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Can SMPS transformer be tested with a oscilloscope

Thread starter #1
Hello everybody .

I have tried different ways to check Smps transformers like the induction meter and its Q parameter.

And read that the ring tester is not accurate to know if the transformer is shorted.


So i have an oscilloscope 20 mhz old school crt. Can this be useful for smps transformers.
 

crutschow

Well-Known Member
Most Helpful Member
#2
Along with a pulse generator, probably.
What are the specifications of the transformer?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
#3
Ring testing is fairly effective for a SMPS TX, and will show if it's got shorted turns - such failures are usually fairly serious . I've repaired thousands of switchmode PSU's over the decades, and to be fair TX failures are pretty rare, there was only a small number of particular types which ever failed.
 
Thread starter #4
Ring testing is fairly effective for a SMPS TX, and will show if it's got shorted turns - such failures are usually fairly serious . I've repaired thousands of switchmode PSU's over the decades, and to be fair TX failures are pretty rare, there was only a small number of particular types which ever failed.
I get to repair some smps welders .
The problem is sometimes i cant find any problem on them so am left with the assumption of having a transformer problem.

I will unsolder one and upload it here this tranformer is switched using a viper20a smps Ic.
Now about the ring tester , does it test all types of smps transformers ?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
#7
Is pulse generator necessary ? Is it possible to apply custom high frequency voltages to the transformer ?
You don't seem to understand what 'ring' means?, it's like striking a bell making it 'ring' - in the same way you apply a brief pulse to an inductor and watch the 'ring' on the scope. Historically it was done using the timebase output of the scope to create the pulse.
 
Thread starter #8
Ring testing should work for any reasonable inductor, obviously the best thing to do is test a good one, and make a record of the result - then compare it to any potentially faulty ones later.
Thanks . I will get one anyways .

So how about the lcr meter with the D ( dissiparion factor ) i have . Can i get the Q parameter just as good as a ring tester ?
 

dr pepper

Well-Known Member
Most Helpful Member
#9
A smps weld set, powered by a viper?, such Ic's were meant for standby supplies in consumer equipment.
Do you mean an inverter weld set with a auxilliary supply controlled by the viper chip.
I wouldnt be over concerned with the Q, an insulation test and a inductance test will give you a good idea on the trans.
Dont do an insulation test in circuit.
 
Thread starter #11
A smps weld set, powered by a viper?, such Ic's were meant for standby supplies in consumer equipment.
Do you mean an inverter weld set with a auxilliary supply controlled by the viper chip.
I wouldnt be over concerned with the Q, an insulation test and a inductance test will give you a good idea on the trans.
Dont do an insulation test in circuit.
Yes its for auxilliary supply .
That welder is dead with some burnt resistors near the viper . I will change them and see what happens.
 
Last edited:
#12
Its more than likely something has caused a fault in the Viper 20 chip than the transformer. Sugest you look up the data sheet on that chip. Also a picture of the actual circuit board would be of some help when asking people for help. Otherwise its all guess work.
 

dr pepper

Well-Known Member
Most Helpful Member
#14
I suspect the burnt out resistor is the startup resistor, usually a few 100 k to 1 meg or so.
Could be because something else has failed & is preventing the supply from starting up.
 
Thread starter #15
I suspect the burnt out resistor is the startup resistor, usually a few 100 k to 1 meg or so.
Could be because something else has failed & is preventing the supply from starting up.
This may be the case mate thanks .

I have a similar pcb to copy the resistors values from even though not exactly the same layout , but i have a feeling they will boot the system up , had the same issue with a chinese one.
 

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