Replacing resistor fuse in Sony DV charger

[corrize]

Hello, I have 2 old chargers for Sony DV, and I found the same resistor fuse dead. Fuse is a crossing component : 0,47 Ohms (0,125W deduced because the lenght is 3mm). But I can’t find the same for buy.
So, I want to replace by another like 0 Ohms, 1 Ohms 0,125W,
It is the same please ? I guess it’s the same, the only change should be the time to burn ? Thanks

[CapLeaker]

Not sure what the problem is, but you should be looking why that resistor blew up first place? The could be more than just the blown resistor.
Now as for the replacement resistor. I just looked at Digikey and they had like 46000 of these resistors in stock. Just watch the size. It may be that a newer component is a bit smaller than an old one from decades ago. If there is like 1mm in length difference (short), that shouldn’t be a problem. Gives you half of a millimetre on each pad. Maybe upload some straight shot pictures of the board.

[corrize]

I will see for the smaller one…

I found one regulator dead on one board, and nothing to other. I want at least repair one.
I found this resistor on Amazon at 30 euro, it’s probably more with Digikey (I never order ; too expensive). So, I search a workaround.
If this resistor really needs to be replaced with the exact same one, I might as a last resort look at a SMD resistor,

[corrize]

Maybe found ?

https://fr.aliexpress.com/item/1005005633571473.html

The ad is not clear, but in the details, there is : « 1/8W », so matching.
I will ask to seller to be sure.

I found first a SMD resistor ; 0805 is 1/8W, but I prefer crossing resistor in this case ; for a old AC-V700.

[CapLeaker]

Just a through hole resistor… these should be plenty to be found, or just put a SMD part across the pads. It’s nothing much, just a fusible resistor.

[Agent24]

I'm not so sure it's a fusibile resistor? It looks just like a 1% tolerance, 1/8 Watt resistor to me. The 1% ones are often a green or blue colour.
The brown one to the left of it in the photo is a 5% resistor the same wattage.

Also it looks like other things around it are more burnt than it is.
For example, that blue item to the left of it, looks like a capacitor but a strange shape...

Can you provide more photos, of the whole board from both sides, the area of the resistor from different angles, etc.

Also, clean the burnt area with isopropyl alcohol so we can see what is damage or not. A lot of the blackening can just be soot from elsewhere.

[corrize]

I guess it’s a resistor fuse : 0.47 Ohms, 5%, 1/8W
On the 2 boards, I found a big capacitor soldered upside down, and fuse dead, and big regulator dead, and 2 burned resistor fuses. So I will replace all the deads components first, and compare the 2 board. I will see if there is some differences and I let you updated.

[Agent24]

Ah yes, now I can see the colours more clearly I think you are right about it being fusible or flameproof. The tolerance band looked different when it was covered in soot.

I don't think the ones from your AliExpress listing are fusible, they are not the right colour, I think they are just standard.
You could try maybe these https://www.aliexpress.com/item/1005005406100264.html which are 1/4 watt but can probably be put in vertically to fit.
Only has 0.5 Ohm but at 5% with the original part, that would be acceptable

I find the blue capacitor (or MOV?) in the 3rd photo looks strange, it appears to have a lumpy surface, I wonder if it is damaged?

The board also seems to have had some minor corrosion damage too, in places. I wonder if this is related to the fault.

Definitely check all the primary-side components for shorts at least too

[corrize]

Hello, I received the resistors fuses and it is simple resistors (not fuses) and with bigger watt. So not good, but I tryed to power on very quickly under thermal camera for check if something became hot. And…
The big tentalum capacitor (orange) in center of the board instantly blow up. I saw nothing hot under camera (and it is a high refresh one : 50 fps). So I guess this capacitor coud be the guilty ? All other components look good (with meter). I replaced it, and now I want to test to power on.
But I’m not shure, I never saw tentalum capacitor blow up and I don’t know if it is a common root cause of issue or a consequence ? I know chemicals capacitors are often root cause but tentalum, I have no idea ?

[Agent24]

Tantalum often do short, I think from old age and running too close to their voltage rating, but that capacitor in your photo does not look like a tantalum that I know of.

It appears to be a metallised polyester film capacitor of some kind.

Those rarely short and usually fail from overvoltage if so.

[lotas]

Yes, this is not tantalum, but a high-voltage metal film capacitor at 3900pF (3.9nF).

[corrize]

Yes I measured 4nF (I have another same charger, with another issue).
I don’t know what to do for next step to diagnose ? I measured all components at the high voltage part, and found no issue. But I don’t have ESR meter for check capacitors. I replaced the chemicals capacitors by news ones, I replaced fuses. Next step could be a test with voltage ?
I localized the diodes bridge, I could desolder the output for protect the secondary circuit, and mesure this output of diodes bridge for check if I have stable and continuous voltage or not ? (Edit : probably not the output of diodes bridge, more likely the output with continuous voltage ; I dont know where exactly?)
And I soldered another orange capacitor (took of another same charger, so not a new capacitor). But I could remove this orange capacitor only for test, to see if something burn or not ?
What do you think to this step for diagnose please ? Do you see another way ?

[Agent24]

I'm trying to figure out the PSU topology...
I can't easily tell where the blown capacitor or the burnt resistor are in the circuit, so hard to say why they failed.

What is the device on the heatsink next to the blown capacitor? It appears to be some kind of dual-transistor package?