In the first image you can see that 9V comes in but does not get past the yellow components connected to the yellow line.
An XL1410 is supposed to go on the pads inside the red square. The pad where the SW pin goes has continuity with ground. When XL1410 was installed Q12 had continuity with and the VIN of XL1410 received proper voltage but SW did not get any voltage.
The diode below the red square and above D3 has pads that have continuity between them and with ground. When that diode was removed and circuit was powered, the XL1410 overheated.
Both of the inductors have continuity with ground.
The second picture is of the other side of the same PCB in the first picture.
Whatever is marked up indicates where there is a connection to ground.
When the circuit was powered the MCU intermittently overheated. The MCU gets 1V at several pins.
I do not have the schematics for this device.
It appears as though one side of L1 goes to ground and the other side is 3.3V?! That cannot be good.
It’s very difficult to follow the circuit board because J1 is visible on one side, but not the other so it’s hard to figure out which way the board was flipped. Parts of this board are cut off in the image.
More information will be needed to help you with this. Does this board have just 2 layers or are there middle layers as well? How exactly does power get to this board, is there a jack, edge connector, wires soldered to pads? Can you take a photo without the shadows and get the entire board in the image? The diode, D3, may be bad (shorted), have you tested that? What kind of device did this board come out of and what happened before and after the device failed, if you know?
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L1 gets 0V
D3 gets 0.194V one way and OL the other in diode mode
The input jack is marked in the pictures provided
It came out of an Avatar PD705 and I received it in this state - does not power on.
Attached are two pictures of the same PCB showing that the 9V is stopping at a MOSFET where it reaches the gate and source but not the drain. The drain has continuity with one of the pads to the immediate upper right of it, which is where the VIN pin of an XL1410 IC is located. The problem was that the VIN did not send voltage to the SW. But the problem now is that the drain is not getting voltage.
Hello,
Welcome to the DigiKey TechForum. Without the board in hand it will be very difficult to try find the issue with the board and as Gromit mentioned more information will be needed.
Of course, I agree to provide whatever information you require. Please let me know what is missing from the information that I provided. I thought the purpose of this forum was to guide novices like myself in this field.
Hello @solver,
Locating a short circuit on a PCB can be challenging ever for the most experienced technician. The best we can offer are a few guidelines:
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Schematics are essential to understand the circuit. Only the best technicians would attempt the repair with this essential roadmap.
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A “hard” short typically involves a shorted semiconductor. A technician may be forced to remove individual components from the PCB starting with the most likely cause e.g., power semiconductors. This is a delicate process with a real risk of damaging the board.
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Capacitors are also prone to shorting. Given the age of your equipment this would not be my first guess.
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There are exceptions to the rule.
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There is more than just replacing the part. I could be mistaken but it looks like your board is conformal coated which adds an additional dimension to the repair.
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Some people like Northridge make the job look simple. However, he is the 1 on 100 or maybe 1 in 10,000 who can glide through the work.
Sorry I could not offer additional assistance.
Best wishes,
APDahlen