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Sometimes it really is that tiny LDO you don’t sespect is faulty, but actually it is. 5
Sometimes it really is that tiny LDO you don’t sespect is faulty, but actually it is.
Sometimes it really is that tiny LDO you don’t sespect is faulty, but actually it is.
I purchased an older Yamaha hdmi 7.2 receiver for use in the basement. Shortly after connecting everything it stopped working and went into fault protection. (red blinking power led)
After some analysis I found a 3.3V LDO was faulty, out=in= 5.6V. Ouch!
It’s job was only to feed the standby LED an a few pieces of glue logic. Though it’s output also fed into the power supply standby circuit.
It’s clever enough to realise that there was an over voltage condition and would refuse to power up. Even when attempting to bypass the protection mode as per the service manual.
Well designed! Except for the LDO it seems.
Replacing it with an 78L33 did the trick.
Stupidest fault I ever encountered was shorted capacitor in laptop cover being closed detection circuit right beside hall sensor. It took me a long time to find this one
Good job fault finding.
I just had a cracked resistor that looked good by eye and by microscope but turned out to be open.
[https://www.youtube.com/shorts/nP8J5gW-l_g](https://www.youtube.com/shorts/nP8J5gW-l_g)
My experience says, DC-DC converters, be they linear or switched, are the first ones to break. And I think it’s a good thing, cuz if overvoltaged, they protect the rest of the circuit.
Not so tiny now, is it!