You are here

Odd fuse blowing. iMac 2010

For current or would-be users of Apple Mac computers, with answers to many FAQs.

Odd fuse blowing. iMac 2010

Postby DAGGILARR » Wed May 08, 2019 5:21 am

Hi. I run a 2010 iMac i7 27". About six months ago I had the original 2tb HDD drive removed, and replaced it with a 1tb HDD and put a 1tb SSD in the optical bay. It has all worked fine with no issues. yesterday evening when I returned to the keyboard and hit the space bar, (my normal method of waking it) nothing, the machine would not boot. i changed the fuse in the power lead plug and that was the problem. This morning , the same thing has happened, another fuse has blown! replaced it, boots fine. the first fuse was 10amp, the new ones are 13. I don't have any 10s. Has anyone any ideas what may be causing this?
User avatar
DAGGILARR
Frequent Poster
Posts: 758
Joined: Wed Sep 22, 2010 12:00 am
Location: Exeter, Devon.
iMac 27" i7 2.9gh 2010 12GB ram, Focusrite Pro24DSP.

Re: Odd fuse blowing. iMac 2010

Postby DAGGILARR » Wed May 08, 2019 8:09 am

As a precaution I have used an alternate power lead with a 10 amp fuse, I have plugged that into an extension lead protected by a 5amp fuse and that, in turn, to a different outlet, albeit on the same circuit.
User avatar
DAGGILARR
Frequent Poster
Posts: 758
Joined: Wed Sep 22, 2010 12:00 am
Location: Exeter, Devon.
iMac 27" i7 2.9gh 2010 12GB ram, Focusrite Pro24DSP.

Re: Odd fuse blowing. iMac 2010

Postby BigRedX » Wed May 08, 2019 8:20 am

On a device with a detachable power lead, the fuse in the plug is there to protect the lead itself and not the actual device. The fuse used should be rated for the lead.
User avatar
BigRedX
Frequent Poster
Posts: 672
Joined: Fri Sep 03, 2004 12:00 am
RockinRollin' VampireMan

Re: Odd fuse blowing. iMac 2010

Postby DAGGILARR » Wed May 08, 2019 8:41 am

BigRedX wrote:On a device with a detachable power lead, the fuse in the plug is there to protect the lead itself and not the actual device. The fuse used should be rated for the lead.
Hmm , Interesting. so what protects the device?

What I don't understand is why that fuse has blown twice. when there are three other things plugged into that extension lead, and nothing else has blown.
User avatar
DAGGILARR
Frequent Poster
Posts: 758
Joined: Wed Sep 22, 2010 12:00 am
Location: Exeter, Devon.
iMac 27" i7 2.9gh 2010 12GB ram, Focusrite Pro24DSP.

Re: Odd fuse blowing. iMac 2010

Postby DAGGILARR » Wed May 08, 2019 9:01 am

Another fuse just blew. it was the 10amp not the 5 in the plug board
User avatar
DAGGILARR
Frequent Poster
Posts: 758
Joined: Wed Sep 22, 2010 12:00 am
Location: Exeter, Devon.
iMac 27" i7 2.9gh 2010 12GB ram, Focusrite Pro24DSP.

Re: Odd fuse blowing. iMac 2010

Postby ef37a » Wed May 08, 2019 9:32 am

BigRedX wrote:On a device with a detachable power lead, the fuse in the plug is there to protect the lead itself and not the actual device. The fuse used should be rated for the lead.

Quite. A computer that draws less than 400W max should not take out a 10 amp mains fuse even allowing for inrush current. I would hazard a mains spike coinciding with switch on but I would still expect an internal mains fuse to blow instead or at least as well as.

The mac now seems to be working ok? That just leaves the very rare event of a faulty fuse as the culprit. I would suggest not buying fuses from the corner shop but get branded ones from an electrical retailer, though I have to confess, in a long and undistinguished career in retail electronics servicing I have never come across dodgy fuses! Self igniting 13A plugs yes but not fuses.

Dave.
ef37a
Jedi Poster
Posts: 10377
Joined: Mon May 29, 2006 12:00 am
Location: northampton uk

Re: Odd fuse blowing. iMac 2010

Postby BigRedX » Wed May 08, 2019 9:49 am

DAGGILARR wrote:
BigRedX wrote:On a device with a detachable power lead, the fuse in the plug is there to protect the lead itself and not the actual device. The fuse used should be rated for the lead.
Hmm , Interesting. so what protects the device?

