LCD Digital Screen monitor help

[pug_dari]

Hi, first time at this great forum.

Need help regarding a LCD Screen not working the backlight. Only dim picture on screen shown.
Have made a photo of the PCB board and found that one of the transistor PNP (left side on photo marked) has a physical burn out.
Cannot found the part number for both.

TFT LCD Screen
SUPER 808-6B2.PCB

Please help.

[pug_dari]

Re: LCD Digital Screen monitor help

On the board the 2 diodes are marked Q3 & Q4,
Q3 is burn out don`t know what D is
Q4 marked D8-/F8,
What is the replacement in pair for this diodes?

Please help, seams no body want to answer to this post!!!!

[cmj21973]

Re: LCD Digital Screen monitor help

Can you provide brand, make/ model, and or serial #?

[pug_dari]

Re: LCD Digital Screen monitor help

Car Color LCD TFT DIGITAL MONITOR/TV
SUPER - 808
8" SCREEN

808-6B2.PCB
AXJ.05.29

[cmj21973]

Re: LCD Digital Screen monitor help

I am having a hard time finding a schematic for the SUPER sp-808.

Are you sure that they are diodes? Q denotes a transistor (MOSFET).

[pug_dari]

Re: LCD Digital Screen monitor help

I think they are both drain voltage as they have marked with D letter, maybe a sot89 smd need the schematic for that.

[retiredcaps]

Re: LCD Digital Screen monitor help

I agree. They sure don't look like diodes (Q3 and Q4). A diode is D4 (just above the FCON cap on its side).

Are you sure that they are diodes? Q denotes a transistor (MOSFET).

[ecking767]

Re: LCD Digital Screen monitor help

I see two connection that isn't properly inserted. The lamp connection isn't inserted properly. And the LCD screen is connected. just need to confirm you see that.

[PlainBill]

Re: LCD Digital Screen monitor help

Shoot, that's a Royer oscillator!!! Those are definitely NOT diodes, they're transistors. I don't know who made these transistors, but they can be replaced with a pair of the high gain rating Rohm 2SC4672. Also resolder the transformer and make sure that cap is in good shape and soldered properly.

PlainBill

[PCBONEZ]

Re: LCD Digital Screen monitor help

Is there a logo on the part?

[PCBONEZ]

Re: LCD Digital Screen monitor help

My guess is the package has two transistors in it, one D8 and one F8.
D8 = BCF33
F8 = BF824
.

[pug_dari]

Re: LCD Digital Screen monitor help

the right transistor is in good physical condition and can see the device code as shown on the photo
the left side is bun out and the only device code is the letter D....



https://www.badcaps.net/forum/attach...id=16540&stc=1

[PlainBill]

Re: LCD Digital Screen monitor help

My guess is the package has two transistors in it, one D8 and one F8.
D8 = BCF33
F8 = BF824
.

Bad guess. Compare this to the inverter on the Benq monitors. Here's a link to the Benq.

Large poly cap? Check! (C? - obscured by the lines)
Transformer with multiple (three) primaries? Check! (TR1)
Inductor? Check! (L1)
FET? Check! (8 pin package below IC4)
PWM? Check! (IC4) I say it's a TL1451 or equivalent.

I have seen the same circuit (using SMT transistors) in monitors by Viewsonic, Sceptre, and severach even found it in a rack mount Compaq monitor. Look here.

Those transistors can be replaced by Rohm 2SC4672, available from Digikey as 2SC4672T100QCT-ND at $.83 each.

PlainBill

[PCBONEZ]

Re: LCD Digital Screen monitor help

Bad guess. Compare this to the inverter on the Benq monitors. Here's a link to the Benq.

Large poly cap? Check! (C? - obscured by the lines)
Transformer with multiple (three) primaries? Check! (TR1)
Inductor? Check! (L1)
FET? Check! (8 pin package below IC4)
PWM? Check! (IC4) I say it's a TL1451 or equivalent.

I have seen the same circuit (using SMT transistors) in monitors by Viewsonic, Sceptre, and severach even found it in a rack mount Compaq monitor. Look here.

Those transistors can be replaced by Rohm 2SC4672, available from Digikey as 2SC4672T100QCT-ND at $.83 each.

PlainBill

Those use 3-pins, this uses 4-pins.
Probably two transistors in one package with common base or common emitter.

[PCBONEZ]

Re: LCD Digital Screen monitor help

SMD Codes
http://www.google.com/url?sa=t&sourc...kx8BJsyklcP0Rg

[el3ctroded]

Re: LCD Digital Screen monitor help

http://www.mikrocontroller.net/attac...V06_OE5VLL.xls

Updated SMD code list

[PlainBill]

Re: LCD Digital Screen monitor help

SMD Codes
http://www.google.com/url?sa=t&sourc...kx8BJsyklcP0Rg

Looks like (roughly) the same specs as the 2SC4672. Certainly rated for lower power.

It's the same frigging design as used by the Benq!!! Two identical NPN transistors in a Royer oscillator. A TL1451 gating a mosfet to control brightness (and perhaps current?). (No emitter on a mosfet).

Look up the Belinea 101910 service manual.

PlainBill

[PlainBill]

Re: LCD Digital Screen monitor help

Those use 3-pins, this uses 4-pins.
Probably two transistors in one package with common base or common emitter.

I finally figured out what you were saying. You were wrong. The identifier code covers all parts in a package. If it has D8 on one end and F8 on the other one of those codes is the identifier, the other is a date, production, or lot code. Also, the BCF33 is a different package - SOT-23. The package in the picture is the SOT-89 or MPT3 (Rohm's name for their SOT89-like package)

The SOT-89 and MPT3 packages have only three leads. The tab is common with the middle lead. Look up the datasheets.

PlainBill

[PCBONEZ]

Re: LCD Digital Screen monitor help

I finally figured out what you were saying. You were wrong. The identifier code covers all parts in a package. If it has D8 on one end and F8 on the other one of those codes is the identifier, the other is a date, production, or lot code. Also, the BCF33 is a different package - SOT-23. The package in the picture is the SOT-89 or MPT3 (Rohm's name for their SOT89-like package)

The SOT-89 and MPT3 packages have only three leads. The tab is common with the middle lead. Look up the datasheets.

PlainBill

Except when it's made in China by a company that doesn't want their name on it.

[PlainBill]

Re: LCD Digital Screen monitor help

Except when it's made in China by a company that doesn't want their name on it.

Now you are being silly.

PlainBill