Hi mates, this router was unfortunately hitted by a water leak, after a couple of weeks when I saw it, it appeared switched off, connected to the power by its PSU which emitted a strange sound (typical switching sounds of attempting to boot on when the load isn't ok, but probably it suffer from condenser ESR reather than a router power problem).
So I opened it, removed the heat sink, cleaned with alcool, then I power it on for a second by another PSU 12v 2A and the LEDS turned on! Suddenly I power it off, put back the thermal paste, assembled the sink and conencted antennas, then turned on and by 4 hours it worked perfectly.
The router is safe and working stable, no errors, no memory faults in Resources.
Then I power it on with its PSU and again it died, that's really strange, it was connected to it by weeks..
the PSU powers out 23,4v, that not so much, it can't damage the router. I waited and power gain by 12V but no signs.
There is something wrong with the power checking after the power connector, there are transistors there, they check if the power is proper, chances are one of them got broken for some reasons, I would try to bypass it and save the router from garbage, as it is working..
Thank you for help!
An important update, today as some days passed from the last attept I've tried to boot it by 12V and worked, I've installed the latest 7.21.1 and also upgraded bootloader, rebooted y software all was ok, again no errors and bla bla.
Then I power it off and again on, it's dead.
Now another attempt and it works.. stable, already 2 hours I'm using it
Something is not good at the power check, what can be?
I've measured the ESR of the 2 big capacitors and it's ok.
I may be something wrong with the startup of the DCDC converter
Are you trying to re-use the power adapter which was connected to device during the water leak? If so, it could be that it's actually power adapter which is half-dead. Power adapter with nominal output voltage of 24V will usually provide that or even slightly more, not less ... and there were many reports where bad power adapters would output almost correct voltage when not loaded but would dip under load (or output very messy voltage ... which can only be seen on an oscilloscope, usual multimeters are not capable of detecting such problem).
Thank for replying, as I wrote I'm using 12V 2A, as the frst time I got it work. I don't understand why after using its bad PSU the router didn't work and didn't work when I back to 12V, i've tried many times, after 1 min, 5 min, 1 hour, 3 hours, 24 hours, didn't work, I thought I would trash it.
Today I've decided to ask here before garbage it, I gave him another power after one week, it worked with 12V, I disconnected and powered again with 12V, dead, I disconnected and powered again and it worked.
I tried to describe deeper my attempts, I hope it's more clear )
The hAP Ac3 has 12-28V power input.
12V is "marginal", try with another 24V adapter, at least 1A, better if 1.5 A.
All in all it sounds like a defective (electrolytic) capacitor issue, even if usually there is lots of allowance for diminishing capacity over time, sometimes they go as low as 1/10 or 1/20 of their original, and this prevents the circuit to work correctly, expecially at power on, where there might be a surge of power needed.
The router workrd for 5 hours, then I disconnect the 12v 2A power supply (good quality, not a commin chinese) and I simply reconnected it, the router was dead.
then I tried with another 24v original Mikrotik, still dead. I've tried connecting different times, no way. In this condition it is necessary to wait about 2 days to work back, which is no sense, the router doesn't have a battery and capacitors cannot sote energy probably more than 10 min.
I've changed the 2 electrlitics but it didn't have effect, I measured them and capacity and ESR are ok.
In my opinion the problem is located on internal DCDC (that doesn't start for some reasons) or on the transistors which allow the power come after testing values and polarity. Tomorrow I'll try to clean the board better, if may the water+dust has created a kind of impedence around the strict pins of micro electronics
Mingling with the stupidly tiny SMD components on a modern board is in itself difficult, and it's strange that the thingy sometimes works.
Usually (not specifically on Mikrotik boards) what fails is - besides the capacitors - some Mosfet, but then the board won't power at all, the "power only once after 1 or 2 days disconnected" symptoms are unusual.
Capacitors in a circuit like that will probably hold charge for seconds, not minutes.
Without a specific manual, identifying the components, even once the faulty one(s) is/are detected may be problematic in itself.
I have seen videos of people "repairing" Mikrotik boards by bypassing the whole power regulating circuitry replacing it with a multi-voltage buck converter "generic" little board, but of course your mileage may vary.
Thank you dear friend, this is what I aim to find, a scheme that clears a bit what is going on..
Yes it is very strange, it is connected with some control, and for some unknow reasons it decides to power on the board, ot to stay mute. The behavious is unpredictable, couple of times I managed to see it working after 2 seconds power reconnection (so temperature is neither a problem here), the rest of the times it stay dead.
I've cleaned the board on power zone with alcool and brush, waited it dries, but it didn't help.
DC/DC converters, also known as DC/DC converters or DC voltage converters, are electronic devices used to change DC voltage from one level to another. In other words, they change one DC voltage (e.g., 5V) to another DC voltage (e.g., 12V) while maintaining a constant current. They are key devices in powering various types of electronics.
How do DC/DC converters work?
The basic principle of DC/DC converters is based on the conversion of electrical energy from one form to another. The general operating diagram of a DC/DC converter includes three main components:
PWM (Pulse Width Modulation) modulator: This component generates pulses of constant frequency but variable width. This allows the converter to control the current and regulate the output voltage.
Converter: The converter consists of an inductor, a capacitor, and a diode. The inductor is a key component that stores electrical energy and converts voltage.
Regulation circuit: This circuit monitors the output voltage and adjusts the PWM pulse width in the modulator to maintain a stable output voltage, regardless of changes in input voltage or load.
During operation, the DC/DC converter accepts a constant voltage from a source (e.g., a battery or power supply) and converts it to the desired output voltage. This allows you to power electronic devices that require a different voltage than that available from the source.
So, there is so many possible points of failures. Do not know if buing the new one wouldn't be cheaper than repairing.
if PWM regultor does not start -> no output voltage
if PWM pulses are to short -> too low output voltage
if capicitors are dried -> PWN malfunction -> no output
if inductor is almost burnt out -> PWM starts or not -> no output
diode's current "leaks" -> PWM malfunction -> no output
regulator is "out of order" -> bad output
voltage comparator in regulator is broken -> no output
Regulator could integrated one or it could be made from these tiny discreete elements. Without schema, it's hard to guess.
