2014 imac is killing power supplies

fiveaces

macrumors newbie
Original poster
Oct 30, 2018
6
0
I have a late 2014 27inch imac that seems to be killing power supplies.

model numbers a149, mf886LL/A, EMC2806

I started having random shutdowns. The only way to turn it back on was to reset the SMC by pulling the power cord out and discharging the capacitors. I did everything I could think of to rule out a software problem, including a fresh install of OSX multiple times on different hard drives.
I have been monitoring internal temperatures, using 2 different apps, and nothing seems that unusual. Running the fans at a high speed doesn't seem to effect the shut downs either.

I was pretty sure the power supply was causing the random shutdowns, so I ordered a new one. The mac came with the delta ADP-300AF power supply. The one I bought was a Liteon pa-1331-2a. Can anyone confirm that these 2 power supplies are interchangeable? The website I ordered it from said the Liteon would be compatible with my imac.


I installed the new liteon power supply. imac turned on and was working normal for a few hours. Then it crashed and this time it wouldn't turn on at all.

I returned the power supply, beetstech.com has very good customer service! They sent out a new one free of charge. I just installed it today. The imac was working flawlessly for a few hours. I was editing in indesign and final cut, doing processor and graphics heavy work. Then I plugged in a second external hard drive to reconnect some media in final cut. I heard a pop from the area of the power supply and the imac was totally dead again.

It appears that this thing has destroyed two brand new power supplies. But for some reason the original power supply still works a little bit. I can at least turn the imac on with that one but it will crash frequently.

I'm at a total loss here. Is the logic board bad as well?
 

fiveaces

macrumors newbie
Original poster
Oct 30, 2018
6
0
I have a Back-UPS 550VA UPS for my computer. I'm getting very high voltage readings from my outlets in the house. They are nearly 150 volts when it should be 120V. I am getting the same 150V reading from my UPS I thought that thing was supposed to even out power surges like that. Is this true? Do I have a bad UPS?
 

Silvrbill

macrumors member
Dec 20, 2013
52
2
I have a Back-UPS 550VA UPS for my computer. I'm getting very high voltage readings from my outlets in the house. They are nearly 150 volts when it should be 120V. I am getting the same 150V reading from my UPS I thought that thing was supposed to even out power surges like that. Is this true? Do I have a bad UPS?
Sounds like you have a bad neutral connection either in your main panel, outside at the service entrance or on the transformer itself.
A bad neutral connection will cause high voltage on one side of the panel, low voltage on the other.
Your voltage can fluctuate from 0v all the way to 240v+, more than enough to fry some electrical equipment.
It can also flip flop sides whenever the load changes.
 

fiveaces

macrumors newbie
Original poster
Oct 30, 2018
6
0
Actually it appears that the multimeter I got was broken. I tested it in a different building and I was still getting 150V. That's definitely not right. I got another multimeter and now I'm getting normal readings from my outlets. Usually 118-120V.
If the problem is not coming from my outlets, is it possible that something on the motherboard could be frying the power supply?
 

Silvrbill

macrumors member
Dec 20, 2013
52
2
Sorry, that's all I have to suggest other than to have a close look at the electrical outlet/extension cord/power conditioner or UPS you're using.
Assuming the fact you're using the same outlet/extension cord, etc. suggests to me it's something in the external power supply chain.
Too much of a coincidence to be something else in my opinion.
Also, a bad neutral connection can appear at random intervals, it isn't always consistent.
FYI, I'm a high voltage lineman (35 years+) and I've seen this happen many times.
 
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fiveaces

macrumors newbie
Original poster
Oct 30, 2018
6
0
Sorry, that's all I have to suggest other than to have a close look at the electrical outlet/extension cord/power conditioner or UPS you're using.
Assuming the fact you're using the same outlet/extension cord, etc. suggests to me it's something in the external power supply chain.
Too much of a coincidence to be something else in my opinion.
Also, a bad neutral connection can appear at random intervals, it isn't always consistent.
FYI, I'm a high voltage lineman (35 years+) and I've seen this happen many times.
Thanks for your expertise then. Is there a cheap device I could buy that would alert me of unusual fluctuations in my voltage? Something I could just leave plugged in for a few days.
 

Silvrbill

macrumors member
Dec 20, 2013
52
2
Thanks for your expertise then. Is there a cheap device I could buy that would alert me of unusual fluctuations in my voltage? Something I could just leave plugged in for a few days.
You can buy the voltage/amperage recording devices but they aren't cheap.
Best to have a qualified electrician install them anyway.
Do your lights flicker any?
Get dimmer or brighter?
Do you hear a difference in any fan you might be running?
Do you hear it speeding up or slowing down?
TV, VCR or any electronic equipment shut down or restart unexpectedly?
How old is the house?
In the city or country?
Do you share a transformer with neighbors?
If so, are they experiencing any problems?
 

fiveaces

macrumors newbie
Original poster
Oct 30, 2018
6
0
You can buy the voltage/amperage recording devices but they aren't cheap.
Best to have a qualified electrician install them anyway.
Do your lights flicker any?
Get dimmer or brighter?
Do you hear a difference in any fan you might be running?
Do you hear it speeding up or slowing down?
TV, VCR or any electronic equipment shut down or restart unexpectedly?
How old is the house?
In the city or country?
Do you share a transformer with neighbors?
If so, are they experiencing any problems?

I haven't noticed the lights flickering or changing at all. There are no fans running but I haven't noticed anything else unusual with the electrical current.
Not sure if this could be related but our stove did break a couple months ago. The electrical element that heats the inside was shorting out and sending sparks everywhere. Could that effect the rest of the house?

The house isn't that old, maybe 30 years if I had to guess. It's a rental duplex. I'll ask my neighbors if they have seen anything unusual when I get a chance. I'd assume we are on the same transformer since we are in the same building.
We are in a very small city of about 20,000 people. But it's mostly country around here.