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Electronics repair help. Mystery, ummarked component


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#1 Ravenbar

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Posted 20 November 2016 - 11:32 AM

I recently acquired a 47" Vizio that has a manufacture date in 2015. It doesn't work. When I got it the standby light comes on but pressing the power button does nothing. I believe the power supply board is the problem but am not 100% sure. The power switch tests as good.

 

During testing on the power supply, I attempted to jump a fuse and managed to short to a neighboring capacitor. I don't think the capacitor was killed as it is a 470v capacitor and 120v are at the fuse.  In the picture is the area of the PCB in question. the short was between the top capacitors top lead and the top of the fuse. I'm not sure what the component connected to that lead is(it's the orange and black thing just above the capacitor) that then connects to a couple diodes and then into the 12v transformer). Since the short, the standby light hasn't even lit.

 

tumblr_ogy7uoaCeC1u130qco2_1280.jpg

 

Trying to identify the orange and black compontnet as I have no idea what it is or how to test it.

 

An entirely new power supply is $80 and I don't want to spend it as I'm not sure that's the original problem.


Edited by hamluis, 20 November 2016 - 12:12 PM.
Moved from Gen Chat to External Hardware - Hamluis.

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#2 Chris Cosgrove

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Posted 20 November 2016 - 06:09 PM

First of all you have almost certainly blown the 15A 250V fuse which is why your lights are not coming on. The capacitor pin you shorted to was at ground potential - 0V - and the fuse would be at supply potential of 120V. You need to replace this fuse. You can test the fuse by checking the voltage at each end. It should read the same. If one end is now at 120 V and the other at 0V it is blown.

 

Be very careful replacing the fuse as it is very close to those capacitors and they can hold a charge for a long time after you switch off and unplug. You may have to use some imagination replacing the fuse as it looks as though it is soldered to the mobo although it may be in a spring loaded holder. One solution may be just to solder another 15A fuse to the existing one.

 

The good news is that you almost certainly have not damaged the capacitors. Electrolytic capacitors tend not 'to go quietly into that long goodnight' - they tend to explode !

 

I am not sure what that double headed orange component is but since it is labelled 'FB603' and the 15A fuse is labelled 'F601' it is probably some sort of fuse.

 

One question - why were you trying to 'jump' the fuse, was it already blown ?  If it was this suggests there is some serious electrical fault elsewhere in this equipment and you will need to identify that before you have any chance of success.

 

Chris Cosgrove



#3 Ravenbar

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Posted 20 November 2016 - 06:31 PM

First of all you have almost certainly blown the 15A 250V fuse which is why your lights are not coming on. The capacitor pin you shorted to was at ground potential - 0V - and the fuse would be at supply potential of 120V. You need to replace this fuse. You can test the fuse by checking the voltage at each end. It should read the same. If one end is now at 120 V and the other at 0V it is blown.

 

Be very careful replacing the fuse as it is very close to those capacitors and they can hold a charge for a long time after you switch off and unplug. You may have to use some imagination replacing the fuse as it looks as though it is soldered to the mobo although it may be in a spring loaded holder. One solution may be just to solder another 15A fuse to the existing one.

 

The good news is that you almost certainly have not damaged the capacitors. Electrolytic capacitors tend not 'to go quietly into that long goodnight' - they tend to explode !

 

I am not sure what that double headed orange component is but since it is labelled 'FB603' and the 15A fuse is labelled 'F601' it is probably some sort of fuse.

 

One question - why were you trying to 'jump' the fuse, was it already blown ?  If it was this suggests there is some serious electrical fault elsewhere in this equipment and you will need to identify that before you have any chance of success.

 

Chris Cosgrove

 

I was thinking the orange component was a fuse at first but why put 2 fuses in line. The output of the 15a fuse traces into the orange component.

 

As far I could tell the fuse wasn't blown as the continuity test on my multimeter beeped when I touched each end of the fuse. I still wasn't sure the fuse wasn't blown as as electricity requires a complete circuit and the signal could have found its was through another path between the 2 points(unlikely but possible if something else was messed up.) That's why I attempted to jump the fuse, to see it it actually was blown by giving the electricity a path around.


Edited by Ravenbar, 20 November 2016 - 06:32 PM.

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#4 Ravenbar

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Posted 20 November 2016 - 06:51 PM

Just may have identified the orange thing. Per this wikipedia article( https://en.wikipedia.org/wiki/Reference_designator ), the FB designation stands for a ferrite bead.

 

I do see a couple pictures that look similar for double headed ferrite bead inductor. .


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#5 Platypus

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Posted 20 November 2016 - 08:50 PM

FB603 is indeed just a loop of wire through two ferrite beads. The orange is adhesive to stop the beads vibrating under current and possibly making the PSU noisy.

Also note that F601 is a 5A delay (Time) fuse, hence the label T5A, easily mistaken for 15A. It would need to be replaced with the same fuse type with solder leads - soldering onto end caps is often not successful, especially with a delay fuse.

If you're lucky, replacing the fuse will get you back to the original state and let you resume the attempt at a diagnosis. A PSU not starting from standby can have several causes, a common one is deterioration of electrolytic capacitors on the board. Larger ones are an obvious candidate, but non-starting can result from a faulty kick-start capacitor, often a small one around 47uF in the PSU's control circuitry.

Failure to start up from standby can also result from a faulty control button PCB, which typically also contains the R/C receiver, or in some designs where the startup signal is passed through the mainboard control microprocessor, a mainboard fault.
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#6 Chris Cosgrove

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Posted 21 November 2016 - 07:45 PM

@Platypus #5

 

Thanks for the correction - your eyesight is obviously better than mine !  I did think 15A was a rather high value for the purpose but I couldn't make it out as a 'T'. A 5A delay or slow-blow fuse makes much more sense in the application - a maximum power draw of 550W rather than 1650W.

 

Chris Cosgrove






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