good day everyone. i just want to know what method or technic you are using to find short circuit easily and fastest by your thought? please don't mind to share it..
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the best way to find short circuit?
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Re: the best way to find short circuit?
Originally posted by tom66 View PostHigh current from constant current power supply plus freeze spray.
from my understanding, we connect a red probe high current PSU to the "line" ( means live or neutral mains?) and the black probe to ground for a while. release the probes, any warm or hot by touched is the faulty one.. is that right?"There is no shortcut to be successful. No pain, no gain."
Best Regards
Rudi
Thank You
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Re: the best way to find short circuit?
I use 3 amps but if the components are small, 500mA can work. 3 amps makes just about anything get very hot. I only apply the current for half a second, I'm not looking to burn the failed component. If the current is sufficient, the component will get warm, melting the freeze spray, accurately pinpointing the fault. I find that using a finger alone isn't precise enough... you don't actually have great thermal "resolution" on your finger... just enough to tell you if it's hot or cold... freeze spray makes it obvious exactly what is getting hot. Poor man's thermal imaging camera.
It's important that the supply you have or have made limits current non-destructively, i.e. it can safely drive a short. For example, when I short out my power supply set to 2 amps, it becomes a 2 amp constant current source (output voltage nearly zero) and can do so continuously without damage, though it does get rather warm due to the extra heat produced in the power transistors.Last edited by tom66; 09-20-2013, 07:14 PM.Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
For service manual, schematic, boardview (board view), datasheet, cad - use our search.
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Re: the best way to find short circuit?
Originally posted by tom66 View PostI use 3 amps but if the components are small, 500mA can work. 3 amps makes just about anything get very hot. I only apply the current for half a second, I'm not looking to burn the failed component. If the current is sufficient, the component will get warm, melting the freeze spray, accurately pinpointing the fault. I find that using a finger alone isn't precise enough... you don't actually have great thermal "resolution" on your finger... just enough to tell you if it's hot or cold... freeze spray makes it obvious exactly what is getting hot. Poor man's thermal imaging camera.
It's important that the supply you have or have made limits current non-destructively, i.e. it can safely drive a short. For example, when I short out my power supply set to 2 amps, it becomes a 2 amp constant current source (output voltage nearly zero) and can do so continuously without damage, though it does get rather warm due to the extra heat produced in the power transistors."There is no shortcut to be successful. No pain, no gain."
Best Regards
Rudi
Thank You
Comment
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Re: the best way to find short circuit?
One on ground, the other to whichever power input or voltage input is shorted on the board.Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
For service manual, schematic, boardview (board view), datasheet, cad - use our search.
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Re: the best way to find short circuit?
Originally posted by tom66 View PostOne on ground, the other to whichever power input or voltage input is shorted on the board.
maybe i have to get that freeze spray on supply market (store) to get a better result instead using my hand."There is no shortcut to be successful. No pain, no gain."
Best Regards
Rudi
Thank You
Comment
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Re: the best way to find short circuit?
Originally posted by senz_90 View Postaha..!! i am understand clearly now..so the other must be connect to whichever power input predicted short on the board..thank you for advice
maybe i have to get that freeze spray on supply market (store) to get a better result instead using my hand.
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Re: the best way to find short circuit?
Originally posted by rievax_60 View PostBe certain to set the power supply voltage to something lower that the rails's normal operating voltage. This is to avoid causing lots more damage if the short clears itself."There is no shortcut to be successful. No pain, no gain."
Best Regards
Rudi
Thank You
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Re: the best way to find short circuit?
Originally posted by tom66 View PostYes. For example, I'd set it to around 1V.
the other's have a another advice or technic to find the short circuit without wasting the time?? it's so fun to learn about troubleshooting technic..Last edited by senz_90; 09-21-2013, 10:02 AM."There is no shortcut to be successful. No pain, no gain."
Best Regards
Rudi
Thank You
Comment
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Re: the best way to find short circuit?
Some tricks I use for locating shorts:
Inject 1V or so at max. 1 amp (~1watt) and see what is getting warmed up. Higher current can melt thin PCB traces. Usually you can feel the hot spot if you wait a while, or use an IR thermal cam if you have one.
