LG 32LN575S No power Blown fuse.

[Dragunov]

Hello guys I have here a 32LN575S that died while it was in standby for a while... Opened it up and found that primary fuse was blown...
I desoldered the fuse and soldered a copper wire over it (dont know how to say it in english but one wire thiny). Didnt pulg it in yet dont know if the wire is to thick.

Can you please help me check what might cause this and how to test/repair it.

I have a standard multimeter and i also found a service manual for LN57xx series.
Pictures and a manual in attachment.

Many thanks guys

[R_J]

Re: LG 32LN575S No power Blown fuse.

Don't do it, You have a blown resistor, R113, so I suspect a shorted transistor Q101 and maybe damaged ic101. I would also replace C103 (100µf/50v) capacitor

[Dragunov]

Re: LG 32LN575S No power Blown fuse.

Don't do it, You have a blown resistor, R113, so I suspect a shorted transistor Q101 and maybe damaged ic101. I would also replace C103 (100µf/50v) capacitor

Q101 is MDF11N65B N-channel MOSFET when i connect source with a Gate in diode mode i get short (beep) as i can find on the internet it is faulty.

R113 I have no reading in diode mode so its faulty.

I cant find IC101 where is it? (did you mean IC102?)

[jetadm123]

Re: LG 32LN575S No power Blown fuse.

You should use resistance mode to read R113. Not diode mode.

IC101 should under the board (green side).

[Dragunov]

Re: LG 32LN575S No power Blown fuse.

You should use resistance mode to read R113. Not diode mode.

IC101 should under the board (green side).

R113 it doesnt matter it has a burned hole in its side (It should be Resistor: 0.25 Ohms 5%)

IC101 Please check picture...

I will try to find replacement MOSFET in junk at home can you please tell me what values i need to find so i can replace it...

Thx

[R_J]

Re: LG 32LN575S No power Blown fuse.

The ic drives the fet gate. If the Drain shorts to Gate, it will supply full Dc (160~300vdc) to the ic. Check the resistors and diode on the gate, R107, R106, D103 and also R106 (when R113 opens it can supply full dc to r106 and open R106 and also damage the ic)
The ic should be SC1S311A, It might be ok, but if it is not it will blow the fet again.
R113 should be 0.15Ω

[Dragunov]

Re: LG 32LN575S No power Blown fuse.

The ic drives the fet gate. If the Drain shorts to Gate, it will supply full Dc (160~300vdc) to the ic. Check the resistors and diode on the gate, R107, R106, D103 and also R106 (when R113 opens it can supply full dc to r106 and open R106 and also damage the ic)
The ic should be SC1S311A, It might be ok, but if it is not it will blow the fet again.
R113 should be 0.15Ω

Uffff ok let me check the junk first and find a compatible replacement for that fat and then we will go from there...

[Dragunov]

Re: LG 32LN575S No power Blown fuse.

The ic drives the fet gate. If the Drain shorts to Gate, it will supply full Dc (160~300vdc) to the ic. Check the resistors and diode on the gate, R107, R106, D103 and also R106 (when R113 opens it can supply full dc to r106 and open R106 and also damage the ic)
The ic should be SC1S311A, It might be ok, but if it is not it will blow the fet again.
R113 should be 0.15Ω

I need to order a new transistor...

I will order...
2x MDF11N65B (one spare if it burns out)
2x resistor red, green, silver, gold (check picture it should be 0.25 by calc)

I did not check IC, R107, R106(dont know how to check them properly) if it burns out i will order them later... D103 is ok.

What about that fuse is that wire ok?

[R_J]

Re: LG 32LN575S No power Blown fuse.

If you are ordering parts why not get a few fuses? I can see the resistor colors better in this picture so 0.25Ω it is. You can check the other resistors in circuit, R106 connects R113 to the current sense pin of the ic, if R106 is open the ic will not detect any current flowing through the fet and may not operate. If R107,R108 are open or if D103 is shorted you may not have any gate drive for the fet.

[Dragunov]

Re: LG 32LN575S No power Blown fuse.

If you are ordering parts why not get a few fuses? I can see the resistor colors better in this picture so 0.25Ω it is. You can check the other resistors in circuit, R106 connects R113 to the current sense pin of the ic, if R106 is open the ic will not detect any current flowing through the fet and may not operate. If R107,R108 are open or if D103 is shorted you may not have any gate drive for the fet.

Ok so on what do i need to set my multimeter and what readings should i get from R106, R107, R108 in circuit?

[R_J]

Re: LG 32LN575S No power Blown fuse.

I can't make out the markings on the resistors on your board but I believe they are:
R106 220Ω use the 2K scale
R107 22Ω use the 200 scale
R108 100Ω use the 200 scale
D103 should check using "diode test" but may not check properly because of R106 & R107 so just make sure it is not shorted.

[Dragunov]

Re: LG 32LN575S No power Blown fuse.

I can't make out the markings on the resistors on your board but I believe they are:
R106 220Ω use the 2K scale
R107 22Ω use the 200 scale
R108 100Ω use the 200 scale
D103 should check using "diode test" but may not check properly because of R106 & R107 so just make sure it is not shorted.

Hmmmm im posting higher res picture of the area... now you can see values on them.

R106 No reading (because it is in circuit?)
R107 No reading (because it is in circuit?)
R108 says 100
D103 says 637 one way and the other no reading

[yokoono]

Re: LG 32LN575S No power Blown fuse.

220 = 22 ohms
101 = 100 ohms
221 = 220 ohms

[R_J]

Re: LG 32LN575S No power Blown fuse.

I am sure you should get a reading on the resistors, even in circuit, The reading on the diode, is correct but I would expect a different reading if the resistors were good so I would look closely at the resistors, I suspect they are open.
This should help you:

[Dragunov]

Re: LG 32LN575S No power Blown fuse.

I am sure you should get a reading on the resistors, even in circuit, The reading on the diode, is correct but I would expect a different reading if the resistors were good so I would look closely at the resistors, I suspect they are open.
This should help you:

¸
So what do i need to do?

[jetadm123]

Re: LG 32LN575S No power Blown fuse.

If you see no reading for R106 and R107, remove them and check them out of circuit.

[Dragunov]

Re: LG 32LN575S No power Blown fuse.

If you see no reading for R106 and R107, remove them and check them out of circuit.

Desoldered them still no reading...

[R_J]

Re: LG 32LN575S No power Blown fuse.

So the resistors are open, then I would be 100% the ic is bad. And don't forget R108.

[Dragunov]

Re: LG 32LN575S No power Blown fuse.

So the resistors are open, then I would be 100% the ic is bad. And don't forget R108.

Ok so now comes the difficult part... Find the right parts to order...

Would be much apritiated if you could check with what i can replace...

Q101 MDF11N65B http://elmatis.hr/Products.aspx?categoryId=445

IC101 SC1S311A http://elmatis.hr/ProductDetails.aspx?productId=28802

R113 0.25 Ohms 5% http://elmatis.hr/Products.aspx?categoryId=73

R106, R107, R108 http://elmatis.hr/Products.aspx?categoryId=248

[R_J]

Re: LG 32LN575S No power Blown fuse.

The ic seems to be correct, I'm not sure which mosfet you are using?
any 0.25Ω 1 or 2 watt should be ok, and for the source resistor (seems you have a choice of 0.22Ω) It should be ok

you need to measure the size of the smd resistors on your board, 1206 are 3.2mm X 1.6mm