What equipment??

[Behemot]

Re: What equipment??

Most meters do not measure 10 uV, that's what I am talking about.

What is the voltage? How you connect it? Where you connect it? Details!

[SteveNielsen]

Re: What equipment??

That's true. Mine only goes down to 200mV with one decimal so the lowest voltage it can measure is 100uV. However other meters that have .00 resolution could detect a change of 10uV.

So the other question is, what meter are you using?

[Behemot]

Re: What equipment??

Meter is the least of my problem, how does the whole procedure work?

[stj]

Re: What equipment??

he is probably forcing a few volts into the board at a fixed current, then looking for the component with the highest volt-drop across it.

[rievax_60]

Re: What equipment??

I use a Fluke 87v. It has 10uV resolution on its mV range and with the meter in Hi Res mode.
I will make a drawing to show how the method works.

[rievax_60]

Re: What equipment??

Here is the drawing that explains the method and a link to the photo of the example. https://www.badcaps.net/forum/attach...2&d=1393066453

[Behemot]

Re: What equipment??

Yeah but what do you use, adjustable PSU? Voltage and current?

[rievax_60]

Re: What equipment??

So far I have been doing ok at 0.5A, it can be higher. My power supply only has adjustable
voltage so I set it to about 0.5v and put a 1 ohm resistor in series with it that gives the 0.5A current into the shorted rail.
Most linear power supplies as mine is, usually run at high temperature when loaded at low output voltage setting. This is the main reason that I do the testing at 0.5A.

[vinceroger69]

Re: What equipment??

ive just been wtching this video on youtube leakseeker 89 does look ok
https://www.youtube.com/watch?v=BUyEe8G50D4

[Behemot]

Re: What equipment??

[budm]

Re: What equipment??

Shorts finders:
http://www.linear.com/solutions/5297

http://www.edn.com/design/pc-board/4...uses-low-power

http://www.edn.com/design/test-and-m...acer-technique

http://www.edn.com/design/test-and-m...circuit-tracer

http://www.hobbyprojects.com/test_ge...on_tester.html

https://cdn.badcaps-static.com/pdfs/...5b14c897b2.pdf

https://cdn.badcaps-static.com/pdfs/...4386c24828.pdf

http://www.eetimes.com/author.asp?se...doc_id=1284424

http://electronicdesign.com/boards/p...it-pin-pointer

http://electronicdesign.com/boards/i...rcuit-detector

http://www.google.com/patents/US8269505

[newtothis]

Re: What equipment??

Ok little help please.

I have borrowed an ESR meter just to see how I get on with it before purchasing one.

Now I need to figure out how to trace a short using it.... cct I am working on is a graphics card... There are 2 8 pin connectors for the power... There are 2 fuses per connector. 1 Connector has both fuses open the others are closed. So obviously its the one with the busted fuses I need to figure out.

Where do I put the meter lead to start with?
Also how do I know where to use the other lead going around the cct, Don;t have schematic so no idea what components to check at.

[budm]

Re: What equipment??

Using ESR to locate shorted circuit is not really going work if the circuit has a bunch of cap in parallel between the two points you are testing, ESR meter is an AC Ohm meter.
Just do this, get yourself a 1000 Ohms resistor connected in parallel with 1000uF LOW ESR cap, then take the reading and see what you get with that ESR meter, it will show <1 Ohm.

[newtothis]

Re: What equipment??

So basically it aint gonna work?

[newtothis]

Re: What equipment??

My understanding was that of course even traces have resistance... So using an ESR capable of 1000th of an ohm it is possible to see even the slightest change in resistance... The closer you get to the short the lower its resistance even at 0.001 differences

[budm]

Re: What equipment??

Do the experiment by putting a dead short (have some do it without telling you where) on the board and see what you can find, that's how you will build up the technique on finding shorts.

[newtothis]

Re: What equipment??

I am assuming I need to know the route of current to be able to track it down?

[retiredcaps]

Re: What equipment??

This video, starting around the 9:30min mark,

https://www.youtube.com/watch?v=at7GLypcLro

gives you an idea of the resolution you might need to troubleshoot shorts. Notice how fast the Fluke gives a reading. There is at least 5 digits after the 0. For example, 0.09813 ohms.

Accuracy, in this application, isn't as important as resolution.

[retiredcaps]

Re: What equipment??

Here is another technique. I don't have a PSU so I haven't tried this.

http://axotron.se/blog/multimeter-repair/

I do have one multimeter where VCC is shorted to GND and it is maddening trying to find the short. I removed a couple of components that I thought would be the most likely culprits, but I failed. I also don't have a multimeter with low ohm resolution like the one in the above video.

[retiredcaps]

Re: What equipment??

@newtothis, one more idea.

If you are professional tech, you might want a thermal image camera/device in your toolkit? They have dramatically dropped in price and there are even attachments for the smartphone. I believe the attachments are in the $200 range and standalone models are in the $400 range.

If something is shorted, perhaps the thermal camera can show you the component that is running hot? Touching the components with your finger/hand may not yield anything unless something is obviously scorching hot?