Dynex DX-22LD 2 seconds to black

[tervel12]

Hi all,

My 22" Dynex LCD TV has the famous 2 seconds to black problem. When the tv is plugged in and powered on, one pair of lamps light briefly. The other pair of lamps get just a little glow to them. After a few seconds, it repeats this and then nothing until it is powered off/on again.

I have tried swapping the lamps and tried a second set of known good working ccfls in both positions and get the same result. So the problem lies only on one side of the inverter circuit but not the other. (The lamps closest to the outside edge are the ones with the problem)

I have replaced most of the caps on the secondary side of the board with the exception of C156 (I just dont have one to replace it with at the moment). I have tested C156 with an ESR meter and the reading is about .03 and it is a 1500uf 25v cap. I dont know the brand, there is just a K printed on the side along with the rating.

I have also checked the voltages on Q205 and Q206 and they have identical readings.

The transformer measures .2ohms on the primary and both secondaries measure around 963ohms.

Can somebody help point me in the right direction please?

Thank you.

[retiredcaps]

Re: Dynex DX-22LD 2 seconds to black

I have tested C156 with an ESR meter and the reading is about .03 and it is a 1500uf 25v cap.

1) I'm not saying this is your problem, but a Panasonic FM 1500uF 25V cap has 15 mohm specs. So yours is 2x.

2) It would help if you posted clear top down view pictures of your boards (both sides) following the instructions in my sig file below exactly.

3) Have you checked the backside for any possible poor or dodgy solder joints especially the inverter transfomers?

[tervel12]

Re: Dynex DX-22LD 2 seconds to black

Attached are the pictures.

[PCBONEZ]

Re: Dynex DX-22LD 2 seconds to black

0 (T)
1 K

Is the date and assembly plant code format used by Chemicon and possibly some of their affiliates like Sam Young.
-
There should be a logo and series name on the other side.
You managed to not show that side on every cap.

Jan 11th and either year 2000 or 2010.
.

[jasbodr]

Re: Dynex DX-22LD 2 seconds to black

I just fixed one of these tv's with the same symptoms & SMPS. Measure the resistance of the primary and secondary on the inverter transformer. My primaries were good but one of the secondaries was outside of the 3% rule posted in previous threads. It was about 9% out.If I remember correctly, the one secondary measured 938 ohms and the other was 1024 ohms.
I also recapped it but I'm betting on the transformer causing the problem. None of the caps showed any visible problems, I just changed them out because of the recomendations of the experts on here. I did check the caps I replaced for value & esr & all were within specs.
You will have to google the part num on the transformer to get the pinouts. 2 of the pins are dummies they aren't connected to anything.

Good Luck

[retiredcaps]

Re: Dynex DX-22LD 2 seconds to black

1) Okay, I think IC201 is OZ9938GN. If yes, the datasheet is at

http://www.datasheet4u.net/download.php?id=638694

2) Pin 16 is your GND.

3) We are interested in measuring the DC voltage of pins 2 (VDDA), 6 (VSEN), 7 (OVPT), 10 (ENA), 12 (SSTCMP).

[tervel12]

Re: Dynex DX-22LD 2 seconds to black

1) I'm not saying this is your problem, but a Panasonic FM 1500uF 25V cap has 15 mohm specs. So yours is 2x.

2) It would help if you posted clear top down view pictures of your boards (both sides) following the instructions in my sig file below exactly.

3) Have you checked the backside for any possible poor or dodgy solder joints especially the inverter transfomers?

I have posted pics of the cap in question. I have also measured it again and if I leave the ESR meter on for a few seconds, it goes down to a measurement of .00.

I have also gone through and resoldered the joints on the transformer.

I just fixed one of these tv's with the same symptoms & SMPS. Measure the resistance of the primary and secondary on the inverter transformer. My primaries were good but one of the secondaries was outside of the 3% rule posted in previous threads. It was about 9% out.If I remember correctly, the one secondary measured 938 ohms and the other was 1024 ohms.
I also recapped it but I'm betting on the transformer causing the problem. None of the caps showed any visible problems, I just changed them out because of the recomendations of the experts on here. I did check the caps I replaced for value & esr & all were within specs.
You will have to google the part num on the transformer to get the pinouts. 2 of the pins are dummies they aren't connected to anything.

