# find faulty capacitor in circuit if there are many

#### Kardo22

Mar 7, 2014
36
Hi
I have a problem.
I have 24V line shorted to ground. I think a shorted capacitor but there are many bypass and decoupling capacitors. How can I find the faulty one?
Is there a solution except to start taking off capacitors 1 by 1?

thanks

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,470
The strategy is "divide and conquer":
Split the line in half (meaning with respect to the number of capacitors half of them on each side of the split. Check each half for the fault.
Split the faulty half line again in half (so you have 2*1/4 of the original line). Check again for the fault.
Continue until the fault is located.

For n capacitors, you will need max. lb(n) splits instead of checking n capacitors (lb = binary logarithm, base 2).

#### shrtrnd

Jan 15, 2010
3,859
If you've got a short, with power input disabled/disconnected,use an ohmeter across each cap to locate the one that's shorted.

#### KrisBlueNZ

##### Sadly passed away in 2015
Nov 28, 2011
8,393
If you've got a short, with power input disabled/disconnected,use an ohmeter across each cap to locate the one that's shorted.
That won't work - they're all in parallel! They will all measure short.

There are ways to do this by passing a current into the short and tracing the voltage drop across the copper traces or the current flow in them, but you need a current tracer or a sensitive voltmeter, and you need to trace the positive and negative tracks. Do some Googling.

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
That won't work - they're all in parallel! They will all measure short.

There are ways to do this by passing a current into the short and tracing the voltage drop across the copper traces or the current flow in them, but you need a current tracer or a sensitive voltmeter, and you need to trace the positive and negative tracks. Do some Googling.

Well, it kinda will.

If you can measure down to milliohms you can measure the resistance of the track or wires. If you can do that, you can search for the point with the minimum resistance and that will be close to your short.

Specialist tools (like a leakseeker, or toneohm, or any of these) are also available as Kris suggests.

#### Colin Mitchell

Aug 31, 2014
1,416
The first things to suspect are transistors, then IC's. I have repaired 45,000 products. Maybe one or two shorted tantalum capacitors in Blaupunkt TV's - but they are the last thing to suspect.

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