Please help power supply problem

[Neotheone]

Hi, posted before and help was given but still having problems - I have a 42" alba tv that went pop so checked for bad caps but identified none that where obvious, anyway f800 t 3.15a 250v fuse blown replaced and blew again - I also have another board bought from ebay but was slightly different (little difference in cap type and extra power connector. taking reading from the bridge rectifier and as you would think the apparent good board only measures correct on way only but the other shows measurement in both directions (in circut) taken them both out and they measure fine - one way only > why in circut does the faulty board bridge rectifier show both ways ??? open/short nearby and if so what ??
17pw26 3 power board known pain in the backside i have heard... any help would be helpful - thanks

[Neotheone]

Re: Please help power supply problem

Hi, these are the two boards one with note on is apparently good boar but are they comparable?

[Neotheone]

Re: Please help power supply problem

see pic - items burn and also no power from when son inserted scart lead when switched on .. thanks again

[tom66]

supply problem

You have a Vestel power supply, and probably a Vestel TV with the Alba name on it. Sadly, Vestels are the Lada of the TV world, absolutely rubbish.

The most common cause of this problem with Vestel TVs is the PFC MOSFET and/or diode going short circuit. These often fail due to the big black capacitor going too low in capacitance causing problems with the other components.

The board you have is most likely compatible. As long as the connectors match it shouldn't matter. Manufacturers like Vestel like to play Russian Roulette with their power supplies, shooting off components from a distance until they stop working and then replacing the last component. So it's not uncommon to see boards with tons of missing components.

[Neotheone]

Re: Please help power supply problem

thanks for the advice - if possible would you know why the bridge rectifier would give a faulty reading in the board that has failed but ok in the other board when switched? thanks again

[Toasty]

Re: Please help power supply problem

Because the bridge is not bad. What follows it in the circuit is.

Likely the main switchers.

[Neotheone]

Re: Please help power supply problem

Right - I now have power through the tv main standby light on but when switching on it just flashes ? any advice

[Neotheone]

Re: Please help power supply problem

Update replaced the ic chip and three transistors / mosfets q813 q814 q803 and also cap c380 now I think i have a s/c diode will report back on Sunday having a drink now so I will leave the electrics until tomorrow ..

[Neotheone]

Re: Please help power supply problem

if you look at the mainboard you see a few wires attached and there seems to be a piece metal (half circle) should this be whole (full circle) and what is it for

[Toasty]

Re: Please help power supply problem

It's a ferrite core that is used for interference suppression/filtering. It is broken as it should be a solid ring. It is not the cause of any of these troubles.