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Old 04-16-2012, 01:14 PM   #21
cashkennedy
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Default Re: LCD 32 TV turns off by itself

When replacing caps you need to match the uF fairly closely , but the voltage can be increased because its the maximum safe voltage the capacitor can handle.

So if your replacing a 220uF 10v, you can go 220uf 25v, 220uF 50v, infact its often a good idea to increase the voltage as that makes them last longer ... but you wouldnt want to change 220uf significantly in capacitance (more then 10% or so) so 200 - 240uF.

When you increase the voltage the capacitors often get larger, and looking at those pictures you have very little extra room to work with, so be carefull about size issues.
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Old 04-17-2012, 06:02 AM   #22
Chandyman
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Default Re: LCD 32 TV turns off by itself

Quote:
Originally Posted by cashkennedy View Post
When replacing caps you need to match the uF fairly closely , but the voltage can be increased because its the maximum safe voltage the capacitor can handle.

So if your replacing a 220uF 10v, you can go 220uf 25v, 220uF 50v, infact its often a good idea to increase the voltage as that makes them last longer ... but you wouldnt want to change 220uf significantly in capacitance (more then 10% or so) so 200 - 240uF.

When you increase the voltage the capacitors often get larger, and looking at those pictures you have very little extra room to work with, so be carefull about size issues.
Thanks for that info cashkennedy

Last edited by Chandyman; 04-17-2012 at 06:02 AM.. Reason: name change spelling
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Old 04-17-2012, 06:10 AM   #23
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Default Re: LCD 32 TV turns off by itself

I have noticed that sellers advertise power units under the trade name of the TV it came off, however, i am aware that different TV companies use the same manufactured boards when making their TV's
The board i'm looking for if i was to replace it rather than fix it is a vestel 17PW20.1 - 010507.

My question is this, are all vestel 17PW20.1 - 010507. made to the same spec or is there subtle differences depending on who they are supplying?
If i was to acquire one at low cost from a different branded TV, am i correct in assuming it will be compatible?

Darren
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Old 04-17-2012, 06:15 AM   #24
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Default Re: LCD 32 TV turns off by itself

Quote:
Originally Posted by Chandyman View Post
I have noticed that sellers advertise power units under the trade name of the TV it came off, however, i am aware that different TV companies use the same manufactured boards when making their TV's
The board i'm looking for if i was to replace it rather than fix it is a vestel 17PW20.1 - 010507.

My question is this, are all vestel 17PW20.1 - 010507. made to the same spec or is there subtle differences depending on who they are supplying?
If i was to acquire one at low cost from a different branded TV, am i correct in assuming it will be compatible?

Darren
I have used 17PW15-9 to replace Vestel 17PW20.1 successfully.

There is no difference between variations of 17PW20 supplies as far as I am aware.
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Old 04-17-2012, 06:36 AM   #25
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Default Re: LCD 32 TV turns off by itself

Quote:
Originally Posted by tom66 View Post
I have used 17PW15-9 to replace Vestel 17PW20.1 successfully.

There is no difference between variations of 17PW20 supplies as far as I am aware.
Thanks Tom66,

I have found a replacement part fairly cheaply, from a cost point of view, i will use to replace the part.
Also, i am going to purchase the replacement caps and have a decent attempt at replacing the ones on the old power board for practice, thinking this will give me a spare in case it happens again.

Just a note on an earlier post regarding using a hairdrier to heat the caps, i re fitted the part, put the TV back together again and its stayed on, without switching itself off. I am convinced that this hasn't rectified the problem and before long, it will pack in.

Darren
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Old 04-17-2012, 07:26 AM   #26
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Default Re: LCD 32 TV turns off by itself

Quote:
Originally Posted by Chandyman View Post
I am convinced that this hasn't rectified the problem and before long, it will pack in.

Darren
You never know, maybe a cold joint somewhere and moving the boards
could make it cool instead of cold. Anyway, please update any good or bad news.
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Old 04-17-2012, 08:13 AM   #27
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Default Re: LCD 32 TV turns off by itself

Thanks selldoor,

I will update of any changes and how i get on changing the caps.
I believe that leaving it can cause problems elsewhere, so i will have a good crack at it

Thanks everyone for all your help and suggestions.

Darren
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Old 04-20-2012, 05:27 AM   #28
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Default Re: LCD 32 TV turns off by itself

Quote:
Originally Posted by Chandyman View Post
Thanks Tom66,

I have found a replacement part fairly cheaply, from a cost point of view, i will use to replace the part.
Also, i am going to purchase the replacement caps and have a decent attempt at replacing the ones on the old power board for practice, thinking this will give me a spare in case it happens again.