Use a high-resolution multimeter (HP34401 6-1/2 digit) and you can measure μV voltage-drops along PCB traces and wires, to locate the short.
I also lift pins/leads of parts to isolate them. Some boards get hit with overvoltage and many things short, so you can get lost by thinking it's just one bad part.
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Re: the best way to find short circuit?
You do NOT need to lug a power supply around.
The ohm will show a large change when you heat or cool the shorted parts.
With much better resolution the your finger.
You do not need to know or have a schematic to find the power connections in hopes to see a difference in voltage drops.
To find a short or multiple shorts.
Say the 3.3v supply has 4 ohms.
attach your ohm meter to the 3.3 volt line.
And using chilling spray or a heat gun.
The component that causes a change in the ohm is or are most likely at fault.
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Re: the best way to find short circuit?
Originally posted by redwire View PostSome tricks I use for locating shorts:
Inject 1V or so at max. 1 amp (~1watt) and see what is getting warmed up. Higher current can melt thin PCB traces. Usually you can feel the hot spot if you wait a while, or use an IR thermal cam if you have one.
Use a high-resolution multimeter (HP34401 6-1/2 digit) and you can measure μV voltage-drops along PCB traces and wires, to locate the short.
I also lift pins/leads of parts to isolate them. Some boards get hit with overvoltage and many things short, so you can get lost by thinking it's just one bad part."There is no shortcut to be successful. No pain, no gain."
Best Regards
Rudi
Thank You
Comment
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Re: the best way to find short circuit?
Originally posted by shortchange View PostYou do NOT need to lug a power supply around.
The ohm will show a large change when you heat or cool the shorted parts.
With much better resolution the your finger.
You do not need to know or have a schematic to find the power connections in hopes to see a difference in voltage drops.
To find a short or multiple shorts.
Say the 3.3v supply has 4 ohms.
attach your ohm meter to the 3.3 volt line.
And using chilling spray or a heat gun.
The component that causes a change in the ohm is or are most likely at fault."There is no shortcut to be successful. No pain, no gain."
Best Regards
Rudi
Thank You
Comment
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Re: the best way to find short circuit?
4 ohms is what your ohm meter may read read for a typical short cicuirt.
It may read something else.
The point is you will see a large change with your ohm meter monitoring the "shorted" power supply voltage "line" (WHILE THE POWER IS OFF and no external power supply) by chilling the bad part.
The good parts will not change the ohm meter.
Your DMM does not have an ohm setting?
Mine is a Fluke model 16.
I have been using this method for many years now, while other techs lug their power supply around.
Accurate reading on voltage drop means you might notice a dip in voltage.
After probing around 10 accurate voltage reading you notice a dip.
So you remove a 100 pin SMD ic to find that was not shorted
but nearby is a cap that is bad.
You would see a large change in the ohm meter chilling the ic or cap!
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Re: the best way to find short circuit?
You can buy electronic freeze spray for troubleshooting:
http://www.allelectronics.com/make-a...-OZ-CAN/1.html
or use canned air duster upside down to get really cool air.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: the best way to find short circuit?
Originally posted by shortchange View Post4 ohms is what your ohm meter may read read for a typical short cicuirt.
It may read something else.
The point is you will see a large change with your ohm meter monitoring the "shorted" power supply voltage "line" (WHILE THE POWER IS OFF and no external power supply) by chilling the bad part.
The good parts will not change the ohm meter.
Your DMM does not have an ohm setting?
Mine is a Fluke model 16.
I have been using this method for many years now, while other techs lug their power supply around.
Accurate reading on voltage drop means you might notice a dip in voltage.
After probing around 10 accurate voltage reading you notice a dip.
So you remove a 100 pin SMD ic to find that was not shorted
but nearby is a cap that is bad.
You would see a large change in the ohm meter chilling the ic or cap!
what is normal value indicate short on ohm meter, 0 ohm? or is that have not exact value? or i just have to notice a big dip on measurement voltage drop? for example value please between normal and shorty one??"There is no shortcut to be successful. No pain, no gain."
Best Regards
Rudi
Thank You
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