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corrize · 11-12-2025, 03:12 PM

thank you, 🙂 very unexpected the top bar is a brand
I cleaned it 20 times with a toothbrush and alcohol. The chip is deformed and bulging due to the heat. I couldn't do any better.
I will order it.

corrize · 09-29-2025, 04:18 PM

I have a question please ?
I have not trust on this device’s design (Swiss). I saw 3-4 bad thinks inside.
Now, I have doubt on yellow (tantalum-polymer) capacitors.
Why they are so big ? There is no voltage above 5v inside and the max working voltage is close 3.5v. And it is low power device.
The one soldered with wires (from factory) is 100uF 10v.

Why tantalum-polymer and not ceramic ?
I can’t understand this design choice ?...

corrize · 09-25-2025, 06:11 PM

Thanks for help and the link, it’s this chip. I know where to buy it now if I need.
I will open another thread for diagnose because the chip seems managing charge and end of charge fine. The issue is only the battery logo stuck....

corrize · 09-23-2025, 06:02 PM

That match thanks, I was writing this chip could be probably proprietary chip but you found it. If you have a good database for find components, I want it please ?
So this chip is not power management.
I found another chip (see picture) getting hot (29 degree) when the battery present and charger plugged in. So probably power management chip.
But the same, I can’t find it on the web ?...

corrize · 09-18-2025, 03:43 PM

I learned this device is mostly used on battery mode and in this mode, there is no whistle. So don’t care for this whistle witch is only on plugged mode.
Indeed the whistle probably come from switching power supply. Bad design ; I saw a very long track around the chip when the datasheet recommand very short track to avoid mass loop effect.

I found an audio chip with DAC and analogic amplifier and stuff for speaker on board, but it is good because the whistle is not amplified, it is constant. So the issue come before.

Left 2 issues on one device : false contact somewhere...

corrize · 09-16-2025, 07:53 AM

Good idea, I will try that.
Charger is 6v and the internal battery is 3,7v, so buck.
And there is an USB connector for managing files via a computer.
There is 2 regulators one for battery use, one for charger use and charging mode (chips heating a little under thermal camera) :
LP2992
https://www.ti.com/lit/ds/symlink/lp2992.pdf

and LP3985
https://www.ti.com/lit/ds/symlink/lp3985.pdf
Those chips have output capacitor for frequency filtering, I will try to replace it by news....

corrize · 09-15-2025, 09:24 AM

Yes but we can forget the speaker now, I desoldered it (2 wires) for 2 devices, and the same. Same whistle in the headphones. The whistle frequency change a little when I push on buttons.
These devices are too small and simple to have ground issues, I assume the problem is more likely a frequency filtering component that has changed its value. Because both devices have the same problem and are the same age: 25 years.
I could try to replace yellows tentalum capacitors by black ones (if I have) ? Or better ones ?...

corrize · 09-14-2025, 05:56 PM

Yes I just saw that on picture : lower left under the card socket seems could be a solder bridge with wire, but it’s only flux and dust because I desoldered the card socket (plastic stuck inside).
I need to check one speaker state because it make a bad noise but I have 2 devices, twice make the same Whistle and it is electronic : I heard it in speakers and headphones (I restested, sorry). It is permanent, it is present in audio menus for navigate, when reading mp3 files, etc. This whistle in constant when I turn the volume up and down.
But the whistle frequency variate a little when...

corrize · 09-12-2025, 06:17 AM

To give an overview :
The input plug (220v) is at bottom right.
The brown round stuff beside is the main fuse.
The two rectangular black stuff close are capacitors.
The diodes bridge is under, on the other face : the black square stuff with 4 pins (cms)
Under the black plastic shield, there is another transformer.
The component screwed on heatsink (close orange capacitor) is MX0341B (or MX0341). I don’t know what it is, no datasheet. I found it on Aliexpress as ‘regulator’ ? But with 2x3pins, yes look like a dual transistor package. (It was burned on the...

corrize · 09-11-2025, 04:01 PM

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 ...

corrize · 09-11-2025, 04:31 AM

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...

corrize · 07-03-2025, 03:46 AM

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....

corrize · 07-01-2025, 06:56 PM

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....

corrize · 07-01-2025, 07:22 AM

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,...

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