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Old 13th July 2010, 02:09 PM   #51
Cristi is offline Cristi  Europe
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It might be a cold start overcurrent which could kill the thermistor. that can explain the noise and the fact that the fuse is not burned. can you measure the thermistor, with a multimeter, should have about 10R when is cold. make sure that you disconnect everything before measure. i wont' guide you to measure anything else which implies to connect the smps to live mains. if you cannot find the problem, just send me back and i will replace it.
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Old 13th July 2010, 02:31 PM   #52
alkasar is offline alkasar  France
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Quote:
Originally Posted by Cristi View Post
It might be a cold start overcurrent which could kill the thermistor. that can explain the noise and the fact that the fuse is not burned. can you measure the thermistor, with a multimeter, should have about 10R when is cold. make sure that you disconnect everything before measure. i wont' guide you to measure anything else which implies to connect the smps to live mains. if you cannot find the problem, just send me back and i will replace it.
thanks for the help. referring to the pcb, could you tell me which one is the thermistor ?


edit : I looked again the board carefully: it seems that a small component (R2 on pcb) is blown.

Click the image to open in full size.

Last edited by alkasar; 13th July 2010 at 02:54 PM.
 
Old 13th July 2010, 03:10 PM   #53
Cristi is offline Cristi  Europe
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the thermistor is R2, exactly the one which you said. in the attached image, has the oblong footprint just under the rectifier bridge and C24.
replace the thermistor with a new one, same value, and for better reliability you can consider a bigger size. the value is 10R. the code for a bigger one is NTC 10D-13. after you replace, leave about 12-15mm long legs from the pcb to allow heat dissipation without overheating the board. in normal working conditions the thermistor gets very hot, over 60*C.
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Old 13th July 2010, 04:54 PM   #54
alkasar is offline alkasar  France
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Quote:
Originally Posted by Cristi View Post
the thermistor is R2, exactly the one which you said. in the attached image, has the oblong footprint just under the rectifier bridge and C24.
replace the thermistor with a new one, same value, and for better reliability you can consider a bigger size. the value is 10R. the code for a bigger one is NTC 10D-13. after you replace, leave about 12-15mm long legs from the pcb to allow heat dissipation without overheating the board. in normal working conditions the thermistor gets very hot, over 60*C.
ok will do.
10R Thermistor is actually not that easy to find I could not find your exact reference.
I've found some at this website in english at farnell

They differ by the current and by "BETA value" which I have no clue what it means .
Would this one do ?
Code:
EPCOS B57238S100M 
    * THERMISTOR, NTC, 10R, 5A
    * Thermistor Type:NTC
    * Resistance:10ohm
    * Beta Value:1208
    * Beta Value Lower Limit Temperature:25C
    * Body Diameter:16mm
    * Case Style:Radial
    * Lead Length:32mm
    * Lead Spacing:7.5mm
    * Max Current:5A
    * Max Operating Temperature:170C
    * Max Power Dissipation Ptot:3.9W
    * Operating Voltage:265V
    * Resistance Tolerance: 20%
    * Series:B57238
    * Temperature Upper Limit, Beta Value:100C
16mm is much bigger than the current one but I should be able to make it fit. There are smaller ones; but they would only support 3A.
 
Old 14th July 2010, 02:38 PM   #55
Cristi is offline Cristi  Europe
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The thermistor used for this smps is not a "sensitive" choice. in fact, any thermistor which have nominal resistance at 25*C between 5 to 10R and can withstand at min. 3A can be used. the size should be between 9 to 13mm, bigger one will not fit on the tight space.
i just narrow the search and there are 3 types which can be used.
Your Search Results | Farnell United Kingdom
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Old 14th July 2010, 02:47 PM   #56
alkasar is offline alkasar  France
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Quote:
Originally Posted by Cristi View Post
The thermistor used for this smps is not a "sensitive" choice. in fact, any thermistor which have nominal resistance at 25*C between 5 to 10R and can withstand at min. 3A can be used. the size should be between 9 to 13mm, bigger one will not fit on the tight space.
i just narrow the search and there are 3 types which can be used.
Your Search Results | Farnell United Kingdom
thanks. for some reason, the link does not work on my side. Could you give me the part numbers ?
 
Old 14th July 2010, 03:40 PM   #57
Cristi is offline Cristi  Europe
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Join Date: Dec 2008
Location: Dortmund+Shenzhen
i will post the direct link to the parts: http://uk.farnell.com/ge-sensing-the...tor/dp/1707218
AMETHERM|SL10 10002|NTC Thermistor | Farnell United Kingdom
be very careful when you install the new thermistors. after plug-in the smps the big capacitor will be charged at +300V, then will take few minutes to discharge. wait until is completely discharged, and only then can work with the board.
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Old 14th July 2010, 03:40 PM   #58
Cristi is offline Cristi  Europe
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Join Date: Dec 2008
Location: Dortmund+Shenzhen
i will post the direct link to the parts: http://uk.farnell.com/ge-sensing-the...tor/dp/1707218
AMETHERM|SL10 10002|NTC Thermistor | Farnell United Kingdom
be very careful when you install the new thermistors. after plug-in the smps the big capacitor will be charged at +300V, then will take few minutes to discharge. wait until is completely discharged, and only then can work with the board.
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Old 14th July 2010, 04:25 PM   #59
alkasar is offline alkasar  France
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Join Date: Jan 2009
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Quote:
Originally Posted by Cristi View Post
i will post the direct link to the parts: GE SENSING / THERMOMETRICS|CL-120|NTC Thermistor | Farnell United Kingdom
AMETHERM|SL10 10002|NTC Thermistor | Farnell United Kingdom
be very careful when you install the new thermistors. after plug-in the smps the big capacitor will be charged at +300V, then will take few minutes to discharge. wait until is completely discharged, and only then can work with the board.
ok. thanks for the advice : good for my health !
I'll pick this one : similar or better than the suggested. A bit more expensive, but available here in Europe to avoid the 16GBP shipment costs from the US!
EPCOS|B57235S100M|THERMISTOR, NTC | Farnell United Kingdom
I'll let you know the result of the surgery.
 
Old 14th July 2010, 04:58 PM   #60
Cristi is offline Cristi  Europe
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Join Date: Dec 2008
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if you can't find-it or is expensive, just let me know and i will send you without charge by letter.
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