[LCD 22' TV] Dead Standby just replaced Faulty Diodes on PS but...

[Ragnar22]

Hey guys, the TV was complitly dead, no standby.
I checked the fuses, caps and diodes.
Diodes were faulty.

I have this power supply: "vestel 17ips61-3"

I replaced all the diodes.
After that, the TV turned on(yeyyyy) but after few seconds it started to smoke...
I turned off and I touched the diodes and 1 diode (D9) was sooo hot.
Dont know what else can I do with this PS whitout buying a new one... Any tips?????


View attachment Power+Supply+17IPS61-3+VESTEL.pdf

 

[BradtheRad]

Diodes burnt apparently, although it's possible they were not the defect, but rather some component is defective so that it passes excessive current, overloading one or more diodes.

Did you spot which component smoked? Was it a diode? It's important that you search the circuit board and locate any burnt components.

Did you detect buzzing from the tv, either from the speaker or the circuit board?

 

[nnaveli]

i dont know that set,but most lcd got psu (power supply unit) that is separated from other parts,u better change the whole psu .

 

[betwixt]

If D9 is overheating you have an overload on the 24V rail.
Check all the resistors and capacitors across D9 and the capacitors between the 24V rail and ground. If they are OK, the fault is probably elsewhere in the TV on the 24V line.

Brian.

 

[Relayer]

Hello Ragnar22,
Firstly, you need to make sure that you've replaced those diodes with the same types or equivalents as shown in the picture below.
To determine if the fault lies in the power supply itself or the problem is further down the line, you need to isolate the 24V rail.
This can be done by lifting one leg or removing a component down the line that supplies the rest of the set with 24 volts.
Once isolated, you need to attach a load to the 24V rail, as shown in the picture below. Polarity of the globe doesn't matter, but it has to be a 24 volt incandescent truck globe.
The 24 volt line may provide several sections to the telly, therefore you need to isolate each section in turn.
Lets say for example the 24V rail goes to a 12V regulator IC, you need to de-solder and isolate the "IN" pin of the device.
Its really a process of elimination to give you an indication of what part/s of the telly are causing it not to work, as well as causing D9 to overheat.
If you do decide to use any of my suggestions please let us know how you get on.
Good luck!!! :grin:
Regards,
Relayer

 

[Ragnar22]

The eletronic store gave me a BY255 to replace a UF5402.

I can't see anything in datasheet pointing that ultra fast spec. Can someone pls confirm this info? Thanks guys.


**broken link removed**

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I am also trying to find cheap PSU's in some internet reseller if I dont suceed in fixing it...

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I changed the D9 to a BYT56 and it works fine, it warms a bit but I think it's normal.
I will let the tv work for the whole morning to make sure there's no overheating problems on that D9.

Thank you so much guys.

 

[betwixt]

BYT56D or higher letter is OK but the 'A' and 'B' versions do not have enough voltage rating. It is normal for them to run warm in operation.

The BY255 is not a suitable replacement. It can handle the voltage and current but not the switching speed so it would overheat quickly.

Brian.

 

[Ragnar22]

BYT56D or higher letter is OK but the 'A' and 'B' versions do not have enough voltage rating. It is normal for them to run warm in operation.

The BY255 is not a suitable replacement. It can handle the voltage and current but not the switching speed so it would overheat quickly.

Brian.

Thanks a lot Brian, I put a byt56-mtfk so I think it's gonna be allright.