Replacing a burnt out "UN8HX" chip on the DIMIKA dash cam

mister_rf

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YI /GT300W / C1 / DIMIKA / E720 / MOBIUS / DVR207 / 808 # 18
I’ve had the DIMIKA for about a month now, just the other days I noticed that the red light comes on indicating the camera is in charging mode as per the manual, however no charging anymore. Apparently the camera It was working just fine connected to a USB cable.

I have carry out a hard reset of the camera by pressing and holding the RESET button. No success. I removed the battery, in order to do a reset. Same problems, the battery indicator never comes off. Did some checking around and measure the battery, it was not half-charged like it said it was supposed to be by keeping on charging a long period of time.

Before I had to start repairing this piece of electronic equipment, I first had to identify and compare components through web-research, in order to draw a minimal diagram of it. The following schematic diagram shows a circuit to generate the necessary LiPo battery charging.

MCP73831-sch2.png




Based on that it was easy for me to find the faulty components on its printed circuit board. Sometimes, you can identify some bad components on a PCB just by looking at it. So I compared the previous circuit PCB photos I have taken with the actual ones, and I have discovered a small dark area on the surface of one of the ICs. The burn marks were due to overheating of the ICs.

def2.jpg

Circuit marking UN8HX.

This handy little IC will correctly and safely charge the Lithium Polymer batteries with power from a USB port or from a DC wall adapter. Max current is limited to 500mA . Requires almost no external components and will automatically select between internal DC source and the USB source if both are present.


cidef.jpg
 
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mister_rf

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YI /GT300W / C1 / DIMIKA / E720 / MOBIUS / DVR207 / 808 # 18
Research on the web turned up a reference to this IC, by using the popular MCP73831 and no circuit redesign would be needed to.

dimika LIPOL.jpg

First I removed the burnt out chip and cleaned the traces as best I could with a soldering iron and a dedicated electronics toothbrush. The copper traces where near to a disaster, but a salvageable one. I repositioned one of the traces by adding a small copper wire.

def.jpg
A new chip was carefully positioned on top of the pads, and a quick touch with the iron soldered its leads down to what was left of the footprint, all except for one later connected by the blank wire.



IC.jpg


ok12.jpg
 
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mister_rf

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YI /GT300W / C1 / DIMIKA / E720 / MOBIUS / DVR207 / 808 # 18
And sometimes you may get lucky. I set a meter up to test the voltage and plugged the USB cable back into the camera. The charge LED turned on.

Thermal image of the working circuit.

MCP73831.jpg

I left the battery plugged in this time, and about an hour later the light turned off. The battery was fully charged, it seems the fix has worked!
 

kamkar1

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Nice :)
Fjew ppl would be brave enuff to do the same, most just trow avay and buy new.
But i guess the culture is different in Romania, now the rest of us just need to learn from your example.
 

Tobi@s

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How did you fix this one?
 
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mister_rf

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YI /GT300W / C1 / DIMIKA / E720 / MOBIUS / DVR207 / 808 # 18
I have replaced the original PCB circuit trace by using a small piece of copper wire.
The wire must be isolated from the PCB of course.
So I have applied a small piece of office tape on the PCB and glued with a tiny amount of epoxy.

wa.jpg



w2a.jpg
 

Tobi@s

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Thanks!
Have to do something like this with my dead 0801, too :D
 

Tobi@s

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I have a working 0801 but it's in my car and I'm trying to not **** it up like my previous 0801 which I used for testing A2Romkitchen/A7Tool, UART connection, etc :D
But I damaged a few soldering pads by being rude (^^) to my uart connector
 
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mister_rf

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YI /GT300W / C1 / DIMIKA / E720 / MOBIUS / DVR207 / 808 # 18
Nice :)
Fjew ppl would be brave enuff to do the same, most just trow avay and buy new.
But i guess the culture is different in Romania, now the rest of us just need to learn from your example.
Yes, maybe that’s true, but please consider also electronics is one of my hobbies for quite a very, very long time now. :)

By the way, a short IC replacement list for UN8HX:
2YL6, 2YL4, H1JC, 54B4, S9V, HIJH , 55B7, 016Q and LTC4054
 

lpto

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Tuning in with a charge-dead SJ1000 -cam.. I was making a very low profile usb-cable and must have messed up the data and power pins as now thinks it's always charging where in reality it isn't.. Also the camera doesn't seem to work as a webcam anymore either :(.. This was a feature I kind of needed with the low-profile microusb cable.

Camera works fine otherwise, and powers up from microusb, just doesn't charge or isn't recognized properly by the computer (unknown device according to Windows). Using an external charger still allows the camera to be used when just recording. However what also ends up happening is that the battery will be run down to very low voltages, like ~3V, and will only shut down when there just isn't enough voltage, e.g it seems no undervoltage protection is active also. There doesn't appear to be any heat damage to the UN8HX -chip. The label is clearly readable and there is no discoloration.

Questions:

Would a dead UN8HX / USB-charge circuit also disable the computer webcam/card-reader functions?
Could someone confirm, with possibly a broken camera, if disabling the UN8HX or usb-charge circuit also disable the computer functions?
What are the differences between the alternative ICs? Does some of them support higher charging current or something?
 
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