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Gjackson · 12-06-2025, 09:30 AM

So turns out this is just a run of the mill NPN transistor, it was not the culprit here, a 10uf 25v startup capacitor on the DAP013D was bad, this probably was causing intermittent startups, when I used hot air on the board it probably changed some parameters and by chance the power supply was starting up.

Gjackson · 12-06-2025, 06:24 AM

Was never able to fully resolve it, after I reinstalled the unit it worked fine for around a month when the issue re-appear!

Gjackson · 06-15-2025, 12:51 PM

probed PEX PGOOD while card is on, shows 1.8v which I think is nominal so card should boot. Voltage on PEX rail is 0.88v from the 0.95v I'm injecting, maybe it's sagging too much to power up?...

Gjackson · 02-13-2025, 03:20 PM

I've gone ahead and ordered a couple replacement aat7212 IC's and I'll update everyone when I replace them

Gjackson · 02-12-2025, 04:14 PM

I suppose so, in the meantime thanks everyone for the help!

Gjackson · 02-12-2025, 01:06 PM

Just a quick update, I did exactly that and got the whole set to test with. Plugged everything back in and now it works somehow, I have standby and the tv powers on. I'm a little baffled as to why it's now working. Owner said that it was being intermittent but when I checked it there was no standby at all. There seem to be no cold joints and I tried tapping the boards while in operation and they seem to keep working. The only thing i've done is resolder the eeprom and replace the thermal paste on the CPU. Any clue as to what I should check before reassembly?

Gjackson · 02-07-2025, 10:11 AM

The lamp lights up fine if the mainboard is also connected:

but when I disconnect the mainboard it blinks and doesn't remain steady:

...

Gjackson · 02-07-2025, 08:10 AM

Interesting to note, if I unplug the mainboard from the power supply and take readings again it seems to fluctuate, I don't know if this is intended behavior from the power supply:

A13V = Fluctuating
FAIL_COUNT = 0v
POWER_ON = Fluctuating
PWM_BLU = Fluctuating
OD_ON/OFF = Fluctuating
ANA_DIM = 3.3v

Here's the waveform for A13V when fluctuating:

And for POWER_ON , PWM_BLU, OD_ON/OFF they all virtually look the same as this:

A faint click can be audibly heard with every rise of the waveform...

Gjackson · 02-07-2025, 07:39 AM

Thanks for the reply, with the two boards set up on the bench here are the readings:

while on standby:

A13V = 8.9v
FAIL_COUNT = 0v
POWER_ON = 0.09v
PWM_BLU = 0v
OD_ON/OFF = 0v
ANA_DIM = 0v

while powered on:

A13V = 12.8v
FAIL_COUNT = 3.3v
POWER_ON = 3.3v
PWM_BLU = 0.04v
OD_ON/OFF = 3.3v
ANA_DIM = 0.08v

I'm assuming pin 1 here spells out FAIL_COUNT because I can't really read it

...

Gjackson · 02-06-2025, 06:38 PM

Thanks Lotas,

any clues how I should move forward and what to check next?
For testing I have the mainboard and power supply on my bench connected to each other, it seems like 13v is being generated and the mainboard warms up slowly and then after a while it switches into standby mode 8v and I can't find anything wrong with either of them, 3.3v and 1.8v are generated. Right now I don't have the tv chassis to test with, but maybe the wifi module or t-con board is shorted and was shorting the power supply?...

Gjackson · 11-05-2024, 07:10 PM

Update: removed one of the IC's and the T-CON still get's really hot, nothing changes except the fact that the area of the removed IC on the COF PCB doesn't get hot since the chip is not there

I found this similar report on a website about a Philips tv with identical symptoms. I'm not sure what the issue described is however. There are no cold joints on the IC's and I tried resoldering both and nothing changed.

...

Gjackson · 11-04-2024, 04:13 PM

Hi!

Do you get a standby light? I would start by checking if the PSU outputs 19.45v when it is plugged into the board, from the connector on the small power PCB.

Next If it is present I would check the voltage on those 3 inductors, the grey box looking things on the small PCB

Gjackson · 07-09-2024, 05:52 PM

A bit of an update:

I forgot to mention that those 2 input fuses also measure ok, no indications of a short anywhere. I also desoldered and measured both of the large film caps next to the fuses and they measure good with a multimeter right around their rated 4.7uf.
I also just noticed those 2 white relays which connect the respective live wires, could one of them for some reason not be triggering or maybe damaged? Would it damage the transistor that triggers them If it feed 12v into their coils to test them?

Gjackson · 06-27-2024, 04:39 PM

Bootloop...

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