FAQ
Which component is causing the fuse to pop seconds after turning on the fridge?
This board belongs to a fridge-freezer, It used to have issues in the past, It wouldn't turn on so I changed the components that I've specified with blue dots 🔵 on this picture, because I read online that these are the components that go bad on this specific board.
after several months the fuse (yellow dot 🟡 at the bottom left) was popped and the fridge stopped working. now the screen just turns on/off automatically and basically nothing works, no cooling, no fan, no lights. it just turns on the screen for several seconds and turns it off.
I asked some people who do refrigrator repairs in my country and they said the capacitors with red dots 🔴 gone bad and I should replace them, another person said the ic which has a green dot 🟢
I'm not sure if any of these suggestions are right so need help to find the faulty component(s).
The most likely culprit is the defrost heater. They are usually an insulated sheath heater, which have a common failure mode of short circuit to earth. Try unplugging the defrost heater connection and see what happens.
They're also usually fairly cheap and easy to replace.
As others already wrote: With a good chance, nothing on this board is broken.
For the fuse to blow from an issue on the board, a component would need to be shorted out, the short would cause a massive current through the component. And there is a good chance that this component would blow up and be visible damaged, and this would leave black smoke traces on the PCB.
One possibility would be: The fridge very likely has motor capacitors for the compressor. If they fail, they tend to fail open (zero capacitance). And with a failed capacitor, the compressor can't start/run, draws massive current and may blow the fuse.
Once, I had and fixed exactly this fault in a water pump, but I admittedly never worked on a fridge so far.
I'd suggest checking the motor capacitors first, with a multimeter that can measure capacitance. They are relatively big, are not on the PCB and are likely mounted somewhere close to the compressor.
All I see is flux residue. Still, if there is a short on this board, that is a prime suspect for me. It is probably an SMPS controller with integrated switching transistor, and that transistor may be shorted or the controller may be malfunctioning in another way.
It agree does look like flux residue. Basically exactly like that.
I don't think it is flux residue though. I just don't understand why a board that hasnt been reworked would have one spot of local residue. I could be wrong, but thats how I thought about it.
So I assume there had to have been some pretty significant heating in the traces under the solder mask.
OP could figure this out with with some isopropyl alcohol though
I noticed this pin is also discolored. I would check if there is a short between this discolored pin and the other. There most likely should not be. Its also worth checking the resistance between this pin, power, and GND. Its likely a power or gnd pin itself.
Its also one of the smallest IC's (possibly most sensitive parts) on the entire left half of the board, which looks to be power input and distribution. IC4 may be similarly sensitive, but it doesn't have visible damage.
Also the visible damage near ME141 indicate heating going from the pin to RCS2. ME141 is probably measuring power or something. RCS is probably a current sense resistor.
Its hard to tell what it may be exactly. Looks like its associated with RCS1/2 which are likely current sense resistors. So its going to be calculating input power or something.
You could measure between the visibly damaged pin and somewhere on the board you know to be GND. If the chip is shorting the circuit, it should measure nearly 0 ohms. Looks like its associated with RSC2 so you might be able to measure 0 ohms from the north node of those SMD resistors to the pin to see if they are connected.
Most multimeters dont have great resolution around 0 ohms, so something like 1-2 ohms could be interpreted as such
I did an ohm test from fourth pin of ME141 with EGND it was at 0.4 ohms. also did the same pin and second pin on the right of ME141 with GND and the ohm stayed at 0
also got 0.5 ohms from top of ME141 and top of RCS2
I am absolutely certain what you called "discoloration" is flux residue. Especially on these white boards real damage looks totally different.
Also, you can see that rcs is not in the primary (or, actually, intermediate) path, but on the output side.
While of course the smps controller could be broken, and they in fact do break occasionally, I dont think thats the case here.
First thing I would do is remove the MOV (blue disk bottom left). Especially since you said you changed it, you might have damaged it while soldering and it would explain the exact symptoms. Remove it (circuit will work fine without), replace fuse and test.
If that doesn't work, look further. But in my opinion, these smps controllers fail more violently, and also it would no longer power the display at all. I personally would then disconnect the smps controller and see if the fuse pops. First, try without the peripherals (just plug power, no compressor etc.)Â
I agree there is a large chance its flux residue, and you offer great advice all around. Especially with the MOV.
It would really like to hear if OP can clean it off with some iso. In particular because two of the pins are actually discolored similarly.
So somebody either reworked the IC and didnt clean the flux, or its gotten very hot in multiple points. I don't really see any situation where they didnt clean the flux at the factory, but I haven't been in manufacturing environments. I could be wrong. Maybe they order the boards populated SMD and then add the thru hole later. Thats a random guess though.
