Re: 12V, 1.5A PSU Adaptor Inductor Overheating
With psu reassembled and original modem load the case temperature is warm but not hot. The CM choke must have always been running hot and with time destroyed itself.
To minimise this recurring I shall unwind half the turns from each coil of the choke.
A big thank you to every-one who contributed to this Sherlock Holmes story. I have learnt much about the switch mode psu and the willingness of others to help solve problems....
mindmend
Member
Last Activity: 01-16-2020, 04:16 PM
Joined: 01-12-2020
Location: Queensland
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Re: 12V, 1.5A PSU Adaptor Inductor Overheating
It did significantly change. On opening the case the original choke had obviously overheated and was getting hotter than 70C but I didn't measure that - I just replaced it.
I'm wondering if in this design the choke always ran hot could it have broken down and seriously overheated.
I don't know normally how hot the choke gets with this design, which makes me wonder if 70C is normal. That's what I was hoping someone could give an opinion on.
I will reassemble the case and power the modem like before that's...Last edited by mindmend; 01-16-2020, 02:27 AM.Leave a comment:
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Re: 12V, 1.5A PSU Adaptor Inductor Overheating
[COLOR="RoyalBlue"]Update:[/COLOR]
Sorry Hitto, I should have said no SMD caps in the input rectifier and filter areas.Re: 12V, 1.5A PSU Adaptor Inductor Overheating
[COLOR="RoyalBlue"]Update:[/COLOR]
Sorry Hitto, I should have said no SMD caps in the input rectifier and filter areas.Re: 12V, 1.5A PSU Adaptor Inductor Overheating
[COLOR="RoyalBlue"]Update:[/COLOR]
Sorry Hitto, I should have said no SMD caps...Leave a comment:
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Re: 12V, 1.5A PSU Adaptor Inductor Overheating
[B]On load:[/B]
400mV DC
30mV AC
Off load it's close to zero.
As a last resort I will remove some windings from the choke.Re: 12V, 1.5A PSU Adaptor Inductor Overheating
[B]On load:[/B]
400mV DC
30mV AC
Off load it's close to zero.
As a last resort I will remove some windings from the choke.Re: 12V, 1.5A PSU Adaptor Inductor Overheating
[B]On load:[/B]
400mV DC...Leave a comment:
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Re: 12V, 1.5A PSU Adaptor Inductor Overheating
Removed the white rubbery glue. I don't have an X2 100nF capacitor to hand.
Not mylar, it's a 1nF ceramic disk connected in parallel with the 22uF cap. I will replace and report.
I had already replaced the choke (the original one looked and smelt like it was seriously cooked). The solder joints are good.
There are no SMD capacitors anywhere on the PCB.
The mains input current is 0.037A (not true rms meter) = ~9W.
The output load...Leave a comment:
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Re: 12V, 1.5A PSU Adaptor Inductor Overheating
Yes the choke remains cold off load....Leave a comment:
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Re: 12V, 1.5A PSU Adaptor Inductor Overheating
Yes that's right Hitto, the choke is connected after the bridge rectifier.
The thought of bypassing the choke did come to mind. I haven't done that (yet!) for these reasons:[LIST][*]Something changed - the PSU did not previously run hot.[*]Switching noise injecting back into the mains supply.[*]Reduced protection from incoming voltage spikes on the mains supply.[/LIST]
My first choice is to find out what caused the psu to suddenly get much hotter than before. And to know what temperature...Leave a comment:
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Re: 12V, 1.5A PSU Adaptor Inductor Overheating
Before, it's only 10uF, the second cap is 22uF after the CM choke. Ripple current will be passing through the choke to the second cap.
I don't have an oscilloscope so cannot see the ripple....Leave a comment:
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Re: 12V, 1.5A PSU Adaptor Inductor Overheating
The mains input current is 0.037A (meter is not true rms) with the 12V load of 0.7A, sorry for ambiguity.
The voltage on the caps is 329V, with mains input of 239V AC.
This is useful info, in this case the rise above ambient is about 50C but that's under half load.
There is an NTC, it is running just warm. All other components are running warm ~38C. Except the switching (FET?) on the heatsink it's running about 45-50C with 12V loaded to 0.7A....Leave a comment:
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Re: 12V, 1.5A PSU Adaptor Inductor Overheating
Thank you for your reply.
The four rectifier diodes measure correctly. The cap on the input (output of the bridge rectifier) to the inductor coils is 10uF 400V the output of the filter has a cap of 22uF 400V.
The mains input connects through a fuse directly to the bridge rectifier, I don't see anything to limit the current into the filter inductor.
I have tried putting a 33uF cap in place of the 10uF to get less ripple before the filter but this experiment didn't seem to change the...Leave a comment:
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Re: 12V, 1.5A PSU Adaptor Inductor Overheating
[B][COLOR="RoyalBlue"]Update:[/COLOR][/B]
Replacing the reservoir cap connected to the bridge rectifier has not reduced the temperature of the inductor.Re: 12V, 1.5A PSU Adaptor Inductor Overheating
[B][COLOR="RoyalBlue"]Update:[/COLOR][/B]
Replacing the reservoir cap connected to the bridge rectifier has not reduced the temperature of the inductor.Re: 12V, 1.5A PSU Adaptor Inductor Overheating
[B][COLOR="RoyalBlue"]Update:[/COLOR][/B]
Replacing the reservoirLeave a comment:
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12V, 1.5A PSU Adaptor Inductor Overheating
This 12V, 1.5A 240V mains adaptor is being used to power an adsl modem router. Usually it runs quite cool when it changed and I noticed the case was getting excessively hot.
Opening the case revealed the mains input filter inductor is getting far too hot. I replaced it. The replacement also gets hot but not as hot, it reaches 70C after being on for 10 mins supplying 0.7A (cools down off load) - this is with the case open. See attached images.
I don't know how hot is normal for this inductor, please anyone with experience I would value your opinion.
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Re: New Members - please post your introductions here
Good day one and all.Leave a comment:
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