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Corsair Grey Label CX750M Burning Smell [Fault Finding And Repair]

iamdarkyoshi
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Looking at that I'd be thinking it may have been bad / wrong ferrite material, even if the ferrite was ok theres a good change the curie temperature has been exceeded so if you're rewinding take one from a scrap supply.

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It's not the wrong material.  It was just wound poorly.

 

These aren't made by ten year olds in Summer Camp... although the results may make some of us think they might be.

 

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42 minutes ago, paddyponchero said:

Looking at that I'd be thinking it may have been bad / wrong ferrite material, even if the ferrite was ok theres a good change the curie temperature has been exceeded so if you're rewinding take one from a scrap supply.

I found a new one to use on this, its the exact same size and weight.

 

Both of them stick to a magnet, so the original toroid was probably okay.

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I'll be following this for a while. Interesting.

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36 minutes ago, jonnyGURU said:

It's not the wrong material.  It was just wound poorly.

 

These aren't made by ten year olds in Summer Camp... although the results may make some of us think they might be.

 

It was made by kids in a sweatshop in Bangledesh with no fire exit/protections

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@jonnyGURU

 

Not gonna lie, I'm a bit stumped. I wound the transformer just like I originally THOUGHT it was (both windings have 12 turns, and they both go the same way) and after reassembling the unit, I connected it to my power meter, and it started at 26w and quickly shot for >150w and then shut off. All that was connected is a jumper from PSON to GND.

 

I tried it multiple times with the same result.

 

I took it apart and the inductor felt hot, so its definitely what is dissipating the power.

 

But why? I measured between primary and secondary in circuit and didn't find a short.

 

Did I get my phasing wrong, do I need to swap the polarity of one winding, or is there more at fault? This thing's beefy winding comes from the "sync card" and out to the 12v filter caps. I quickly checked over the sync card and found no shorted silicon devices.

 

The plot thickens.

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Another similarly baked one:

r5mIY0U.jpg

 

The corsair design is virtually identical to the thermaltake one and that doesn't have the same terrible reputation.

Corsair, minty green core looks like micro metals powdered iron but could be anything really.

cx750.jpg

 

Thermaltake

CWT_PUQ-B.jpg

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Looks like a lower wattage CX vs. a higher wattage Thermaltake Smart.  Is that an 850W Thermaltake?  Looks the same as the CX850 inside.

 

Also less Thermaltake examples out there because there are less in circulation.

 

There must be another problem with the PSU and the burning choke is the result, but not the cause.

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24 minutes ago, jonnyGURU said:

Looks like a lower wattage CX vs. a higher wattage Thermaltake Smart.  Is that an 850W Thermaltake?  Looks the same as the CX850 inside.

Its a CX750M. 

 

25 minutes ago, jonnyGURU said:

There must be another problem with the PSU and the burning choke is the result, but not the cause.

Thats what I'm worried about...

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53 minutes ago, iamdarkyoshi said:

Its a CX750M. 

 

Not you.  The post above me.  He posted a picture of two PSUs, but the bottom one looks higher wattage than the top one.

 

I didn't quote his post because I didn't want a copy of all of his images in my post.

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10 hours ago, paddyponchero said:

The corsair design is virtually identical to the thermaltake one and that doesn't have the same terrible reputation.

Both are CWT PUQ-B models, so will look very similar, because they are both slight alterations of the same thing.

 

Much more corsair CX750/CX750M/850M exist than that Thermaltake whatever it is, therefore more well known, so more room for a bad rep (that it didn't deserve IMO, essentially the PUQ-B models).

10 hours ago, paddyponchero said:

 

 

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  • 1 month later...

Did op make any progress I have another baked cx750m here on my office floor, owner reported burning smell. 

 

cx750m.jpg.171057c937c017163c4f7330ff68016e.jpg

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1 minute ago, paddyponchero said:

Did op make any progress I have another baked cx750m here on my office floor, owner reported burning smell. 

 

cx750m.jpg.171057c937c017163c4f7330ff68016e.jpg

Looks like the exact same fault.

 

My rewound coil got very hot very quickly, so either I got my phasing wrong or the board that drives it is faulty. @jonnyGURU Any advice?

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Man these CX units...

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I wonder are the serial number sequential. Serial number on this one is 14257113000008843465. Did you try running it with the modular board disconnected.

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34 minutes ago, paddyponchero said:

I wonder are the serial number sequential. Serial number on this one is 14257113000008843465. Did you try running it with the modular board disconnected.

I'm almost considering trying it with the thin winding on the transformer disconnected

 

The other one is just in series with the 12v output

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2 hours ago, paddyponchero said:

I wonder are the serial number sequential. Serial number on this one is 14257113000008843465. Did you try running it with the modular board disconnected.

So that would be 25th week of 2014.  Even older than OP's, but probably the same inductor factory:  A really shitty one that Corsair has told CWT not to use any more.

 

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2 hours ago, iamdarkyoshi said:

I'm almost considering trying it with the thin winding on the transformer disconnected

 

The other one is just in series with the 12v output

Second winding is the -12v, not sure if its monitored by the supervisor chip I'd have to check the datasheet.

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3 hours ago, paddyponchero said:

Second winding is the -12v, not sure if its monitored by the supervisor chip I'd have to check the datasheet.

Nope, there aren't any that provide a -12V input.

But you don't need it anyway for modern PCs I think...


The last things that might need it are Audio Chips and maybe the old PCI slot...

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  • 5 months later...

exact same issue here. the same inductor overheating on cx750m. in my case the fan is also not working. i measured 100+ deg celsius on the inductor, nothing else is anywhere close heated up on the board.

 

can you point me what the specs of that inductor is? and what else might be causing the inductor to heat up? would changing the inductor with a new one suffice to solve the issue?

 

what is the final situation of the owners in the thread?

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  • 1 year later...

Hello, I also present the same problem but different version, it is a corsair CX750 (not modular). In the end, was there any solution to the problem?

 

here some captures:

 

https://imgur.com/a/FwMQlae

 

PD, In the following weeks I will post my progress with the  power supply.

 

spacer.png

P1040922.JPG

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  • 5 months later...

Thought I'd de-necro this thread for a laugh.. (sorry ?).. But I have a CX750 with the same issue! It worked great for a couple of years, smelled strange for two weeks (waiting for it to die..haha!) then shut off during benchmarking, completely dead.. After two years of meaning to RMA it but being busy and having replaced it, decided to void the no longer active warranty and find out.. To my surprise it had started working again, powered up a crap AMD FX test machine for a good 15 minutes, funky smell and heat returned, so pulled the plug. Same result, cooked inductor and a very hot Sync card. I'll investigate tomorrow, I need bed! Be nice to turn it into a bench supply, I could run some car amps/head unit or two from it, or a couple of Xbox One/360s lol

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  • 1 month later...

Suppose everyone gave up on this, but i finally got around to removing the old coil after stripping another dead PSU (500W OCZ piece of crap..) to harvest parts. The coil from that obviously can't be used in this one, as it seems to be creating 5V and -12V (has 3 different windings, very thin one going the same direction but crossed over to the board, single thicker one with fewer turns and two together with more turns (about 12, the same) but it's really tempting to install it in place of the burned one just for a laugh (and not use the thin one) but, even if it works, something's gonna get the wrong voltage.. Sync card seems fine but i'm suspicious of a near-by diode.. Time to make some smoke!

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  • 3 months later...

Did anyone make any progress on this subject?  I have a CX750M date code 49th week of 2014 that looks just like this.  I'd love to get it fixed.  I hate paying for crappy hardware.

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