psu

 

[LaPorta]

Oh the thing that is really wedged in there....one sec.

 

[LaPorta]

At least on mine:

1 µf, 50V Radial. Diameter: 5.5mm, height 11.5mm
1 µf, 450V Radial. Diameter 10mm, height 13mm

At that point, I was not as careful with low ESR, etc, so I do not have the series marked down, unfortunately.

 

[imactheknife]

At least on mine:

1 µf, 50V Radial. Diameter: 5.5mm, height 11.5mm
1 µf, 450V Radial. Diameter 10mm, height 13mm

At that point, I was not as careful with low ESR, etc, so I do not have the series marked down, unfortunately.

Ok, perfect thanks! I thought it was 1uf 450v but didnt know for sure!