Dynex DX-22LD150A11 please wait, then black screen

[RogueCapacitor]

Hi all,

I have taken a look over the power supply and main logic board, nothing stands out to my inexperienced eyes.

I was hoping we could first rule out if it's the power board or not? here are my readings of the power:
DIM -> 0.03v
BL_ON -> 0
Lamp_ERR -> 0
SGND -> 0
SGND -> 0
SGND -> 0
SGND -> 0
12V -> 12.22v
12V -> 12.22v
12V -> 12.22v
12V -> 12.22v
5VSB -> 5.01v

I don't know what's suppose to be the correct voltages, but I would imagine BL_ON should be higher than 0?

Please help!

[newtothis]

Re: Dynex DX-22LD150A11 please wait, then black screen

So backlights initially come on then go off, correct?

Can you still see an image using a flashlight on the screen?

[budm]

Re: Dynex DX-22LD150A11 please wait, then black screen

Pin 1: DIM -> 0.03v
Pin 2: BL_ON -> 0
Pin 3: Lamp_Err, Not used, empty pin.

So the BL-ON and the DIM are basically not there from the main board.

[RogueCapacitor]

Re: Dynex DX-22LD150A11 please wait, then black screen

Hi guys, thanks for your response!

Can you tell me what it means to not have BL-ON and DIM?
How do I figure out which component is causing this?

[newtothis]

Re: Dynex DX-22LD150A11 please wait, then black screen

BL_ON switches the Backlights on, DIM is the brightness, Usually 1v to 5v from low to high.

Due to the fact all other voltage is present it points to the main being faulty

[RogueCapacitor]

Re: Dynex DX-22LD150A11 please wait, then black screen

Sorry I'm really new to this,
but the main board is the one with all the video and audio inputs?

is it possible there are cold soldering points that's causing this?
Also, if it is the main, can you suggest what I should do now to isolate the component on the main?

Thanks so much for all your help.

[RogueCapacitor]

Re: Dynex DX-22LD150A11 please wait, then black screen

Also, I'd like to add that when I took those voltage readings all other boards were disconnected from the power board.

[newtothis]

Re: Dynex DX-22LD150A11 please wait, then black screen

Also, I'd like to add that when I took those voltage readings all other boards were disconnected from the power board.

Oh, That makes a difference.

Connect all board and recheck pins

[budm]

Re: Dynex DX-22LD150A11 please wait, then black screen

Also, I'd like to add that when I took those voltage readings all other boards were disconnected from the power board.

That is very IMPORTANT info.
Hook everything back together, have meter connected to BL-ON pin then plug the TV into the outlet and turn on the TV to see if the DCV is present and then goes away or it stays at >2.5VDC.

[RogueCapacitor]

Re: Dynex DX-22LD150A11 please wait, then black screen

Hi all,

So I have hooked up my the main board to the power board, and the panel to the transformers? (I'm not sure what they're called, but they're the 4 white little nobs that power the backlight on the LCD.

The voltage of the BL_ON is 3.25 when I hit the power button to turn it on.
The back light will flicker on for a second, then turn off, then flicker on again and turn off again right away. The power stays constant at 3.25v.
The voltage for DIM is also 3.25.

As you can see, I did not connect my ribbon to the panel, I hope that doesn't make a difference?
Is it possible that whatever is trying to power my backlight isn't getting enough power and hence it goes off and on?

[RogueCapacitor]

Re: Dynex DX-22LD150A11 please wait, then black screen

opps, sorry, I forgot to upload the photos.
As you can see, I did not hook up my ribbon, does that make a difference?

I'm wondering if it's my transformer on the power board that's bad?
Is the transformer the one with the yellow tape around it?