Good Luck

I remeasured the inverter transformer and now I am getting 953-956 ohms on pins 1 and 2 and 986-1005 ohms on pins 3 and 4. The secondary should be 960 ohms. Which kind of makes it sound like the transformer is out of spec since it is over 3%.

1) Okay, I think IC201 is OZ9938GN. If yes, the datasheet is at

http://www.datasheet4u.net/download.php?id=638694

2) Pin 16 is your GND.

3) We are interested in measuring the DC voltage of pins 2 (VDDA), 6 (VSEN), 7 (OVPT), 10 (ENA), 12 (SSTCMP).

IC201 is OZ9938GN. Measuring from pin 16 to the mentioned pins, I got the following readings:

pin2 = 5.35v
pin6 = 0v
pin7 = 2.11v
pin10 = 5.3v
pin12 = 0v.

So from all signs, it appears that the transformer is bad. The one side of the secondary is 3-4.5% above what it should be. Would this be correct?

[retiredcaps]

Re: Dynex DX-22LD 2 seconds to black

I remeasured the inverter transformer and now I am getting 953-956 ohms on pins 1 and 2 and 986-1005 ohms on pins 3 and 4. The secondary should be 960 ohms. Which kind of makes it sound like the transformer is out of spec since it is over 3%.

I initally ignored the transformer because in post #1 you said both were around 963 ohms which is the "correct" value if you follow

http://lcdparts.net/TransformerDetai...ProductID=4010

If you are now getting 986 to 1005, I suggest desoldering this transformer and remeasuring out of circuit.

960 x 1.03 = 988.8 ohms

A replacement is available on ebay for $13 + free shipping. The part comes from Brooklyn, USA.

[tervel12]

Re: Dynex DX-22LD 2 seconds to black

I initally ignored the transformer because in post #1 you said both were around 963 ohms which is the "correct" value if you follow

http://lcdparts.net/TransformerDetai...ProductID=4010

If you are now getting 986 to 1005, I suggest desoldering this transformer and remeasuring out of circuit.

960 x 1.03 = 988.8 ohms

A replacement is available on ebay for $13 + free shipping. The part comes from Brooklyn, USA.

Those were my initial readings. Now it is measuring higher on the one secondary.

I desoldered it and remeasured. One secondary is measuring around 953ohms. The other secondary is 1045ohms. Well outside of the 3% so I ordered a replacement.

I will update once I get the replacement and install it.

Thanks a ton to all who contributed!

[tervel12]

Re: Dynex DX-22LD 2 seconds to black

Got the new transformer today and just finished installing it and it works GREAT!!!

Thanks to everyone who contributed! This is the greatest, most knowledgeable forum!!

Thanks again!!!

[tom66]

Re: Dynex DX-22LD 2 seconds to black

Great to hear you fixed it. A strange case of a transformer just being slightly out and causing major problems. Interesting...

[MisterD]

Re: Dynex DX-22LD 2 seconds to black

I have this same model tv going 2 seconds to black, using the flashlight trick I can see a picture on the screen with no backlight, I measured the inverter transformer and got 919 ohms on pins 3-4 and 962 ohms on pins 1-2, I'm hoping that replacing the transformer will fix the problem, any comments are appreciated.

[MisterD]

Re: Dynex DX-22LD 2 seconds to black

Ordered a replacement inverter transformer ( TMS94481CT) got it and installed it today, tv works great now, I rechecked the old transformer out of circuit got 926 ohms on pins 3-4 and 984 ohms on pins 1-2, the new transformer as expected had exactly the same reading of 964 ohms on both sets of pins 1-2 and 3-4...I'm very thankful for this Badcaps forum, I probably wouldn't have thought to check for mismatched resistance on the secondary windings of the inverter transformer.

[rs120]

Re: Dynex DX-22LD 2 seconds to black

Same problem here, I thought it was bad caps, found this thread and sure enough it was the transformer. Had 985 on one side and 1.2M on the other. Found a cheap replacement on eBay and now its good as new. I also changed a few capacitors and re-did a few solder joints that probably wasn't necessary but felt it couldn't hurt. Thank You!