How do we check IC on the PCB working or not? - Page 1
Forum section: electronics / general

author: aarvy
author_rank: Newbie
timestamp: July 07, 2014, 05:28:33 am
content: Hello,How can I check that some ICs on PCB works properly or not? Can I turn off the power supply and then by giving necessary inputs and checking outputs? My PCB contains ARM Processor and few Op-amp ICs. I need to check Op-amp IC. I do not have any other testing equipments.

author: David_AVD
author_rank: Super Contributor
timestamp: July 07, 2014, 05:40:13 am
content: Wave a dead fish over it?I think you'll need to supply more details to get a sensible answer.

author: Skimask
author_rank: Super Contributor
timestamp: July 07, 2014, 05:44:18 am
content: Quote from: David_AVD on July 07, 2014, 05:40:13 amoooo..... I like that. Going to try that next time I've got a problem.Now...where to find dead fish....

author: aarvy
author_rank: Newbie
timestamp: July 07, 2014, 05:53:42 am
content: Well, PCB has few ICs ( Op-amps, Driver, Voltage regulators etc). Now I want to check the IC is in working condition or not.Problem: IC is already connected to other ICs on the board. If I will give some INPUT to IC and then check OUTPUT of the IC, can I check this way? ( What if current would flow from this IC to the other part of the PCB ?!)

author: tautech
author_rank: Super Contributor
timestamp: July 07, 2014, 06:01:32 am
content: You could try the "razor blade" technique on individual IC's.Slice signal path tracks (in & out), provide test signal and measure output.Solder over slice when the problem is fixed.

author: Dago
author_rank: Frequent Contributor
timestamp: July 10, 2014, 06:59:22 am
content: Usually something like this is taken in to account when designing the prototype. Putting resistors/jumpers on lines so you can desolder them and feed a different signal. Also putting in a ton of test pads never hurts.

author: rob77
author_rank: Super Contributor
timestamp: July 10, 2014, 07:09:19 am
content: Quote from: Skimask on July 07, 2014, 05:44:18 ami think the best source for extremely dead fish is this(extremely dead - judged by the smell (stench?) )http://en.wikipedia.org/wiki/Surstr%C3%B6mmingbut to the OP's question - just measure the in/out voltages of the opamps in-circuit and compare the readings to the expected values.

author: owiecc
author_rank: Frequent Contributor
timestamp: July 10, 2014, 07:15:19 am
content: Quote from: aarvy on July 07, 2014, 05:28:33 amTurning the power on helps with debugging. Checking an opamp is quite straight forward. Check if correct voltage is present on power pins. Locate the inputs and check if the voltage difference is zero with a multimeter. Check also is input voltages are within the acceptable range.

author: Bassman59
author_rank: Super Contributor
timestamp: July 10, 2014, 09:29:31 pm
content: Quote from: aarvy on July 07, 2014, 05:28:33 amWell, if you want to test an op-amp, the usual thing to do is to give it an input signal and look at both the input and the output on an oscilloscope.

author: jamesglanville
author_rank: Contributor
timestamp: July 10, 2014, 10:24:56 pm
content: Can you not just write some test code to run on the ARM? It should be quite possible to get the ARM to send a range of signals to the opamps and then probe the outputs with an oscilloscope.

author: David_AVD
author_rank: Super Contributor
timestamp: July 10, 2014, 10:44:23 pm
content: The OP is possibly another "post and run" guy. No easy instant result and they haven't been back since the day of posting. Seems to be a few of those lately.

author: Bassman59
author_rank: Super Contributor
timestamp: July 11, 2014, 09:44:41 pm
content: Quote from: David_AVD on July 10, 2014, 10:44:23 pmHe got an answer he didn't like. Hedidsay, "I do not have any other testing equipments," and of course every reasonable response said, "Look at it with your oscilloscope."

author: Skimask
author_rank: Super Contributor
timestamp: July 12, 2014, 03:37:13 am
content: Quote from: David_AVD on July 10, 2014, 10:44:23 pm"a few" is the understatement of the year!

author: Smokey
author_rank: Super Contributor
timestamp: July 12, 2014, 05:27:25 am
content: This is assuming NO other equipment....Test #1) Visually inspect. Does it have a big hole burned in the top of the package?Test #2) Touch test. Power up the board and tough the part with your finger. Did it burn the hell out of you?Passing these tests doesn't guarantee a functional part... But failing them is probably a bad sign