TOSHIBA 23HLV87 has fried IC 4419 on PSU

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

how can i test and repair the damage to the mainboard if all it wants to do is fry the the PSU again?

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

The TOSHIBA.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

thanks budm for the refresh on ohms law, i was forgetting that. but to be honest even if i did those calculations i guess im just not familiar enough yet with what values are acceptable or not...i could have guessed 2.5ohms was too low though, but what kind of range should it usually be in? some k ohms at least?

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

how can i test and repair the damage to the mainboard if all it wants to do is fry the the PSU again?

Look at the diagram where the 12V is fed into and start removing the component or cut traces until the low resistance goes away or use current source and voltmeter for tracing for short, or do a search "how to find short in circuit board"

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

great tips. well i decided to take the motherboard out to look at the backside, not believing that the "fuse" is really just a piece of wire... first thing i noticed right around there 2 ceramic caps are totally blown up!
c169 and c168
are these replaceable?
nice of them in the service manual not to have a components list...
and would i likely have other things wrong as well?

also i dont see in the toshiba service manual where they even give a pinout for the 4419 IC ?

[Caleb]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

Well that could certainly be your fault, you need to remove the one on the right that's blown apart. The one on the left may have survived you will need to check resistance and see if the short has cleared after removing the first. If you still have short remove the other one as well. Make sure you get all the carbon off the board as well or it could cause another fault.

As to the MOSFET the pinout doesn't really matter if you replace it with the same part it will match.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

my fault? how is this MY fault? its always the clients fault!
ha ha just having some fun.
ok well im off to clean this mess up. will get back with the results.
thanks again all you badass badcappers

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

I think he means the fault (bad cap) in the circuit that caused the low resistance reading.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

i know budm i was just trying to make a joke! a play on words u know..fault and fault...anyway..
i cleaned up the area but its pretty bad. the traces have all been revealed and some of them have been broken and lifted. the capacitor just fell off when i started cleaning the area with isopropyl and a napkin...
how can i rebuild something this far gone?

oh and with the cap removed now the resistance between 12v and gnd is 20 ohms ... is this "better" ? but not much...

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

.07 Ohms, can't be, how can it goes lower?

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

sorry i edited it...it DID say .07 but now it says 20...i think because maybe the alcohol was still on there? or idk...maybe i just messed up somehow in the reading...
the other cap reads about 50ohms across it but it jumps around a little

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

20 Ohms is better but still bad. So both caps are removed? Those MLCC (Multi Layer Cermic Cap) when it failed it will usually failed in shorted (very low resistance) out mode.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

no i didnt remove the second cap... should i? im really lost here now that im looking at all these exposed and lifted traces...can i just cut this whole area out and rewire it?

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

I would remove it too.

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

ok i removed the other cap, but it didnt come easily. i had to use solder and flux and after its removed i just have a big mess of solder and try as i might with my cheap "Solder sucker" and desoldering braid, i cant seem to clean it up! now my resistance between 12v and gnd is 50ohms

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

little help here? have i gone too far??

[R_J]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

It looks to me like this board has had some water (or other liquid) damage, by looking at the areas I marked in black. That sure looks like corrosion and could explain why the caps burnt up.

[budm]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

It's time for the new board which may not be worth it for 23" TV.

[Caleb]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

Might as well use it as a practice board to see if you can trace out the remaining faults. Sometimes I have to add flux to the braid to get it to start wicking. It look like the pads are connected by solder bridges still, but there could be other mlcc's shorted as well.

You may want to look up building a current limited source you can apply across the short to see what else gets hot. Its about the only way I've been able to find hidden shorts on main boards

[triplefour]

Re: TOSHIBA 23HLV87 has fried IC 4419 on PSU

yeah ill tell the client and if she donates it to me then maybe ill mess around with it some more... the board is like 50 dollars! robbery for a 23" screen!