DYNEX 40" Model DX-L40-10A/4832 Will not power on.

[rabbit6000]

Hi All, I am new to this forum. I have a basic background in electronics repair from a Computer systems technology course that I took. I have forgotten most of it lol and thus why I need your help please!

Here is the background on this unit,

- 1 year ago was running fine
- gave it to my sister
- 2 months later starting having problems turning on (standby OK, power on and power light would come on for a second or two then back to standby)
- if she unplugged the AC and plugged it back in, would typically come back on. or display a white screen.
- she kept using it like this for 6 months.
- progressively got worse until it now does not turn on. (stays on standby) but you hear the relay click when plug/unplug the AC.
- She gave it back to me, go figure lol

Here is what I have done so far :

- I have checked over all the circuit boards for visibly bad caps and do not see any.

- checked for cold/bad solder joints, found a few that looked suspicious, so de-soldered/soldered them. Still same.

- searched online, and found this great website with GREAT people, badcaps.net

- Found a couple of posts relating to this type of tv/problem, went thru them. most relate to replacing the large blue heat wrapped cap. but mine shows no visible signs of a problem. (although I do not remember how to test them )

- some of them related to problems with the voltage rail on the power board (model : rsag7.820.1673 ver.e), so I checked mine, here are the results with the other boards attached and without (these are done with AC plugged in, without powering on(cause it doesn't lol )):

_________with boards___________without
STB_________2.8v________________0v
5v-s_________4.9v_______________4.9v
5v-s_________4.9v_______________4.9v
12v_________12.8.v_______________0v
12v_________12.8.v_______________0v
BR1__________4.0v________________0v
SW___________0v_________________0v
5v-m_________5.1v______________0.03v
5v-m_________5.1v______________0.03v

I triple checked the readings.

Seems very strange to me that the 12v is present with the other boards attached but not there at all with the boards unplugged ??

And I am not sure the other readings are what they are supposed to be ?

As I said I do have some basic skills at this (from my course, which I have forgotten a lot of. and from fixing blown caps on computer monitors)

I have attached pics. Please take a look and let me know if you see something I am missing here ?

Thanks,
Roger

[tom66]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

There's been quite a few issues with this power supply and it usually turns out to be that blue C842 capacitor. It usually shows very few external failure signs.

[rabbit6000]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

Ok, I will replace it tomorrow if I can get it at my local electronics depot here. If not I will to order it. mine has these markings on it : 2000v 22 nJ do you know of a suitable replacement ?

If there are any other ideas in the mean time, please post here.

Thanks.

[budm]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

Is the connector going to the inverter board has something like 24vdc on it? Since the 12vdc you are getting comes from the same transformer for the 24vdc, then you should have 24vdc at the inverter board.

[rabbit6000]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

I am going to assume that the 24v should be on the longer plug (multicolored not the small white one) since it comes from the power board and the small white one comes from the T-CON

But the problem I have is that I do not see a silkscreen on the pcb denoting which pin is what ? any idea which one is supposed to be the 24v ?

Oh and about my test of the power board rail, after reading a few other threads on this board, it appears that the 12v pins should be staying at or near zero until the power button is turned on ? is this correct ? if yes then I should not be getting the 12v right now since it does not power on ?

Thanks.

[budm]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

That's right, you should have 12V when you hit the power switch, this 12v and the 24v is turn on by the main board using the STB signal pin which you do have 2.8V when you hit the power switch, that is why the 12V is on, at the same time the 24v power supply should be on also.
Can you take the closed up pictures of the inverter board connector so we can see which pin is for the 24vdc feeding for the inverter board.

[rabbit6000]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

ok, I will get a pic up later when I get home from work.

But there is definitely something not right here, because I never pushed the power button when I took those measurements, only plugged in the AC. (maybe this unit defaults to power on ?)

I will see about getting that replacement cap (the large blue one) as well on my way home.

Thank you both for all the help so far, hope to get this fixed soon in the time for Christmas

[rabbit6000]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

apparently I cannot get that cap locally here in Ottawa, the guy at the local electronics parts place thought I was nuts looking for a 2000 V cap, he said he has never heard of a tv that uses one... LOL

Anybody know where I can order a 2000V 22nJ that delivers to Canada ?

