Author Topic: measuring resistance of resister after it's soldered to PCB board  (Read 1342 times)

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Offline helmetTopic starter

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This is my first electronics kit project:  the Noise Toaster

http://musicfromouterspace.com/index.php?MAINTAB=SYNTHDIY&PROJARG=NOISETOASTER/NOISETOASTER.php&CATPARTNO=NOISETOASTERPCB

I bought the kit, which includes the PCB board and all of the components.  I believe that I followed the instructions correctly when soldering the components (see the attachments).   The instructions have tests to complete to make sure that everything is working, and some of the tests are failing.   Im following some of the troubleshooting tips, but they havent really helped.   Now Im taking my multimeter and measuring the resistance of all of the resistors installed on the PCB board.  Most of the soldered resisters show the same resistance as before they were soldered.  For instance, a 1M Ohm resister measures 1M Ohm resistance before soldering it to the PCB and after soldering it to the PCB it still measures 1M.  But some soldered resisters do not show the same resistance as before they were soldered.  For instance, a 100K resister shows 100K resistance before soldering, but 33K resistance after soldering it to the board.   I have removed one resister on the board  and replaced it twice with a new one.  For instance, the 100K resister is soldered to the PCB, but only shows 33K resistance after being soldered.  I removed this resister and replaced it with another new 100K resister, and it still shows 33K after soldering.   Have I damaged the PCB board?   Do I just not know how to measure the resistance of a resister after its soldered to a PCB board?  (see attachment)  thanks!   
 

Offline Shock

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Re: measuring resistance of resister after it's soldered to PCB board
« Reply #1 on: July 11, 2019, 02:29:39 am »
This is quite normal, for measuring components in circuit if you get an unexpected measurement assume there is at least one or more components in parallel. So to get around this lift one of the component legs or completely remove it from circuit to measure it out of circuit.
Soldering/Rework: Pace ADS200, Pace MBT350
Multimeters: Fluke 189, 87V, 117, 112   >>> WANTED STUFF <<<
Oszilloskopen: Lecroy 9314, Phillips PM3065, Tektronix 2215a, 314
 

Offline chancs

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Re: measuring resistance of resister after it's soldered to PCB board
« Reply #2 on: July 11, 2019, 03:00:36 am »
Resistors aren't that easy to damage. Instead of checking their value, I would go through all the active components, making sure they have the correct part number. Also, double check and see if you have soldered all the joints.
 

Offline austfox

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Re: measuring resistance of resister after it's soldered to PCB board
« Reply #3 on: July 11, 2019, 04:25:55 am »
From the overlay the resistor directly below X16 and X20 should be 75K, but it looks like you have a 10K in there.
 

Offline ArthurDent

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Re: measuring resistance of resister after it's soldered to PCB board
« Reply #4 on: July 11, 2019, 01:48:20 pm »
That definitely is a 10K not a 75K, plus it has been damaged.

From the looks of some of the solder joints it looks like the joints weren't heated enough to let the solder flow smoothly and there are globs of solder just sitting on some pads and some component leads look dry. You may have bad solder connection in several areas.
 


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