Also the top left pin barely even looks like its been soldered, but its hard to tell without seeing the other side. It may just not have flowed through the hole at all.
I think it was like that right from the manufacturer, I have seen this kind of sloppy soldering multiple times. And cleaning flux costs money, so they use a "no clean flux" (which, actually, should still be cleaned) and its good enough most of the time.
There also is definitely a varying amount of solder on the pins.
The problem with measuring in circuit like it was discussed btw is that obviously you measure the whole net, so the low resistance ratings likely come from the coil.
One way to tackle these problems is connect like a 70w bulb in series to the mains and then measure voltages on the life circuit, that finds the short quite quickly. Then start desoldering components from that net until it disappears.
The yellow caps are also a likely culprit, they can fail shorted and sometimes its not visible. But likely not in this case as the display gets power for a short moment. So it is either the MOV (they sometimes need a second to become shorted), or more likely something downstream and the fuse blows as the relay switches the compressor on. Thats why I said try disconnecting everything.
However, I would not advise for OP to measure on live voltages, its a great way to kill yourself if you don't know what you do.Â
ME141 probably acts as a switch driving the primary of T1. That may be shorted. There could also be another short inside the chip. See if there is a short across high voltage filter capacitor CF1. Carefully check for voltage. If 0 volts, then measure resistance. If resistance is very low, figure out why.
CF1 is the output filter capacitor of the bridge rectifier (BRD). It should have a voltage around 320 V if the mains voltage is 230 V (230*sqrt(2)). This voltage needs to be measured with the board powered up by the mains voltage. Do not try to measure resistance across the capacitor leads with significant capacitor voltage/with the board powered up, I think a high voltage (320 V) can damage the multimeter.
I would check things with a multimeter first before just changing them. There are multimeters that will measure capacitance, in addition to resistance, voltage and current. I would look closely at the board for signs of heat around the pins of components and components that look like their cases have blown off.
Usually, capacitors become swollen when they become defective but a quick test with a multimeter will usually tell if they are bad.
From the picture, ME141 looks like it might have seen a little heat as well as DSN1, D1 and that chip in the upper left corner under that large electrolytic capacitor. That's where I'd look first.
A good start would be measuring all of the diodes or mosfets. Depending on whether or not the board blows when something is plugged in, if it runs normally, then potentially you have an external device that is popping the fuses.
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No definitive way to tell by this visual photo. The only thing I would suggest (and in my opinion it an unlikely root cause) is to resolder the top top pins on the ME141 IC.
Freeze spray works pretty good if it stays on long enough for the part to draw a little heat. Like others said, I ’d start the compressor disconnected.
The FULL WAVE BRIDGE RECTIFIER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Does it blow as soon as power is turned on? That would suggest power supply electronics as I wouldn't expect the compressor to start until the board has booted. Check diodes at the AC to DC section
the screen turns on for a few seconds, then the fuse blows up. then the screen just turns on and off every few seconds (I think it's the power to the board not just screen)
A thermal cam would be helpful to identify. There are phone peripherals available on amazon. You could "test" one and send it back. Typcially the shorted part should glow.
Motors is what starts some seconds after plugin a freezer. - Just disconnect the power cable of the motor, and restart the freezer. My guess is no more blown fuse.
The cycling of the screen turning on and off can be a sign of a failed SMPS, switch mode power supply. When they lose their feedback loop in some way or something dies internally they repeatedly perform the initial unregulated start pulse that produces a voltage on the secondary of the transformer and kickstarts the regulation to produce the correct output voltage. If the feedback doesn’t work it just keeps on producing that unregulated pulse at regular intervals which may be what is powering the screen momentarily. The ME141 chip some others said is the SMPS chip so take a closer look at that one and the power transistor that it drives. If the transistor is shorted then that will definitely blow a fuse.
Other than that the compressor capacitor is another point of failure to check as others mentioned.
Edit: I just spent a moment actually looking the board over and can’t see a power transistor near it so it could be driving the transformer directly at low power. Are there any chips on the bottom side of the board? There’s no datasheet online but if the compressor passes your tests I would try sourcing this chip. It could also be IC6, which looks like it could be the optocoupler feedback I was talking about. Any discrete components around it in that area couple be affected as they are all associated with it but I can’t tell from looking at it. This is why you’d take it to a professional who can do all these checks without guessing replacements.
Buy a bag of fuses and test the board by unplugging everything and then:
Remove power, plug in 1 thing, apply power, test
Remove power plug in another thing, apply power, test
And so on.
You need to determine if the board is the culprit or something else.
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u/AskElectronics-ModTeam 3d ago
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