Dps-240fb

[amadorclub]

Re: Dps-240fb

Friends, The source is burning IC901 (tny268pn) and R910 (10R). Exchanging components source is beeping. What are the probable causes?

Help me, help

[rtstorm]

Re: Dps-240fb

here is the pics, i think the smps has burned, i have been persistent but you cannot fix everything. a least i learn something.

[ben7]

Re: Dps-240fb

i connect everything and fire up, i got flames hahha, it is now total dead. I am giving up. Thank you for help, i learn a lot from you.

I figured that would happen, smps are tricky!

Alright, I was kind of wanting to give up on this one too.

Hey, no pics of it before it gets 'buried'?

What burnt out? Let me guess, the resistors you put in?

[rtstorm]

Re: Dps-240fb

i connect everything and fire up, i got flames hahha, it is now total dead. I am giving up. Thank you for help, i learn a lot from you.

[ben7]

Re: Dps-240fb

I guess the 0.3 ohm will be fine. If anything, it will just trigger over-current sensing at less power than before.

[rtstorm]

Re: Dps-240fb

i will put all together, i will use 0.3ohm 2W resistor for testing, i ordered 3x 0.2ohm but i have to wait week or two. IS that OK?

[rtstorm]

Re: Dps-240fb

the new K3473 FET arrived. I am still searching for 0.2Ohm resistor. I thought connect 2x 0.1 Ohm but there is no space on PCB board.

[ben7]

Re: Dps-240fb

Yes

[rtstorm]

Re: Dps-240fb

In serial connection?

[ben7]

Re: Dps-240fb

Can i connect 2 0.1 ohm resistor to get 0.2ohm?
I am from little town with one electronic shop and they dont have all i need for repair

Yes you can do that.

[rtstorm]

Re: Dps-240fb

Can i connect 2 0.1 ohm resistor to get 0.2ohm?
I am from little town with one electronic shop and they dont have all i need for repair

[rtstorm]

Re: Dps-240fb

Original is 0.2ohm but i dont know W? Is te problem in 0.1ohm or 1W?

[ben7]

Re: Dps-240fb

Can i use 0.1ohm 1W resistor to replace the three burned resistor?

No, I wouldn't recommend it.

[rtstorm]

Re: Dps-240fb

Can i use 0.1ohm 1W resistor to replace the three burned resistor?

[ben7]

Re: Dps-240fb

You sure D2 is ok? Test it by using diode test mode on your multimeter. It should measure something in only one direction. If the reading you get is on both ways, or it is lower than 0.2, then the diode is bad.

Could you try removing and then testing that ceramic capacitor under that coil near D2? See if the capacitor is shorted.

[rtstorm]

Re: Dps-240fb

I think D2 was ok before, i canot remember. I order K3473 FET (Q1) i am not sure that it is ok. Tomorrow i will replace burned resistors and diode. I suspect that Q1 is open all the time. I thinkit is N-channel FET and i am not 100% sure how to test it.

[ben7]

Re: Dps-240fb

D2 diode is broken (run on both sides) BYV 26C PH
D1 is OK.
Q1 - i am not sure, i think it is OK no shorted pins.
D4 is OK
Q2 is OK

i found value of resistor.

Ok, i wont turn it on until we check all.

It's possible that D2 is what was causing the shorting. However, could you get a picture of the bottom side of the PSU in that general area?

[rtstorm]

Re: Dps-240fb

D2 diode is broken (run on both sides) BYV 26C PH
D1 is OK.
Q1 - i am not sure, i think it is OK no shorted pins.
D4 is OK
Q2 is OK

i found value of resistor.

Ok, i wont turn it on until we check all.

[ben7]

Re: Dps-240fb

the main fuse did not burned, so i dont think that the lightbulb would help.

BUT, it takes time for it to burn out. In SMPS circuits, usually the fuse isn't fast enough to prevent big failures. It is still included though to break the current flow when there is a sustained short. Or else things could get hot enough to catch fire, etc...

[rtstorm]

Re: Dps-240fb

Edit2: this is why the lightbulb tester is useful, to prevent catastrophic failures like this one...

the main fuse did not burned, so i dont think that the lightbulb would help.

I will check these component