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Philips TV no power 22pft4031/05

SAMyMAS

Apr 8, 2023
8
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Apr 8, 2023
Messages
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Hello All,

The TV switched off itself and now there’s no reaction on power button either from TV or remote control.

The visual check of power/mainboard board did not reveal any issues. The photos along with the service manual are attached. The fuse is intact.

Any thoughts/ideas would be greatly appreciated.

Thank you



The manual
 

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Delta Prime

Jul 29, 2020
1,810
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Jul 29, 2020
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1,810
Hello there:)
Could be a game of lights and shadows. Looks
like corrosion can you verify?


photo_1681055120496.png

photo_1681055505867.png
 

Martaine2005

May 12, 2015
4,905
Joined
May 12, 2015
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4,905
First, check whether voltages are present.
Then check for open circuit diodes on the power supply.

Martin
 

SAMyMAS

Apr 8, 2023
8
Joined
Apr 8, 2023
Messages
8
@Martaine2005,

Hello Martin,

-The voltages readings are ~6V, where suppose to be 12V from the power board (Power out, connector CN9101
11/12 +12V
5/6/7/8 GND
9/10 +12V Audio
13/14 +12VA)

-The diodes open circuit are checked, excluding BD9901 bridge (would require remove from PCB).
D9107 (SR515), reads as - Continuity/Short, so have to be replaced.

Zener diode ZD9102 (GDZJ33B) reads in both directions 0.564 direct/ 0.576 indirect, perhaps needs to be replaced too.

I checked also MOSFET Q9101 (STF6N65K3) seems fine, though I am not 100% sure.

The components measurements were taken in circuit (not removed from PCB), while capacitors discharged.

Could you advise if there is anything else I should look before the diodes replacement, please.


Kind Regards,
SAM
 

Bluejets

Oct 5, 2014
6,865
Joined
Oct 5, 2014
Messages
6,865
You will not get correct readings on components in circuit.
Forget the suspect diodes etc until you can at least pull one leg.
The voltages readings are ~6V
Where do you get AC voltage from...????
Be careful what you use as a common reference, it could either be lethal or completely misleading.
I suspect, as you have no indication (assume that is what your first post implied) you have the missing start up voltage ( around 5v DC on the main power board.)
 

SAMyMAS

Apr 8, 2023
8
Joined
Apr 8, 2023
Messages
8
@Bluejets,
Thank you for your follow up to this.

I will revert back once the readings taken per your advise - components out of circuit.

The voltages have gotten from the connector, output from power board towards to main board. They were DC of course, the tilde ‘~’ sign meant to indicate that the readings were floating.

IMG_2434.jpeg

IMG_2436.jpeg


That’s right the tv has no indication…
 

SAMyMAS

Apr 8, 2023
8
Joined
Apr 8, 2023
Messages
8
Hello All,

The reading of diode out of circuit is the same

D9107 (SR515), reads as - Continuity/Short, so have to be replaced.

Could you advise if there is anything else I should look before this diode replacement, please.


Kind Regard
 

SAMyMAS

Apr 8, 2023
8
Joined
Apr 8, 2023
Messages
8
Hello All,

I am glad to inform you, that the repair is successful and the TV is back to use again. And what is more it has been modified to mitigate the issue recurrence.

Thank you ‘MAKER PRO’ and all participants for your assistance and support.

The issue was the diode D9107, which replacement fixes the output power 12V. As you can see on the photo D9109 is not installed at manufacture. However it would appear designers predicted the failure of diode, so the PCB have two slots connected parallel. Thus I installed the missing one. I bought 20 pcs of SR515 and it costed me less than €3 on Aliexpres.

Conclusion:

The approach advised by ‘Martaine2005’ is right. The powers and diodes to be checked first. The diodes removal from circuit to take readings are unnecessary/impractical. However once suspected components identified removal is required to confirm their failure, as advised by ‘Bluejets’

Note,

The TV case closed on plastic clips. Pry tool/s require.

Warning,

The capacitor C9801 has over 300V !
 

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