TOSHIBA 23HLV87 has fried IC 4419 on PSU

[triplefour]

this is a repair for a client, and normally i would just replace the board but i cant seem to find a replacement board that looks the same. only one that looks similar and they are not cheap for such a small tv. 40$ at least, for a gamble...unless someone can tell me for sure that this board is compatible:

http://www.ebay.com/itm/Samsung-LN46...item19f4400fae

when i first plugged in the TV it tried to turn on, the power led went from red to green and then died out back to red again. and i smelled that awful smell of electronics burning. but i still have 5v im guessing since the red lights there, but im also guessing that just replacing the IC will just get me another burnt IC unless i know why it failed...
i already checked d08 next to the IC and its fried too. shorted both ways.

any tips on what else to check before replacing this IC and diode?
or should i just chance buying the very similar looking board?

markings on the IC read 4419 BA742D

it says its at board position Q4 but i cant find reference to this chip (Q4 or 4419 or BA742D) anywhere in the schematics.

[dcapper]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

The psu model number is AH302236 or DTV205P.

http://www.moduslinkptstvboards.com/ah302236/ Not in stock

http://www.shopjimmy.com/toshiba-ah3...upply-unit.htm Not in stock

and I don't know if this one will work:

http://www.tristatemodule.com/p-1646...ns-20cltv.aspx

or

http://www.tristatemodule.com/p-1373...0mf251w37.aspx

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

ok i found the part in the schematics that refers to the area in question
they call it Q04 instead of Q4 like on the board.
but what i dont understand is why for an 8 pin IC they dont have a block diagram of where all the pins are going? really have no idea how to read whats going on here.


thanks dcapper but it looks like those boards are missing a major transformer that mine has...

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

"The psu model number is AH302236 or DTV205P."
how did u know the model number? i cant find that anywhere...

on digikey:
typing 4419 BA742D gives me nothing.
typing 4419 gives me a bunch of different types of IC to choose from and i have no idea...

whats the sure way to identify a replacement IC?

[R_J]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

I found this http://jycic.en.alibaba.com/product/...ircuit_IC.html
Looks like the number to use is 4419
I also found AO 4419
http://www.aosmd.com/search?pn=4419
Not sure if it will help


http://www.digikey.com/product-searc...eywords=ao4419

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

hmm but these guys dont seem to offer to just buy one... and putting that part number in digikey i still end up with way too many results
also, how did u find that? because it does look a lot like the one...but they give little more information

[R_J]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

http://www.digikey.com/product-searc...eywords=ao4419

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

well i thank you for your help but without seeing a picture of it, and the schematic not telling me anything, i cant be positive of any of those replacements except the first one which does match up visually. ill keep digging.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

hmm i see the brand is alpha omega, so the ao might be the right one...on that first site, the ap might be a typo?

yes that must be it. thanks! i never would have known that logo stood for "alpha omega"

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

i also have to replace the diode...in the schematic its listed as 1SS184
which seems to be here:
http://www.digikey.com/product-searc...eywords=1SS184

but the picture they show has 3 pins and it looks like on my motherboard this diode only has 2 pins, one at either end...

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

http://www.digikey.com/product-detai...4-1-ND/1855966

[R_J]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

Looks like its just used to switch the +12 volts on and off, there is another one (Q3) to switch the +24 volts, Its only $1.00 plus shipping

Is the diode D08 also bad? that is a seperate part from the mosfet. I suspect that the diode is ok and only the mosfet is shorted, don't be confused with the diode that is accross in the pdf of the mosfet.

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

You should check the resistance on the output side (load) to see if it is feeding into shorted load or not.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

not sure if i follow exactly, sorry... check the resistance between the drains and chassis ground?
i have the psu completely out of the tv...can i check it like that?

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

There is load connected to the 12V output, so you need to test the load side. You have power supply that must supply the power to the load, if the load is shorted out, then what do think will happen to the power supply? Smoke.
That burnt up MOSFET is being used as a switch to supply 12V to the load.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

i guess i just dont understand what you mean by load, and load side...

*breaking down*

where do i put probes?

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

The main board is the load, the inverter board is the load. Look at the diagram to see where that 12V is connected to, those will be the loads.

[R_J]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

The Block diagram shows a fuse (f1) on the 12v/3a on the main board. I would also check the resistance between +12va and ground on the main board

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

so test the resistance between the output of the IC and the output pins of the PSU to the MB and also to the output to the inverter?

which pins of the IC are the output? i know its not gate, but i always get confused with source and drain...is the drain the output of the IC?

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

testing resistance between ouput pin labeled 12v (going to mb) and any of the pins on the IC, i get shorts on all except pin4

doing the same test but with the 24v pins on the inverter connector i get resistances on all pins