Just a note on an earlier post regarding using a hairdrier to heat the caps, i re fitted the part, put the TV back together again and its stayed on, without switching itself off. I am convinced that this hasn't rectified the problem and before long, it will pack in.

Darren

Hi,

The next day, the TV started switching itself off again and replaced the power board which seems to have resolved the problem.

I'm still going to have a go at repairing the old power board, I'm told by you trusty gents that the mass production of these cheaply made boards often have cold joints, how easy are they to see?

Think this is the first course of action before i replace all the caps.
the attachment is of the board in question, I would be very grateful if any of you eagle eyed experts see something that i'm missing.

Darren
Attached Images
File Type: jpg IMGP5733.JPG (617.1 KB, 43 views)
File Type: jpg IMGP5732.JPG (721.0 KB, 39 views)
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Old 04-20-2012, 07:03 AM   #29
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Default Re: LCD 32 TV turns off by itself

Vestel 17PW15/20 no power/loses power, possible causes include...

cold joints (as mentioned)
C878/C877 grey caps near main transformer
main cap C902 o/c or lowC or high ESR (should be 150u or more)
two diodes on secondary (big fat ones) - s/c or leaky
s/c or leaky diode for stby
bad caps - two 4700u 6.3V for stby
bad caps - two near upper heatsink 100u 35/50V
bad caps - two small ones near stby
IC828 LM317T bad
78L05 regulator bad for stby
bad slow start MOSFET (SMD, near SG3525A)
controller IC SG3525A bad
o/c or highR PFC feedback resistors - causes low ~325V across cap (should be 392 - 400V)
bad driver transistor for main trafo - three pin TO92 package

In general everything else on these goes wrong before the main output caps fail.

o/c = open circuit
s/c = short circuit

Last edited by tom66; 04-20-2012 at 07:06 AM..
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Old 04-20-2012, 07:11 AM   #30
Chandyman
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Default Re: LCD 32 TV turns off by itself

Quote:
Originally Posted by tom66 View Post
Vestel 17PW15/20 no power/loses power, possible causes include...

cold joints (as mentioned)
C878/C877 grey caps near main transformer
main cap C902 o/c or lowC or high ESR (should be 150u or more)
two diodes on secondary (big fat ones) - s/c or leaky
s/c or leaky diode for stby
bad caps - two 4700u 6.3V for stby
bad caps - two near upper heatsink 100u 35/50V
bad caps - two small ones near stby
IC828 LM317T bad
78L05 regulator bad for stby
bad slow start MOSFET (SMD, near SG3525A)
controller IC SG3525A bad
o/c or highR PFC feedback resistors - causes low ~325V across cap (should be 392 - 400V)
bad driver transistor for main trafo - three pin TO92 package

In general everything else on these goes wrong before the main output caps fail.

o/c = open circuit
s/c = short circuit


Thanks Tom66

Thats wonderful, very informative, thanks.

Is there anything from the pics that is more obvious to the trained eye than mine.
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Old 04-20-2012, 09:42 AM   #31
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Default Re: LCD 32 TV turns off by itself

I have had a look and cant spot anything obvious.
I do have a query - on the back of the board off pin 15 there is f801 which looks like a zero rated resistor. Doubt if its blown but you could check it.
Solder on C853 and C863 looks a bit odd but may just be the pic again IC8241 looks a bit odd and jumpers J809 J801
There is an odd mark righthand side of R890 and at the edge of the board R913/4/5 not sure whats going on there whether they are meant to be joined or not. I will try and find a pic of the same board and see what it looks like. These may all be nothing and just the way the light falls
Really you need good light and a magnifying glass to see.
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Old 04-20-2012, 10:57 AM   #32
vinceroger69
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Default Re: LCD 32 TV turns off by itself

C878/C877 cap legs top right of picture these defently look cold joints imo
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Old 04-21-2012, 08:45 AM   #33
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Default Re: LCD 32 TV turns off by itself

Thankyou for your time gents, i value your opinions.
Will update how i get on.
Darren
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Old 04-28-2012, 10:27 PM   #34
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Default Re: LCD 32 TV turns off by itself

Do you have a close neighbor with the same remote?
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Old 04-29-2012, 02:28 AM   #35
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Default Re: LCD 32 TV turns off by itself

hi chandyman.
just saw this topic and to enforce what tom66 and selldoor stated; these PSUs are really rubbish. repaired 2 TVs which had this one. full of cold joints and bad caps. before inserting the new one, i would repair that too: sure it wont last long, build quality is really poor.
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