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Old 05-03-2016, 03:36 AM   #1
london-freddie
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Angry Dead Vestel 17IPS71 power board

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
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Old 05-03-2016, 03:41 AM   #2
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Default Re: Dead Vestel 17IPS71 power board

17IPS71 power board
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Old 05-03-2016, 03:51 AM   #3
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Default 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.
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Old 05-03-2016, 03:52 AM   #4
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Default Re: Dead Vestel 17IPS71 power board

Also check the diodes.
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Old 05-03-2016, 03:56 AM   #5
london-freddie
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Default Re: Dead Vestel 17IPS71 power board

748v on each cap C19/20/21
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Old 05-03-2016, 03:59 AM   #6
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Default Re: Dead Vestel 17IPS71 power board

any particular diodes to check, are we checking for voltage at diodesor shorts across diodes
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Old 05-03-2016, 04:14 AM   #7
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Default Re: Dead Vestel 17IPS71 power board

Quote:
Originally Posted by london-freddie View Post
748v on each cap C19/20/21
The readings are incorrect. The capacitors are only rated at 400V DC!!!
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Old 05-03-2016, 04:25 AM   #8
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Default Re: Dead Vestel 17IPS71 power board

just checked again def showing 747/8 v at + & - legs of caps
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Old 05-03-2016, 04:39 AM   #9
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Default 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
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Old 05-03-2016, 04:46 AM   #10
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Default 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
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Old 05-03-2016, 04:48 AM   #11
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Default Re: Dead Vestel 17IPS71 power board

Quote:
Originally Posted by london-freddie View Post
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.
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Old 05-03-2016, 04:59 AM   #12
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Default Re: Dead Vestel 17IPS71 power board

am i doing this right ?
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Old 05-03-2016, 05:00 AM   #13
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Default Re: Dead Vestel 17IPS71 power board

ah 336V DC
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Old 05-03-2016, 05:01 AM   #14
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Default Re: Dead Vestel 17IPS71 power board

senior moment i think
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Old 05-03-2016, 05:04 AM   #15
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Default 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?
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Old 05-03-2016, 05:07 AM   #16
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Default Re: Dead Vestel 17IPS71 power board

no voltages at all at CN3/4 connector
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Old 05-03-2016, 05:18 AM   #17
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Default 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.
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Old 05-03-2016, 09:02 AM   #18
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Default Re: Dead Vestel 17IPS71 power board

sorry but would not know where to start looking
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Old 05-03-2016, 09:13 AM   #19
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Default Re: Dead Vestel 17IPS71 power board

Checked the output diodes for S/C ?
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Old 05-03-2016, 09:15 AM   #20
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Default 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
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