Problem with power inverter emc18aecn1 of washing machine AEG L6FBA674

[stomanata]

Hi,
on my previous post with help from this forum i found short circuit GIF5CH60TS-X
I replace it but again give me error for current over 16A.
I measure again and found short circuit between #15 and #16 (Cin and GND).
On PCB i remove R121 to check in which direction is short circuit. But this pin goed
to big copper piece on back side.
So i try to measure over every resistor and capacitor
But i can`t find any short circuit,
On example circuit of GIF5CH60TS-X is labaled that Cin can goes to GND in some cases:
1. Through CSF (i don`t know where is he)
2. Through RSF and Rshunt
3. Through RSF and MCU/op-amp
4. Through RSF and Rshunt and then C4 or Cvdc
Any help?

[CapLeaker]

Maybe there is something wrong with the motor?

[stomanata]

Maybe there is something wrong with the motor?

no, no.
I have short circuit with everything disconected - only this PCB from attach and still
there is short circuit

[CapLeaker]

no, no.
I have short circuit with everything disconected - only this PCB from attach and still
there is short circuit

I remember this case now… this was a no spin, right? You may have gotten a bad motor drive controller IC, or there is something else broken. Measure the resistance between CIN pin 15 and the low side output pins 18, 19 and 20.

[stomanata]

I remember this case now… this was a no spin, right? You may have gotten a bad motor drive controller IC, or there is something else broken. Measure the resistance between CIN pin 15 and the low side output pins 18, 19 and 20.

Yes, case with no spin.
I replace GIF5CH60TS-X, but after again error i start to measure again and notice short circuit
between Cin (pin #15) and GND (pin #16).
This i why i desolder 1 resistor and notice that short circuit come from other line, but
it is big Cu plate on PCB and is connected to too much elements. So i try to measure
all resistors and capacitors but no luck...

[CapLeaker]

So you are getting that E57 (over current) error? Since nothing is shorted, all I can think of is maybe a through hole is bad, or a resistor changed value and it went high in resistance / open and thus is out of spec.

[stomanata]

Biggest question is how to find defective component?
Stupid solution is to desolder component by component until
short is gone

[CapLeaker]

All depends on your capabilities. Your way is the long, complicated way. For shorts you need a meter that can reads resistance below you regular DMM. There are things like a Leakseaker 89 too. Thats how I figure out complicated shorts. But not everyone has such a thing. Like I said, it could be a short, but the problem could be also a resistor went open or higher that it should be. There is also a thermal camera to spot something hot, when feeding power to the shorted line. Another way to find a short is using 99% rubbing alcohol, douse some components and feed the shorted line power with the CV / CC bench power supply and see what gets hot. The alcohol will vapour off quickly. Most times I use the alcohol method, even so I got all 3 options to my disposal. This being said, if going gets tough, my Leakseaker 89 finds it every time.

What did you come up with the resistance measuments suggested in my post #4?

[stomanata]

Yes, removing components will waste a lot of time.
Why i need device that can reads resistance below my regular DMM?
I have short circuit between 2 pins.
I measure with my DMM in "diode" condition every resistor, capacitor and 3 transistors.
But i can`t find component that has low resistance. There is 6-7 resistors with low
resistance but they are OK.
I think that thermal camera or alcohol method will be not usable, because
electronics try to start but i read error and stop.

[CapLeaker]

Yes, removing components will waste a lot of time.
Why i need device that can reads resistance below my regular DMM?
I have short circuit between 2 pins.

Because it gives you more resolution and you can tell if you are going the right way looking for the short.
For example: if your resolution is 0.01 Ohm, it's a short. But you find it everywhere on that trace, because there is no lower resolution. Now if you can measure in milliohm or microohm, resistances will be different. in that scale. On the same trace further away it will be a higher microohm reading than there where the short actually is. Resolution is king and fault finding technique is king.

If you inject voltage on that shorted trace only the bad component gets hot, unless it is Vcc for certain chips. That means you have to remove the IC or cut a trace.
A good head scratching example of a short using the alcohol and voltage inject method in a power supply I did is here: https://www.badcaps.net/forum/troubl...-output-repair
There is also a Feeltech/Kuman repair where I used this technique. I am not powering the whole thing. I only force fed power to the shorted trace. Just be careful and stay withing the voltage range in that trace.

[stomanata]

Thank you. Now i understand. I didn`t know that we talk for even microohm resolution
So what current to try to apply between pin #15 and GND?
May be 0.5A to don`t burn some copper track - 5VDC with 10 ohm/2W resistor?

[CapLeaker]

You need a constant voltage / constant current bench power supply. Not just some regular power supply. Before you use this method, try it on a junk board so you get a feel for it. On how much voltage and current to use. I'd start with 3 volt and just rack up the current from 0.5A to to be safer. For one volt I used 5A before. If you use more voltage than the circuit is designed for, you have to take voltage sensitive components out. Sometimes it takes a few minutes for it to get hot. All depends on the component and the heat sink.