Wharfedale LCD42F1080P comes on but then picture turns off

[shepp]

picture comes on then turns off but sounds still there, ive tried to check transformers but havent found anything yet, the transformer boards are CMO I420HI-20B any ideas any one? no bad caps that the eye can see

will post pics if need, but be good if someone can point me in the right direction

Transformers are 4023Q's (cant find data sheet to check what the readings should be)

and cant find service manual for this model of tv

[tom66]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

Good 24V to inverter?

[shepp]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

will test that tomoz, if its low will the back light still come on to start with?

[tom66]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

will test that tomoz, if its low will the back light still come on to start with?

PSU can sometimes start with good 24V and then drop out.

[shepp]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

right tested 24.55 VDC so thats pretty stable

[shepp]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

right ive just measured accross the supply 0V's and i get 21v on the first black wire then 23v on the second black and only 16v on the third black coming from the Power board theres no markings on the board to see what there for but ill post a pic any way in 2mins

the measurments are using one red wire from the 24v + then from right in the pic to left (black 0v)

[shepp]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

pics

[tom66]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

Oh dear. It's a 17PW16. 37/42" LCD PSU.

Report the voltages on connector with orange/blue wires please.

[shepp]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

Oh dear. It's a 17PW16. 37/42" LCD PSU.

Report the voltages on connector with orange/blue wires please.

Is that bad? Lol

From right to left (blue to red)

Standby
1. Blue 5v
2. Orange 3.4
3. Orange 3.4
4-6 black 0 v
7-9 red 1.3V
10 is empty
11+12 red 0.7v

When on 11+12 change to 5v and rest remain same as above

[tom66]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

The 17PW15, 16 and 20 supplies are probably the worst power supplies I have ever encountered in an LCD TV. They are designed and manufactured by Vestel.

Can you post a picture of the inverter?

[shepp]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

this is only pic ive got coz ive put the covers back on to test voltages (model : I420H1-20B-MASTER / SLAVE)

but these are the same on ebay :

http://www.ebay.co.uk/itm/2709597472...84.m1423.l2649

been looking for info on transformers but couldnt find anything, i checked them all and the primarys were all roughly 1kohm within +-10%

when the power comes on it seems like all the bulbs are coming on so i dont think its a bulb out

[tom66]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

It's difficult to tell if a bulb is out on a TV.

But it's rare - most common failure is a transformer or output (fuses, MOSFETs, driver IC...)

Are there any fuses on the board, there are sometimes individual ones for each group of inputs, so check these...

Also check the buttons on the side/bottom panel are not stuck/jammed as I had the same issue with a Bush, would turn off in seconds sometimes (but thankfully not a Vestel.)

[shepp]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

ill have a look tomoro...will the fuses be surface mount ones? ill take some more pics of the invertor boards when i strip it down again tomoz.

just had a quick check through the buttons but they seem to work on push testing unless the contact on the boards dodgy but again will check properly tomoro and get back to you

[tom66]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

ill have a look tomoro...will the fuses be surface mount ones? ill take some more pics of the invertor boards when i strip it down again tomoz.

just had a quick check through the buttons but they seem to work on push testing unless the contact on the boards dodgy but again will check properly tomoro and get back to you

Yeah, the fuses will be SMD.

I used contact cleaner to fix the Bush - no issues, would recommend spraying a bit in there if you have some spare.

You could also unplug the button board to see if it turns off without it plugged in...

[shepp]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

invertor master pics

all 4 fuses on this board are ok

[tom66]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

OK check primaries of transformers too all should measure close to zero.

[shepp]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

i checked through the pins and there the only sensible readings im getting on all the transformers, there isnt really any that sticks out as shorted or open

[tom66]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

Do you see 0.8 ohm on all the transformers?

[shepp]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

ye all are below 1ohm but i have just spotted that when ive reconnected one of the bulbs i bent the pin so when i tested it again it did the same come on then went off, so it might be a bulb gone, ive just put the pin back right and retested and its still doing the same, how do i check the bulbs? with the meter? or shall i just disconnect them one by one and see if it stays on?

[shepp]

Re: Wharfedale LCD42F1080P comes on but then picture turns off

just checked other board, fuses are ok, just gone through the bulbs using the test points and they are all measuring 5.6kohms roughy (within 0.1kohm) on both boards that must be the winding on the transformer tho.