Hi,
I am checking a charger that used a 14-tap transformer， the measurement as follow:
R8-10 = 0.6 Ω;
R12-14 = 0.4 Ω;
R4-7 = 0.3 Ω;
R3-7 = 0.3 Ω;
R3-4 = 0.3 Ω;
All other pins are empty, no soldering actually except pin13 which soldered but no connect to any other pins on transformer, that did connected to other component.

A schematic picture not a real transformer attached.
Thanks
Adam

 

Resistance measurements do not reveal anything about the transformer except the DC resistance of the winding.
You need to apply AC voltage at the specified frequency to the primary winding and measure the AC voltage at the secondary winding.

 

What's the core made of?

 

I would suspect that the last 3 readings you show are the resistance of your test leads. It is probably a fairly high frequency transformer with a ferite core and very few turns.

 

How about a picture or two?

 

Resistance measurements do not reveal anything about the transformer except the DC resistance of the winding.
You need to apply AC voltage at the specified frequency to the primary winding and measure the AC voltage at the secondary winding.

Thanks,
I'll try it. I didn't do that way because of the first input signal is from the + output of a Rectifier bridge and through a UC3842 module generate PWM to excite the transformation (not very sure yet). and I don't know what voltage should use to do the test.

 

What's the core made of?

Thanks.
the transformer is wrapped up can't.

 

If you'd mentioned UC3842 earlier, we would have known immediately that it was a flyback transformer.
I'm assuming that the charger runs off the mains.
You'll find one terminal of the transformer connected to the drain terminal of a MOSFET. I bet that MOSFET has failed.

 

How about a picture or two?

Thanks.
Pictures attached.
BTW. any one known a circuit like this one that used: ru7088r/ mbr20100ct/FS10KM/UC3842.

 

If you'd mentioned UC3842 earlier, we would have known immediately that it was a flyback transformer.
I'm assuming that the charger runs off the mains.
You'll find one terminal of the transformer connected to the drain terminal of a MOSFET. I bet that MOSFET has failed.

Thanks.
You are right.
The charger used: ru7088r/ mbr20100ct/FS10KM/UC3842.
It looks on the bright side， there are few resistances burnt, the true reason maybe like you said.


The terminal 10 of the transformer connected to the drain terminal of a MOSFET FS10KM, that is controlled by UC3842 module through gate.

 

Looks like they got their dog to solder it.
With that many components soldered on the back, I'm not surprised it failed. Obviously it didn't work as they designed it, then they added various bits to see if they could fix it.

 

Looks like they got their dog to solder it.
With that many components soldered on the back, I'm not surprised it failed. Obviously it didn't work as they designed it, then they added various bits to see if they could fix it.

Thanks.
Seems it is.
I draw a diagram of it, need help please:
1. any thing wrong with the drawing?
2. any improvement can make?
3. how the J6 on/off control the 12v/24v output?

 

Ok,
Attached the drawing again for a easy look. and still need help on how to modify it to avoid burn again.
Thanks