[vinceroger69]

Re: Dynex DX-22LD150A11 please wait, then black screen

Hi can you check the resistance on the inverter transformer using this link to show you the pins to check
http://www.lcdparts.net/TransformerD...ProductID=4010

[RogueCapacitor]

Re: Dynex DX-22LD150A11 please wait, then black screen

Hi vinceroger,

I'm afraid I'm very new at this so I thank you in advance for your patience but which pins do I check against?
Do I hook up my black lead on the multimeter to S1 and the red lead to P1?
Or were you wanting me to get the readings from:
P1 -> S1
P1 -> S2
P1 -> S3
P1 -> S4

and then:
P2 -> S1
P2 -> S2
P2 -> S3
P2 -> S4

??
Thanks!

[vinceroger69]

Re: Dynex DX-22LD150A11 please wait, then black screen

Hi vinceroger,

I'm afraid I'm very new at this so I thank you in advance for your patience but which pins do I check against?
Do I hook up my black lead on the multimeter to S1 and the red lead to P1?
Or were you wanting me to get the readings from:
P1 -> S1
P1 -> S2
P1 -> S3
P1 -> S4

and then:
P2 -> S1
P2 -> S2
P2 -> S3
P2 -> S4

??
Thanks!

I may be wrong but test p1 to p2 should be 0.2 ohm
then test s1 to s2 then s3 to s4 should be 960 ohm if this test is wrong someone will correct us its ages since ive tested one of these to be fair.
Please note these tests are with power NOT CONNECTED as this is a resistance test.

[RogueCapacitor]

Re: Dynex DX-22LD150A11 please wait, then black screen

Hi there,
In the picture I highlighted where I think the transformer is?
I'm not sure which is P1 vs S1, but looking at the spacing of the pins, I think 1,2,3,4 are S1, S2,S3,S4
and 9,8, and 7,6 are P1, P2?

Here are my measurements:
1-2: infinite resistant (show's up at 1 on my meter)
3-4: 960ohms
7-8: 0.2ohms

On a side note: If you zoom into the picture, you'll see that 7 and 6 are soldered together, but in 9 and 8, there's a small gap between them? Does this matter?

So I'm guessing that since 1-2 does not have continuity, that means there's a break in the transformer? and by replacing it, in theory it should fix my issue?

Thanks for your help!

[vinceroger69]

Re: Dynex DX-22LD150A11 please wait, then black screen

can you unsolder the transformer and retest does look like pins 1@2 maybe at fault.

[selldoor]

Re: Dynex DX-22LD150A11 please wait, then black screen

yes you are both correct you should be testing pin1 to pin2 and pin 3 to pin4 with no power to the board and meter on ohms 2000.
Looking at your picture the soldering doesnt look great on the transformer so it will need reflowed.
Also the pins are sometimes lacquered so if you have not yet taken it off try again but
dig into the solder with the point of the probe.

[RogueCapacitor]

Re: Dynex DX-22LD150A11 please wait, then black screen

Hey all,

I have finally been able to unsolder the transformer, and pins 1 to pins 2 still read infinity, so most likely this is a faulty unit?

I was wondering, how did everyone know that the issue could be with the transformer by me saying my backlight was blinking off and on?

Also, my transformer says:
TMS94481CT
10TM13 B

What is the 10TM13B? The first line of my transformer is the same as in this picture: http://www.lcdparts.net/TransformerD...ProductID=4010
however the second line is different, what part number do I go off when I order a new transformer? is it possible to repair this transformer?

Thanks,

[selldoor]

Re: Dynex DX-22LD150A11 please wait, then black screen

Yes - most likely faulty if you have tried again off board.

One thing - get a magnifying glass and just check the very thin wire has not just broken off where it is attached to the pin. Unlikely but one membre did once find this and was able to repair. otherwise it is not really repairable.

We have seen this problem many times before.

The second part of the number is just maunfacturers info batch number
production date and so on.

If you can wait they are available on ebay here is one - think I have used him before.http://www.ebay.co.uk/itm/1PCS-Trans...#ht_3767wt_838

You may be able to find others in US

[vinceroger69]

Re: Dynex DX-22LD150A11 please wait, then black screen

Yes ive had/seen a few of this type of inverter fail in my short time of repairing electronics when you receive your replacement transformer check the resistance before you fit it as ive saw a brand new transformer arrive faulty.