| Electronics > Projects, Designs, and Technical Stuff |
| Need help with SMPS / MA3810 chip |
| << < (4/5) > >> |
| flolic:
I tried everything and only thing that can still be broken is transformer. It looks perfectly normal, no funny smell and no breaks in windings. But I think it must have shorted few turns in primary winding. I connected primary winding to my FG through 50 ohm serial resistor. FG is set to pulse mode, pulse width is 1us with 10V amplitude. Scope is connected directly to winding. What do you think? |
| level13:
did you found the problem with that IC? I have the similar board from daikin have same problem. |
| peter.mitchell:
1) find out what voltage/current requirements are 2) find power rails on board 3) desolder existing components 4) attach external 3rd party isolated power supply 5) close the lid and forgeddaboutit |
| nuno:
Same problem here, also by water damage. PSU doesn't come up. Everything looks ok except an apparently damaged (open) diode inside the PSU IC (VD1 in the attach). I bypassed it with an external diode but it still doesn't "convert". Voltage gets there. Anyone with further information? I found the internal schematics of MA2810 and I assume the MA3810 is similar just different power handling (similar datasheets; datasheets are incomplete, no pinout nor internal diagram :palm:), (reverse enginneered) schematics makes sense with such internals, see MA2810 internal diagram attached. Can't find any manual, schematics, whatever for this A/C model; can find for the newer models but not for these older ones |O Unfortunately this PSU has also several outputs with other voltages and opto couplers and other stuff, I haven't looked into it in detail, which doesn't make the task of replacing it with something "off board" easy. By the way, I have fixed this board before (another totally different problem, track corroded), and it can be powered up by 62VDC into the mains AC input, so it's an easy test. I didn't try lower voltages to see what's the minimum. Plug-in the LEDs board's 2 connectors, as one of them (the big red one) is for a mains fuse which lives in the LEDs board. The board consumes ~30mA with nothing else connected. |
| nuno:
I'll take the opportunity to tell a tale of a pitfall :D I use 2 series ungrounded 31V max lab DC power supplies to get the 62V. In my naiveness, I set and forget one's limit to 1A and then controlled the limit on the other (much lower, 50 - 100mA). In the test (the one with the bypassing diode I mention above), there's almost a short on the input supply. Fact: these lab PSU settings don't provide protection... because the 100mA limited PSU forces zero voltage, but the other PSU's current can still pass through the 0V source, so I provided 31V 1A to the equipment. Gladly I am always on alert and act quiclkly. |
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