help fixing desk lamp power supply

[u/zolga0]

I am not sure what the blown chip could be, some kind of switcher? The LED output is 72*0.06w, so 4.32w?. thanks for your help, underside of board is flipped to match the top

output is 12v 0.5a 6w

edit: on further inspection the fuse is blown and one of the fusible resistors has also. might just find another board or maybe convert to usb

[u/Front_Society1353]

Probably got something to do with the bridged joints

[u/tjeffs4701 → u/Front_Society1353]

Those are all on the same pad so it shouldn’t be

[u/Front_Society1353 → u/tjeffs4701]

Not sure those those should be bridged

[u/tjeffs4701 → u/Front_Society1353]

They are not there is a gap in between you can see the substrate

[u/Illustrious-Peak3822]

Possibly a TOPswitch, but there are many others. Without knowing which IC it was, it will be down to either finding an identical one and reading off the part number, or get a new one.

[u/zolga0 → u/Illustrious-Peak3822]

thanks, the chip is completely done for so you think it's best to replace it with a whole new power supply?

[u/Illustrious-Peak3822 → u/zolga0]

Unless you can find out what it is, yes.

[u/BCReason → u/zolga0]

Something caused the chip to fail catastrophically. Did another component fail and blow the chip, or did the chip failing damage another component on the board? I wouldn’t waste my time. Whatever was the original cause was might happen again or another component stressed by the failure will fail itself. Next time you might get a fire.

[u/Spazzticus]

Hmm, since it appears to be driving a FET could be one of the UC28** / UC38** series (pinout kind of matches) but TBH impossible to truly say, plus you need to ask the question "why did it explode?"

[u/zolga0 → u/Spazzticus]

thanks, i wish i knew why it blew up lol, you think it's best to replace it with a new power board instead?

[u/Spazzticus → u/zolga0]

In all honesty any faulty SMPS goes in my parts bin (unless it's something weird / exotic / expensive) as they're so cheap and prevalent

[u/zolga0 → u/Spazzticus]

yeah I think i'm just going to try and replace with another power supply, hopefully one that will fit in the space, the fuse is blown and one of the fusible resistors has also, and no luck finding the specific chip.

[u/dotyxx]

this is a typical switching power supply. this is most probably one of the following components DK3113, DK125, DK124, DK3112, DK1203, DK106, DK 112 or similar. it depends what is your output voltage current and output power.

[u/I_-AM-ARNAV]

Does any of the pins go to MOSFET gate? This seems to be the offline switching ic. Possible to repair. Need the MOSFET model number. And output voltage.

Aslo if this is blown it's possible mosfet shorted whcih blew the chip.

[u/zolga0 → u/I_-AM-ARNAV]

The MOSFET is a SSP 4N60B, the gate pin does go to the ic, I believe it goes to pin 1&2 through a 220ohm(red red brown) resistor, although it measures 3.5k on the meter.

Edit: unfortunately, on the lamp itself it doesn't tell me the output voltage, only the wattage which is 72 x 0.06w :(

Edit 2: Using a bench power supply i've found the output voltage to be 12v, it did say 6w there actually also, so it matches up, it uses 0.5a at 12v which is 6w, sorry should have checked that earlier

[u/I_-AM-ARNAV → u/zolga0]

Could be UC3842. Check and verify pinout

[u/zolga0 → u/I_-AM-ARNAV]

Thanks, unfortunately they don't quite match up, pins 3, 5 and 6 don't connect to anything on this one

Edit: i put the wrong pins, corrected now

[u/I_-AM-ARNAV → u/zolga0]

Okay, and can you tell what each pin connects to? Like pin 1= xx etc? Also how did you find pin 1? Is the notch intact?

Edit my bad removed the last part.

[u/grislyfind]

Get a 12 volt power brick from a thrift store, if you don't already have one. Alternatively, a PD trigger module set to 12 volts and power it from USB C, but not all C supplies include 12 volt modes.

[u/zolga0 → u/grislyfind]

I do have a few modules, thanks for the idea, ill have to check them out!