And I think I found the 24V line, I will test it shortly, have a few other things to do first.

[rabbit6000]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

Ok, so I have tested the output of the pins going to the inverters. I attached a pic with the results, which are as follows.

Once again, with only the AC attached, haven't touched the power button.

Pins 1-5 have 24v, the second last pin has 5v

So to re-cap with only the AC attached, WITHOUT turning on the unit, I am getting the 5V, 12V and 24V signals. But the unit stays on Standby (red light) no response from the power button on TV or remote. And apparently no backlight at all.

Here were my original reading on the power rail to main board :

_________with boards___________without
STB_________2.8v________________0v
5v-s_________4.9v_______________4.9v
5v-s_________4.9v_______________4.9v
12v_________12.8.v_______________0v
12v_________12.8.v_______________0v
BR1__________4.0v________________0v
SW___________0v_________________0v
5v-m_________5.1v______________0.03v
5v-m_________5.1v______________0.03v

I need to know why BR1 is 4V and why SW is 0V ? seems to me that these are the only weird readings assuming the unit is trying to power on when the AC is plugged in ? Anybody know what the BR1 and SW are for ? and what the proper values should be ?

I found a link to the service manual if it helps :
http://www.scribd.com/doc/72513882/D...ual-DX-L40-10A

But I cannot save it unless I pay for it

[Mr Bill]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

Here is the service manual.

[budm]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

So where is the pictures of the connector of the inverter board?
SW is the BL_ON (backlights ON, should be >2.5VDC
BRI is the backlight dimming control.

[rabbit6000]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

Hi Guys, thank you for all your help so far much appreciated. But it seems I will have to shelf this repair until after Xmas, it is more complicated than I have time for right now with all the holiday running around and planning to do

So I will update this thread once I can concentrate more time on this.

Again Thank You,
Roger

[EMRACING88]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

We are having this problem with this TV did you repair it with any success? Just wondering going to follow all the help here and work on this project tonight

[evelhorn]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

Can someone share with me a good supplier where I can order that c842 cap. I'm having a hell of a time finding one that I know is the correct one.

[budm]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

Can someone share with me a good supplier where I can order that c842 cap. I'm having a hell of a time finding one that I know is the correct one.

Cap on which board? Power supply, main board, etc.?
More details and pictures will get more help.

[mmartell]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

It's the cap on the power supply tomm66 mentions in post#2. Dunno where you get it, tried ebay ?

[budm]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

Thanks martell.
Post #3: 2000v 22 nJ
0.022uf 2KV 5%. High pulse DV/DT.
http://www.digikey.com/product-detai...235-ND/1532455

[evelhorn]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

Thanks budm, I actually found it on another thread. But thanks for the response

[Unspun01]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

Hello:

I just had the opportunity to service this TV Dynex model DX-L40-10A...

When plugged in, a relay would click, and the standby light would illuminate RED, but was completely non-responsive to the remote or the side panel "touch sensitive" buttons.

I just wanted to inform everyone that the root cause of my problem seemed to be that 3 capacitors tested HIGH ESR. They are: C811 (10uF/25V), C812(10uF/25V), and C814 (100uF/35V). C814 was not too bad, but replaced anyway... C811 and C812 wouldn't even register on my ESR meter so they must have been quite bad.

All other caps on this power supply tested ok, including the potential suspect C842 which measured at 22nF...

Thought I'd share this info in case anyone else has same issue and I can save them some time

[evelhorn]

Re: DYNEX 40" Model DX-L40-10A/4832 Will not power on.

OK people bear with me, this is gonna be pretty long. I also have a dx-l40-10a that will not power on, except for the red standby. I first changed the blue c842 cap, that didn't help. So I got a new power board, the light briefly turned blue one time but no picture and it wouldn't after that one time. I then got a new main board. Same thing, the light turned blue with no picture once and never again. I also don't hear the click from the power board when plugged in any more either, but the old will still click. Could the on/off switch be the culprit? Thanks for any insight