Why this post ?
many requests from friends and newbies asking how to use ESR meters for faultfinding.
to highlight the instrument limitations and share my thoughts and workflow .
I use ESR meters to measure the caps precisely in-circuit ....typically down to 0.05R
If the value looks odd , i huntron it , to find out if there are any other components connected and interfering with it
It helps if you have 2 similar boards to compare the values.
Without schematics , comparisons are my preferred choice when troubleshooting .
I also use ESR meters to see the values out of circuit.
i use a model which measures both capacitance and ESR together. To check for bad caps before putting them into a circuit. Some suppliers may sell bad caps or caps which have been stored for a long time. There are date codes on some Ecaps.But testing them is the best way to know if they are good before putting them into a circuit.
Here is a practical exercise to learn more ...
Try this to learn limitations of ASA and ESR when troubleshooting .
Get a few ceiling Led light driver PCBs .5 or 6 would be Good for studying Ecaps in-circuit.
If you have a tracker and ESRmeter, Use both on the ecaps. Those caps are in hostile environment (high temp) and fail often .
You need to troubleshoot with power -off ( dangerous to probe components in power-on state)...advantage of using Huntron power-off method when troubleshooting
This situation is often what we are faced with when troubleshooting pcbs:-
No schematics.
Ecaps ,diodes,R ,IC, transformers connected together in- circuit .
Lots of VI combinations to "see" ( diodes+caps , diodes +R, IC+R ...)
Simple circuit to learn VI and easy to get 2 similar PCBs.
Easy to remove Ecaps and study performance issues (ie test bed to study manufacturer's claims on performance ).
Replace a few ecaps with higher quality ones and put lights back into operation. If lights fail ,you can see the failures....When you switch it on/off ,it does not light or Time lags ,means Ecaps are beginning to fail or failed.
Test ecaps again.( In and out circuit with both equipment ).The ecaps should have increased in esr .Small increases can be seen by the esr meter but not with the huntron.
You should see the limitation of each.
NOTICE
If VI signatures look the same , it should be good , safe to power -on the PCB.
In conclusion , know the limitations of your tools , spend your time studying which components fail and practice ,practice ,practice to improve your observation skills and you will be successful.
Happy troubleshooting .Repairing more helps the environment
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