TOSHIBA 23HLV87 has fried IC 4419 on PSU

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

https://www.badcaps.net/forum/attach...6&d=1413071836
See those 3 pins that are labeled with 12V? They are the outputs which are connected to the load, so what ever connected to those 3 pins are the loads, so connect the connector back in place and test the resistance between 12V and ground to see what the resistance is.
"testing resistance between ouput pin labeled 12v (going to mb) and any of the pins on the IC, i get shorts" I do not understand why you check between the 12V and any of the pins on the IC. Do you you understand what the load is? The load is connected between the +12v pin and Ground pin.
Do you have power supply that you can hook up the load to such as light bulb, then short out the light bulb (the load) then see what will happen to the power supply? I think you are skipping too much basic electric/electronics here and need to do more readings.
I.E.:
http://101science.com/Radio.htm
http://www.ibiblio.org/kuphaldt/electricCircuits/

[R_J]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

Thats because the ic (fet) is shorted, disconnect the plug going to the main board, then check the resitance from the +12 pin (on the main board) and grouund (on the main board)
If there is no short, locate the F1 fuse on the main board and see if it is ok. if that fuse is ok then it is possible that q04 on the power supply simply shorted and replacing it might fix the tv.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

oh it makes sense there would be no short to the 24v, thats done by Q3, which im guessing i should check for shorts as well

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

budm, if i did that, wouldnt i just fry something on the psu?

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

Shorted switch will not cause reading between 12V OUTPUT and ground to show low Ohm reading resistance because it is just a stuck on switch, the 12V will just be supplying to the load all the time.
Just think about you light switch, if it stuck on, it will not cause the shorts circuit the lamp will just stay on.
The second importand point is that D08 is also shorted out, that diode is connected in reverse bias mode so it will not conduct unless the + Voltage source from some where else is forced fed into the 12V line.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

ok i guess i didnt understand what u mean by shorting out a lightbulb then. what does that mean? if the filiament breaks, the lightbulb is open... but what is shorted?

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

checking resistance on the motherboard between 12v pin and gnd pin (or chassis screw) i get 2.5ohms resistance. i would like to check fuse F1 but in its place it looks like theres just a straight wire...

[R_J]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

Thats right (budm) the shorted fet does not have a path to ground.

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

I will let some one else explain what shorted circuit means to you and what happen when shorts circuit occur.

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

"checking resistance on the motherboard between 12v pin and gnd pin (or chassis screw) i get 2.5ohms resistance." well now you know why the switch burnt out.
12V with 2.5 Ohms load is about 4.8A of current about 57Watts of power dissipation if the 12V can supply that much power.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

no i dont really... are you saying such a low resistance there means something is shorted on the motherboard as well?

and when you say "switch" u mean the 4419 IC ?

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

no i dont really... are you saying such a low resistance there means something is shorted on the motherboard as well?

and when you say "switch" u mean the 4419 IC ?

Basic Ohms law.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

i thought a short circuit means an area of circuit that should have some resistance in it but because a resistor has fused together its like a sold wire and there would be 0 resistance...and we call that resistor "shorted" the opposite of open where the resistance would be infinite... so i think i understand what a short is...yet somehow still confused as to what you're getting at?

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

I will let some one else explain it to you.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

so testing the resistance between the 12v pin and the any gnd pin, tests the entire 12v circuit? and 2.5 ohms is obviously way too low?

on the 5v pin i get 10kohms ... which explains why the 5v part is fine and i still get the red light? half the motherboard is still working?

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

im sorry i dont understand always what exactly you are saying but if you tell me where to put the probes and what measurements to take, and what they mean, i will eventually come to the realizations myself. thank you for all your help so far and continued patience with me!

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

from what i can gather reading and re-reading these posts, is that the psu and the motherboard have issues. something in the 12v circuit of the motherboard went bad, and that somehow caused the ic4419 to be shorted as well?

the mainboard pushed voltage back into the switch and fried it?
not even sure what im saying...

[R_J]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

Something on the main board failed (not a short, 2.5 ohms) causing excessive current to flow, the 4419 mosfet could not handle this current so it failed. Replacing the failed 4419 is the easy part, locating the fault on the main board could take some time. unless you just replace the main board

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

BTW, the diagram has errors on the pin out of the MOSFETs, the DRAIN is the output side not the SOURCE, it is P Channel so the Voltage feeding it should be connected to the Source pin not the Drain pin.
BTW, what is your meter test leads resistance? about 1 Ohms or so?

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

oh great... more complications. what diagram? the datasheet for the 4419 is wrong?