Vestel 17PW19-4 (Intermittent backlight)

[kad]

When I switch on LCD tv Toshiba 23W330DB, the backlight has a continous quick flickering.

I suspected a problem with the Vestel power supply unit 17PW19-4 (see attached pictures).
I first measured the output voltage that goes to the inverter and found around 42Volts there!!! (no load i.e. inverter cable disconected).

Any pointers please?
Thanks, Kad

[tom66]

Re: Vestel 17PW19-4 (Intermittent backlight)

On Vestel power supplies and TVs flickering backlight is often caused by the blue capacitor failing (right next to heatsink - but there are often two), however that usually causes a voltage that is too low, not too high. Try checking it with the inverter plugged in.

Very disappointing to see Toshiba using Vestel power supplies, as Vestel make some of the worst TVs, especially for service/repair.

[kad]

Re: Vestel 17PW19-4 (Intermittent backlight)

I took the blue cap off. It says 47K and 2KV. I took it to a friend who measured it and found 80pF.
Does this mean the cap is good or bad?

Before I put the power supply back in and re-measure the output voltage going to the inverter, I have a silly question. Is it supposed to be a DC or AC 24v voltage coming out of this vestel unit?

Best Regards,
Kad

[tom66]

Re: Vestel 17PW19-4 (Intermittent backlight)

I took the blue cap off. It says 47K and 2KV. I took it to a friend who measured it and found 80pF.
Does this mean the cap is good or bad?

Before I put the power supply back in and re-measure the output voltage going to the inverter, I have a silly question. Is it supposed to be a DC or AC 24v voltage coming out of this vestel unit?

Best Regards,
Kad

I think that is bad.

Can you show a picture of it? I think it's supposed to be 4.7nF.

It's supposed to be DC 24V, usually.

[kad]

Re: Vestel 17PW19-4 (Intermittent backlight)

here is the cap. It looks fine (no cracks,...etc)

Are you sure it's 4.7nF and not 47nF then?

[selldoor]

Re: Vestel 17PW19-4 (Intermittent backlight)

I believe the 47K is 47000pF which is 0.047uF or 47nF

[kad]

Re: Vestel 17PW19-4 (Intermittent backlight)

hmm! I am confused now.
Can more guys confirm this cap value please? blue ceramic drop cap with code 47K?

It's C901 on the Vestel 17PW19-4. Right next to the heat sink.

[tom66]

Re: Vestel 17PW19-4 (Intermittent backlight)

Hmm, that looks like a Y-cap. Where did you find it? Y-caps are safety capacitors, they are not generally critical to the operation of the TV though.

[kad]

Re: Vestel 17PW19-4 (Intermittent backlight)

Please see attached pictures for the location of the C901 cap.
Are you talking about the cuboid blue one in the second picture?

[tom66]

Re: Vestel 17PW19-4 (Intermittent backlight)

Yes, I'm referring to the cuboid one in the second picture. That can sometimes cause this fault.

[alvawilliams]

Re: Vestel 17PW19-4 (Intermittent backlight)

Hi lads, please can anyone tell me what voltages, i am supposed to
get from the 17pw19-4 , i get 24v dc and 10vdc and 33v dc , is that right ?
Thanks
Alva

[selldoor]

Re: Vestel 17PW19-4 (Intermittent backlight)

No data for the board you mention but the 17pw20 which I think may be used instead in some applications has

33v 24v 12v 5v and 3.3v
Welcome to the forum-
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

It will be useful if you can say what the supposed fault was and a bit about yourself - skills tools etc.

[multimeter]

Re: Vestel 17PW19-4 (Intermittent backlight)

do check for dry joints also,vestel are a pain for it