tps51225c issue

[rookieme]

Hi,
I have a LA-9981p with liquid damage.
The 5 and 3 V were missing and VIN pin at tps51225c was burned so I replaced the tps and connected the VIN line.
Now the regulator is burning hot and I get no voltage at PL100 & PL101.
So far I have removed kbc, all 4 upper & lower mosfets of tps51225c, open pads PJP100 - 103 and replaced again with a new regulator.
The tps still burns hot, I get no short at VREG3 or VREG5 and I get the 3,2 and 5V stable at their pins.
Anyone have an idea what to try?

[caspian]

Re: tps51225c issue

how much voltage is on Vin now?
have you checked tps51225's pins for being shorted together or to ground?

[rookieme]

Re: tps51225c issue

vin = 17,4V
So far I've checked all pins and there is non shorted to ground.
From optical inspection non of them is shorted with the next one also
What could cause tps to overheat as VREG3 & VREG5 are the only outputs now and non of them is shorted?

[caspian]

Re: tps51225c issue

Vin may be still shorted.
how much resistance-to-gnd is on Vin?
is there any voltage on PL100 and PL101?

[rookieme]

Re: tps51225c issue

vin~ 73kohm
PL100 & PL101 are both 0V as I have all four mosfet removed

[caspian]

Re: tps51225c issue

it is normal for tps51225 to get a bit warm.
how much voltage is on DC-jack?

[rookieme]

Re: tps51225c issue

dc-jack gets 19,6 V
tps51225 get hot enough so you cannot hold your finger on it, somehow it manages to get that way for a long time without get burned [gives stable 5V and 3V at VREG3 &5]

[mielta]

Re: tps51225c issue

Hi
remove PL100 and PL101 und check short to ground
give with a laboratory power supply 3v behind PL100 and check amp

[rookieme]

Re: tps51225c issue

Even with both coils removed the regulator still run hot to touch.
Currently I don't have such power supply, the resistance to ground at the output of PL100 is 15 kohm but at PL101 is only 37 ohm.
The fact is that when I give power at that linw with the help of a l-ion battery nothing gets hot.



update:
I removed pu800 and it's upper mosfet any short at 5V line is gone
tps still runs hot

[mcplslg123]

Re: tps51225c issue

Try replacing ene 9012. Will require programming after install with programmer like RT809 or svod etc.

[caspian]

Re: tps51225c issue

I think you measured resistance-to-gnd on Vin by mistake. please measure it again to make sure.
if it did not solve the problem, the next step will be removing PL102. then check whether TPS gets hot or not. then, measure resistance-to-gnd on the two pads under PL102.