Dynex DX-LCD32-09 no backlight

[lookimback]

Picked this up today and couldn't wait to open it up. It gets sound but no picture. Backlights aren't coming on at all. I have 24v to all 24v terminals on inverter board. About 4.5v to inverter on pin. About 3.5v to pdim. So inverter is getting power and turn on signal. As per post 51 of this thread I tested all transformers between pins 4 and 5. Readings are as follows:

1) 1018 ohms
2) 1004
3) 1006
4) 1010
5) 1011
6) 1005
7) 1018
8) 1008
9) 1005
10) 1003
11) 994
12) 1021
13) 1011
14) 999

I also removed all 4 electrolytic caps and tested them. ESR was between 0.04 and 0.06 on all. Only reading that seemed off was the capacitance. They are all 35v 270uf but all had readings of around 290-293uf. Again, they were tested out of the board. I've never encountered caps with capacitance over the specified value so I don't know what to make of it. Any help will be appreciated. Thanks. I'm taking a pic of it now.

[lookimback]

Re: Dynex DX-LCD32-09 no backlight

Here's the pics.

[budm]

Re: Dynex DX-LCD32-09 no backlight

Check that small black fuse F3? with "20' on top, It is very commonly failed fuse, poor quality fuse. 1A fuse 76V you can use PICOII fuse with higher voltage rating.

[lookimback]

Re: Dynex DX-LCD32-09 no backlight

I had tested F201 and F301. I didn't even see that fuse. That's it too. Thanks! I think if you ever come to Buffalo, I probably owe you a lunch or 2. My Mouser order came today too. Got one busy night planned. Parts for 2 TVs and 2 furnace boards.

[budm]

Re: Dynex DX-LCD32-09 no backlight

If that little fuse is open, you can just jump it for now or use .47~1 Ohm 1/4W resistor in its place to try out. More likely that is all it needs.

[lookimback]

Re: Dynex DX-LCD32-09 no backlight

I don't have a resistor within that range. I'll have to order a fuse and see then.

[budm]

Re: Dynex DX-LCD32-09 no backlight

So the fuse is open? I myself never run into this open fuse due to the fault of the circuits yet, none of the running current draw has exceed the fuse rating. You can put your meter in DC Current mode and just put the two probes on the fuse's pads to read the current draw, just do not slip!

[lookimback]

Re: Dynex DX-LCD32-09 no backlight

Yes, its open. Also wondering too about the 4 electrolytic being over the stated rating. 290-293uf but should be 270uf. I've never seen that before. I'm going to replace them anyway but just wondered if that is common and nothing to worry about. They're Nichicons by the way.

[budm]

Re: Dynex DX-LCD32-09 no backlight

I would recap those just for prevention, will not wait for them to fail since they can take out lots of parts on the board with it due to high AC ripple voltage . I bet if you jump that fuse, you will get the backlights.

[lookimback]

Re: Dynex DX-LCD32-09 no backlight

Jump it with the resistor or a piece of stranded wire?

Edit: This may seem like a will question but what is the caulk like substance that the caps are glued to the board with and does it serve a purpose (ex. Heat transfer) other than just holding component in place?

[budm]

Re: Dynex DX-LCD32-09 no backlight

Yes. The silicone like material is used to keeps the cap in place during the wave soldering and also keep them in place during board transition.

[lookimback]

Re: Dynex DX-LCD32-09 no backlight

I figured it was for something like that.

[lookimback]

Re: Dynex DX-LCD32-09 no backlight

Yup, lights came on. I jumped it with a single strand from some stranded wire. Only let it stay on for about 1 second then unplugged it. Didn't want to burn anything up. The fuse you suggested will be in my next order from digikey.

[lookimback]

Re: Dynex DX-LCD32-09 no backlight

Well, I finally found time to fix the inverter board. I soldered in the replacement fuse and it worked like a charm. Getting ready to move into new apartment on the 1st so not much time for the hobby. Can't wait until I get there and can turn the spare bedroom into my shop. That's when the real fun will start.

[lnbf]

Re: Dynex DX-LCD32-09 no backlight

my dynex dx-lcd32-09 does not have F3 cap on the inverter board i took a red marker and look threw magnify glass and marked each part # my inverter board is a DAC-24T042 i looked and looked could not find it F1 and F2 is all i can see if the picture u have here showed the whole board i could find it looked like it was by R13 i found R13 but no F3 Thanks lol

[budm]

Re: Dynex DX-LCD32-09 no backlight

@inbf: which one do you have?
http://www.shopjimmy.com/catalogsear.../?q=DAC-24T042

[lnbf]

Re: Dynex DX-LCD32-09 no backlight

Hi budm its the top one dac-24t042df i checked the transformers solder leads on the top of transformers looking at the board mounted in tv the first trans. on top was open on the solder leads on top of the first trans. all others had a circut can u buy just the transformer its self. that trans. looked like it had a black spot on the copper wire and i wanted to ask u if i checked it right from thows solder leads. thanks

[budm]

Re: Dynex DX-LCD32-09 no backlight

Some those legs of the transformers may have some flux on them, you should resolder all the legs and make the resistance reading again.
If one of the transformer failed, then the symptom will be that the backlights will flash on for seconds then goes off, the OP board is not the same as yours that is why you cannot find that black fuse, when the black fuse failed, you will not see the lamps flash on at all. So how do your lamps react when the TV is first turn on?

[lnbf]

Re: Dynex DX-LCD32-09 no backlight

thats what is happening backlight comes on and shuts off in seconds i well do what you asked tomorow and recheck resistance. thanks lol

[Shane711]

Re: Dynex DX-LCD32-09 no backlight

Well I have this TV and same problem, no backlight. But apparently I must have something different. Same model number but my inverter board is not the same. I found 4 fuses on the inverter board, f1 f2 f3 f4. One has an "N" on top and the other three "P". F3(P) I found to be bad. I have no idea what size fuse this is so if anyone can tell me I would be so thankful. What I did was replace the fuse with a thin piece of solder and now the TV works. Not sure how long this will last but I used the solder because I know it will act as a good fuse. But I want to put a real fuse in it.