Techwood 37722HD after PSU change still have no backlight

[stevegym]

I have this LCD. Before the power board change, it was not turned on at all. I changed the PSU for a good one, and the symptome is the next: When the tellie turns on, we have a picture just for 1 sec, then the backlight turns off, but you can see the LCD picture from very close, so this means probably the inverter board or the ccfl is the fault. I guess for the inverter.
Have anybody a schematic for this tv or any idea what else can I check.
I will upload a few pictures soon.

Thank in advance for any idea!

[selldoor]

Re: Techwood 37722HD after PSU change still have no backlight

Could be inverter or backlights or even mainboard problem or even the new psu
without further tests it is not possible to tell.
If you have a problem with pictures they need to be jpgs less then 3mb
you can post them using manage attachments.

[tom66]

Re: Techwood 37722HD after PSU change still have no backlight

I have encountered bad inverter transformer on this model before, easy fix. As selldoor says, pictures please.

[stevegym]

Re: Techwood 37722HD after PSU change still have no backlight

There you go. These are from the Inverter. Do we need any more picture from any part?

[budm]

Re: Techwood 37722HD after PSU change still have no backlight

Famous DARFON transformer, check all the transformers
Check the transformer windings resistance between: make sure to report if the reading is shown in OHM, K OHM, or M OHM.
pin 1 & 8 = xxx OHMS
pin 4 & 5 = xxx OHMS
pin 5 & 8 = xxx OHMS

[stevegym]

Re: Techwood 37722HD after PSU change still have no backlight

These are the boards. This is a new PSU on the picture what I bought actually on ebay from a good seller. It was tested.

Thanks in advance for any idea!

[stevegym]

Re: Techwood 37722HD after PSU change still have no backlight

Famous DARFON transformer, check all the transformers
Check the transformer windings resistance between: make sure to report if the reading is shown in OHM, K OHM, or M OHM.
pin 1 & 8 = xxx OHMS
pin 4 & 5 = xxx OHMS
pin 5 & 8 = xxx OHMS

Ok. Give me a few minutes

[stevegym]

Re: Techwood 37722HD after PSU change still have no backlight

pin 1&8= 2,2 Kohms
pin 4&5= 2,2 KOhms but there was 1 transformer where 2,0 KOhms ( I guess it is fine)
pin 5&8= 5,3 KOhms there was one where I measured 5,0 KOhms

[budm]

Re: Techwood 37722HD after PSU change still have no backlight

Around here we figure that it should be within +/-3% from each other, so the 2.2K Ohms +/-3% will be 2266 Ohms on the plus 3% side, 2134 Ohms on the minus 3% side.
I would remove that one with 2K and inspect it closely.

[stevegym]

Re: Techwood 37722HD after PSU change still have no backlight

Ok. I will doublecheck, but there was 3 what have 8-10% from the others. Is it too much difference do you think?

[selldoor]

Re: Techwood 37722HD after PSU change still have no backlight

Unusual to have so many "off" ones what is the part number on them?

Is it one of these http://lcdparts.net/TransformerDetai...ProductID=3269

Perhaps retest just across S1 to S2 and S3 to S4 as mentioned Give result in ohms
as you now know 10ohms can make a difference.
make sure you are getting down to solder on the joints they are sometimes lacquered
Is the battery good in your meter?

The board pic doesnt really show enough - ideally we need the whole board even if its in a few shots
Straight on without flash. I can see 1 fuse but there may be more - can you test those as well.