Dead Vestel 17IPS71 power board

[london-freddie]

Help please working on a Busy tv I have had give which I believe may have suffered a power surge
Power board seems completely dead no standby light no output voltages that i can find
Input fuse FS1 on board is ok
Anyone any ideas where to start looking now
I know I can just change the board plenty on ebay but would like to at least try and find out what is wrong with this board
will take some pics of the board and post them asap

[london-freddie]

Re: Dead Vestel 17IPS71 power board

17IPS71 power board

[dick_barton]

Re: Dead Vestel 17IPS71 power board

Have you checked what voltages there are across C19, C20, C21 with the meter set to 600V and measure across the two pins of each capacitor in turn.

[diif]

Re: Dead Vestel 17IPS71 power board

Also check the diodes.

[london-freddie]

Re: Dead Vestel 17IPS71 power board

748v on each cap C19/20/21

[london-freddie]

Re: Dead Vestel 17IPS71 power board

any particular diodes to check, are we checking for voltage at diodesor shorts across diodes

[dick_barton]

Re: Dead Vestel 17IPS71 power board

748v on each cap C19/20/21

The readings are incorrect. The capacitors are only rated at 400V DC!!!

[london-freddie]

Re: Dead Vestel 17IPS71 power board

just checked again def showing 747/8 v at + & - legs of caps

[dick_barton]

Re: Dead Vestel 17IPS71 power board

There's no way the voltage across the legs of each capaitor in turn is as high as you say without damage. They are only rated at 400V. It should be somewhere around 340V dc

[london-freddie]

Re: Dead Vestel 17IPS71 power board

meter set at 600V AC red probe on +ve leg black probe on -ve leg 747 or 748v on all three caps if that makes any sense

[dick_barton]

Re: Dead Vestel 17IPS71 power board

meter set at 600V AC red probe on +ve leg black probe on -ve leg 747 or 748v on all three caps if that makes any sense

DC Voltage measurement please.

[london-freddie]

Re: Dead Vestel 17IPS71 power board

am i doing this right ?

[london-freddie]

Re: Dead Vestel 17IPS71 power board

ah 336V DC

[london-freddie]

Re: Dead Vestel 17IPS71 power board

senior moment i think

[dick_barton]

Re: Dead Vestel 17IPS71 power board

Thanks. So you have rectified DC so now to find out why you have no DC outputs.
Could you measure the dc voltage on CN3-CN4 (black connector) with the mainboard disconnected and see if there is at least a standby voltage?

[london-freddie]

Re: Dead Vestel 17IPS71 power board

no voltages at all at CN3/4 connector

[dick_barton]

Re: Dead Vestel 17IPS71 power board

I don't know how close this schematic is but it's time to start checking components.
There are a lot of 0 Ohm resistors that I would check as well.

[london-freddie]

Re: Dead Vestel 17IPS71 power board

sorry but would not know where to start looking

[ReeceyBurger123]

Re: Dead Vestel 17IPS71 power board

Checked the output diodes for S/C ?

[ReeceyBurger123]

Re: Dead Vestel 17IPS71 power board

Please watch my video, yes its a different Psu but same concept:

https://m.youtube.com/watch?v=owmBcJ91yJw