What I don't understand is why that fuse has blown twice. when there are three other things plugged into that extension lead, and nothing else has blown.

There should also be a fuse inside the device itself, normally located by the mains input socket.

I would suspect a dodgy mains lead. Do you have another one you can try?
User avatar
BigRedX
Frequent Poster
Posts: 672
Joined: Fri Sep 03, 2004 12:00 am
RockinRollin' VampireMan

Re: Odd fuse blowing. iMac 2010

Postby ef37a » Wed May 08, 2019 10:01 am

I am just wondering if the iMac has VDR surge limiters PRE internal fuse?

Maybe invest in a UPS? I suspect they are better protected from mains spikes than computer supplies. Not that we get any trouble with our mains supply really. Don't waste your money on "surge protected" diss strips.

Dave.
ef37a
Jedi Poster
Posts: 10377
Joined: Mon May 29, 2006 12:00 am
Location: northampton uk

Re: Odd fuse blowing. iMac 2010

Postby DAGGILARR » Wed May 08, 2019 2:14 pm

So far it has blown , in this order 1 10amp, and 2 13amp, amp another 10 amp. I have used an alternate lead.

It only seems to happen when it is asleep. I return to it and hey presto blown fuse. The last thing I did was put in the 10 amp and plugged the lead into an extension protected by a 5amp. The 10 blew. So whatever It is, is happening on the computer side, not the power outlet side. At this point I have 5amp fuses in and I have switched off all sleep modes. It still runs fine.

I am thinking that I must have a dodgy power supply in the iMac. That it surges when waking to index or time machine or something.
User avatar
DAGGILARR
Frequent Poster
Posts: 758
Joined: Wed Sep 22, 2010 12:00 am
Location: Exeter, Devon.
iMac 27" i7 2.9gh 2010 12GB ram, Focusrite Pro24DSP.

Re: Odd fuse blowing. iMac 2010

Postby Hugh Robjohns » Wed May 08, 2019 2:31 pm

DAGGILARR wrote:I am thinking that I must have a dodgy power supply in the iMac. That it surges when waking to index or time machine or something.

That would be my guess too... When 10 and 13A fuses in mains plugs and plug boards start blowing something is seriously wrong somewhere... It takes both extremely high and sustained currents to blow those fuses normally -- although some will blow purely through old age and/or repeated surge stresses.

H
User avatar
Hugh Robjohns
Moderator
Posts: 23474
Joined: Fri Jul 25, 2003 12:00 am
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: Odd fuse blowing. iMac 2010

Postby DAGGILARR » Thu May 09, 2019 6:03 am

The machine ran fine for several hours with a 5amp fuse, I had a document that had to be finished. I have now shut it down. So it does seem that it only does this when waking itself from sleep. Is there any possibility that an SMC reset would help? I am fearful about any further experimentation as to do so would involve seeing if it did it again, and as has been pointed out, it takes a belt to blow a fuse, which has to be risky for the machine, allthough it does appear to work fine if it is set to never sleep. Can I risk using it in this mode?

If it needs a new power supply I wonder how much this will cost and if it is worth it for such an old, albeit very capable, machine.
User avatar
DAGGILARR
Frequent Poster
Posts: 758
Joined: Wed Sep 22, 2010 12:00 am
Location: Exeter, Devon.
iMac 27" i7 2.9gh 2010 12GB ram, Focusrite Pro24DSP.

Re: Odd fuse blowing. iMac 2010

Postby zenguitar » Thu May 09, 2019 12:06 pm

I think it's time to talk to Apple and see if they are aware of any known causes or solutions. Difficult to identify the real cause online so any advice would be uncertain.

Andy :beamup:
User avatar
zenguitar
Moderator
Posts: 9142
Joined: Thu Dec 05, 2002 1:00 am
Location: Devon
When you see a fork in the road, take it.
Yogi Berra

Re: Odd fuse blowing. iMac 2010

Postby DAGGILARR » Thu May 09, 2019 12:10 pm

zenguitar wrote:I think it's time to talk to Apple and see if they are aware of any known causes or solutions. Difficult to identify the real cause online so any advice would be uncertain.

