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Equipment Repairs => LCD TV forum => Topic started by: mali67 on August 04, 2012,11:33:47

Title: 17pw20 psu problem ? no picture
Post by: mali67 on August 04, 2012,11:33:47

I have an ONN 42" unsure of the model but has the vestel 17pw20 psu.
all voltages seem correct,
problem is when first turned on picture with stay on for upto 5 seconds then go off i still have sound
there are 2 15bf 630v caps that look ok but suspect they could be part of the problem, i dont have any of these to try is thee an equivelent i could try ? could it be something else ?
cheers

Title: Re: 17pw20 psu problem ? no picture
Post by: sparky on August 04, 2012,12:26:39

hi
do the backlites stay on?
dave

Title: Re: 17pw20 psu problem ? no picture
Post by: mali67 on August 04, 2012,12:28:13

no the backlights go off
ive tried another inverter

Title: Re: 17pw20 psu problem ? no picture
Post by: Turnip on August 04, 2012,12:45:38

Hi Mali67,

Would always change those 15nf/630v caps supplying the 24v line feeding inverter - heaps on Ebay. They don't always bulge but are the first things to check - replace anyway, they're cheap - Chris.

Title: Re: 17pw20 psu problem ? no picture
Post by: mali67 on August 04, 2012,13:00:12

cheers chris i looked on the bay but couldnt find any 630v ones, cheers robbie

Title: Re: 17pw20 psu problem ? no picture
Post by: Turnip on August 04, 2012,13:17:12

Hi Robbie,

I didn't either, but got some 1 kv ones from China, bought quite a few so if you want a couple cheap, send an Email - Chris

Title: Re: 17pw20 psu problem ? no picture
Post by: bobi.bt on August 04, 2012,13:18:49

hi mali67
i haved the same problem with with the same vestel supply,and i have changed the 2 caps 15nf with 20nf or 22nf 800v (the voltage could be bigger to,just must to be more than 600v).and the tv work great.
(one of the 2 caps was showing 2 nf measured with instrument.    :051bye:

Title: Re: 17pw20 psu problem ? no picture
Post by: mali67 on August 04, 2012,13:23:06

cheers bob , ill replace them and find out :P
and chris ive mailed you cheers

Title: Re: 17pw20 psu problem ? no picture
Post by: Turnip on August 06, 2012,10:13:41

Hi Robbie,
In the post - honest - Chris

Title: Re: 17pw20 psu problem ? no picture
Post by: mali67 on August 06, 2012,17:21:44

cheers chris , will post a book of stamps off tomorow, will post back with results

Title: Re: 17pw20 psu problem ? no picture
Post by: chrissie jones on August 07, 2012,03:31:02

ive got 18nf in mine.can i replace em with 15nf..

Title: Re: 17pw20 psu problem ? no picture
Post by: Turnip on August 07, 2012,13:35:21

Hi Chrissy,
Folks say 20 / 22nf does the job, never tried but - wouldn't worry too much - Chris

Title: Re: 17pw20 psu problem ? no picture
Post by: chrissie jones on August 08, 2012,03:06:26

thanx turnip...but i used 15nf instead of 18nf and all works fine.

Title: Re: 17pw20 psu problem ? no picture
Post by: mali67 on August 08, 2012,07:42:31

caps arrived (cheers chris) but still same problem , screen flashes on then goes off

Title: Re: 17pw20 psu problem ? no picture
Post by: watteau on August 08, 2012,11:44:21

Hi,
If you've still got the 24v inverter supply when backlights go off, you
could try Q841,D861, or C904, off pin 12, PL802 (the backlight on/off).
Does this voltage change when the backlights go on/off?, possible main pcb
switching inverter off.
Regards,
John

Title: Re: 17pw20 psu problem ? no picture
Post by: mali67 on August 09, 2012,06:13:41

cheers john, 24v is there all the time, i changed the componants you listed , with the same fault :(
all voltages seem to be near enough if not good.
backligts come on for a second or 2 then go off

Title: Re: 17pw20 psu problem ? no picture
Post by: chrissie jones on August 09, 2012,07:31:31

sounds like a faulty transformer on inverter board..

Title: Re: 17pw20 psu problem ? no picture
Post by: mali67 on August 09, 2012,08:03:03

hi chrissie i changd the inverter, with same results

Title: Re: 17pw20 psu problem ? no picture
Post by: Keith on August 09, 2012,09:44:30

Hi,

I think it will probably be a faulty ccfl tube.

Keith

Title: Re: 17pw20 psu problem ? no picture
Post by: mali67 on August 09, 2012,14:08:14

Quote from: chrissie jones on August 09, 2012,07:31:31

sounds like a faulty transformer on inverter board..

Bingo!! Chris, it was infact a faulty transformer on the inverter, i must have put a faulty one back in.
 (serves me right for not checking~) :oops:

Cheers guys  :c017:

Title: Re: 17pw20 psu problem ? no picture
Post by: Turnip on August 10, 2012,12:35:10

Hi and congratulations - but,

You said you'd replaced the inverter - sorry to be picky, but you now admit you hadn't, causing old Quuq (and younger) brains to be stretched for other problems.

Sure it helps fend off degenerative probs - keep it up - Chris.

Title: Re: 17pw20 psu problem ? no picture
Post by: mali67 on August 10, 2012,13:45:33

hiya chris i said in my last comment "i must have put a faulty one in" meaning faulty inverter.
and that i should have checked the inverter i put in first. in other words both inverters must have had the same problem , without me realising
sorry im not very good at explaining things

Robbie

Title: Re: 17pw20 psu problem ? no picture
Post by: mali67 on August 10, 2012,15:28:45

hiya chris, just got access back to my email, it was hacked lol
I hope you didnt think that was me sending you those links , im not that kinda guy :P not my taste, appologies

all the best 

Title: Re: 17pw20 psu problem ? no picture
Post by: Turnip on August 11, 2012,12:50:32

Hi Robbie,

Gals were really great - no complaints at all - trouble is getting down to those tedious tellies again - Chris.