Andy :beamup:

They couldn’t help, offered to recommend a certified Apple repair centre. I have someone I can take it to, so until I do it’s shut down. I just did a backup this morning.
User avatar
DAGGILARR
Frequent Poster
Posts: 758
Joined: Wed Sep 22, 2010 12:00 am
Location: Exeter, Devon.
iMac 27" i7 2.9gh 2010 12GB ram, Focusrite Pro24DSP.

Re: Odd fuse blowing. iMac 2010

Postby zenguitar » Thu May 09, 2019 12:23 pm

That all sounds eminently sensible. It's frustrating, but I think you're doing the right thing.

Andy :beamup:
User avatar
zenguitar
Moderator
Posts: 9142
Joined: Thu Dec 05, 2002 1:00 am
Location: Devon
When you see a fork in the road, take it.
Yogi Berra

Re: Odd fuse blowing. iMac 2010

Postby ef37a » Thu May 09, 2019 1:59 pm

zenguitar wrote:That all sounds eminently sensible. It's frustrating, but I think you're doing the right thing.

Andy :beamup:


Indeed^.
Don't know macs but is the PSU integrated with the main PCB? That is how VCRs went and they were buggers to fix.
Philips were the only good guys that I remember in that the PSU was in a slim, tinplate can. The trouble was they did not go the last half inch and supply as a service replacement but sent you a "blow up kit" a bag of components and mods that took a good two hours to change!

Dave.
ef37a
Jedi Poster
Posts: 10377
Joined: Mon May 29, 2006 12:00 am
Location: northampton uk

Re: Odd fuse blowing. iMac 2010

Postby DAGGILARR » Thu May 09, 2019 2:04 pm

It is replaceable, but not easily.
User avatar
DAGGILARR
Frequent Poster
Posts: 758
Joined: Wed Sep 22, 2010 12:00 am
Location: Exeter, Devon.
iMac 27" i7 2.9gh 2010 12GB ram, Focusrite Pro24DSP.

Re: Odd fuse blowing. iMac 2010

Postby Folderol » Thu May 09, 2019 2:28 pm

My guess (apart from a most likely faulty PSU) would be one of the EMI filter caps arcing over. They might be either before or after the the power switch.
User avatar
Folderol
Jedi Poster
Posts: 8263
Joined: Sat Nov 15, 2008 1:00 am
Location: The Mudway Towns, UK
Yes. I am that Linux nut.

Re: Odd fuse blowing. iMac 2010

Postby ef37a » Thu May 09, 2019 2:41 pm

Folderol wrote:My guess (apart from a most likely faulty PSU) would be one of the EMI filter caps arcing over. They might be either before or after the the power switch.

Aha! Could be Will. The X or Y rated caps are "self healing" so they can short but then be fine afterwards. Of course, even in sleep mode there is still close to the peak 340V on them.

Dave.
ef37a
Jedi Poster
Posts: 10377
Joined: Mon May 29, 2006 12:00 am
Location: northampton uk

Re: Odd fuse blowing. iMac 2010

Postby DAGGILARR » Thu May 09, 2019 3:33 pm

ef37a wrote:
Folderol wrote:My guess (apart from a most likely faulty PSU) would be one of the EMI filter caps arcing over. They might be either before or after the the power switch.

Aha! Could be Will. The X or Y rated caps are "self healing" so they can short but then be fine afterwards. Of course, even in sleep mode there is still close to the peak 340V on them.

Dave.

Would fixing that require replacing the power supply?
User avatar
DAGGILARR
Frequent Poster
Posts: 758
Joined: Wed Sep 22, 2010 12:00 am
Location: Exeter, Devon.
iMac 27" i7 2.9gh 2010 12GB ram, Focusrite Pro24DSP.

Re: Odd fuse blowing. iMac 2010

Postby ef37a » Thu May 09, 2019 5:46 pm

DAGGILARR wrote:
ef37a wrote:
Folderol wrote:My guess (apart from a most likely faulty PSU) would be one of the EMI filter caps arcing over. They might be either before or after the the power switch.

Aha! Could be Will. The X or Y rated caps are "self healing" so they can short but then be fine afterwards. Of course, even in sleep mode there is still close to the peak 340V on them.

Dave.

Would fixing that require replacing the power supply?

I would not think so. Have to get it out and have the correct capacitor fitted and have a good look for other damage and, because it is a mains side repair it will need a PAT cert.

Dave.
ef37a
Jedi Poster
Posts: 10377
Joined: Mon May 29, 2006 12:00 am
Location: northampton uk

Next

Who is online

Users browsing this forum: No registered users