I have this apex ld4088, the backlights will run for about 60 seconds and shut down, when they are working there is a slight buzz from inverter board. Power board is out putting the proper voltage. Standby 5v and the 24v to back light inverter board. 24v still present at plug on inverter when back lights quit. Thanks Michael
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Apex LD 4088 backlight shut down
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Re: Apex LD 4088 backlight shut down
One of the lamps or transformers on the inverter board may be failing. You need to look very carefully when the backlights are on to see if you have a dimmer line across the screen where a tube may be failing.
Do you still have an image on the screen when backlights fail if you shine a light on the screen and look carefully.Last edited by dick_barton; 09-29-2020, 04:48 AM.Willing to help but I'm no expert.
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Re: Apex LD 4088 backlight shut down
https://www.badcaps.net/forum/attach...3&d=1601342388
Are the Inverter board mounting screws missing?
Inspect the Inverter transformers as suggested, also unplug the inverter board from the socket and inspect the inverter board fingers and the sockets.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: Apex LD 4088 backlight shut down
Can you check the winding resistance of each of the inverter transformers and compare them to each other.
You said the set powers up briefly so are you able to see if there is a lighter band across the screen where one of the tubes may be failing?Willing to help but I'm no expert.
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Re: Apex LD 4088 backlight shut down
these testers work well i have one myself
https://www.ebay.co.uk/itm/100-NEW-C...wAAOSwZ6tfRMou
this video maybe worth a watch shows how too test ccfl and also the transformers
https://www.youtube.com/watch?v=KCTVaW2XQ1o&t=1233sLast edited by vinceroger69; 09-30-2020, 09:51 AM.
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Re: Apex LD 4088 backlight shut down
Originally posted by dick_barton View PostCan you check the winding resistance of each of the inverter transformers and compare them to each other.
You said the set powers up briefly so are you able to see if there is a lighter band across the screen where one of the tubes may be failing?
1 and 3?Last edited by Hornnumb2; 09-30-2020, 01:36 PM.
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Re: Apex LD 4088 backlight shut down
Originally posted by Hornnumb2 View PostWhich terminal do I test across in this pic? https://www.dropbox.com/s/lkcm3859pj...D4D00.png?dl=0
1 and 3?
What's the inverter board part number?Last edited by dick_barton; 10-01-2020, 12:37 PM.Willing to help but I'm no expert.
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Re: Apex LD 4088 backlight shut down
There appears to be 4 solder points on each transformer.
If you label them 1 to 4 then test
Transformer 1
Pin 1 - 2
Pin 1 -3
Pin 1 - 4
then
Pin 2 - 3
Pin 2 - 4
then
Pin 3 - 4
Transformer 2
.
.
.
And note the resistance carefully for each test and for each transformer 1 to 10.
It would also be worth looking on the underside of the board to see if there is any sign of overheating. Board tends to brown.Last edited by dick_barton; 10-01-2020, 01:02 PM.Willing to help but I'm no expert.
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Re: Apex LD 4088 backlight shut down
Ok here we go.
1) 1-2 8.45 2) 1-2 8.27 3) 1-2 8.67 4) 1-2 7.9 5) 1-2 8.67
1-3 .03 1-3 .03 1-3 .03 1-3 .02 1-3 .03
1-4 8.3 1-4 7.09 1-4 7.8 1-4 8.62 1-4 8.3
2-3 8.4 2-3 8.38 2-3 8.01 2-3 8.5 2-3 8.3
2-4 .4 2-4 .4 2-4 .4 2-4 .4 2-4 .4
3-4 8.6 3-4 8.07 3-4 8.39 3-4 8.56 3-4 8.1
6) 1-2 8.67 7) 1-2 8.1 8) 1-2 7.8 9) 1-2 8.0 10) 1-2 7.9
1-3 .3 1-3 .3 1-3 .3 1-3 .3 1-3 .3
1-4 8.01 1-4 8.5 1-4 7.8 1-4 8.2 1-4 8.0
2-3 8.4 2-3 7.9 2-3 8.5 2-3 7.6 2-3 8.0
2-4 .4 2-4 .4 2-4 .4 2-4 .4 2-4 .4
3-4 8.15 3-4 8.1 3-4 8.1 3-4 8.5 3-4 7.9
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Re: Apex LD 4088 backlight shut down
Can you recheck some of your readings and were they ohms, Kohms or Megohms?
The transformers usually have a minimum of two windings on them so if one set of windings were labelled 1 and 2 and the other winding was 3 and 4 then you would expect a resistance reading of eg ohms for one set of windings and maybe 10's if not 100's of ohm for the second set of windingsLast edited by dick_barton; 10-03-2020, 04:21 AM.Willing to help but I'm no expert.
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Re: Apex LD 4088 backlight shut down
I'll assume that Pins 1 - 3 where it changes half way down is a typo.
The ony odd reading is T4, Pins 1 -3 @ 0.02 which could be an error in the reading but worth rechecking.
Can you also recheck Pins 2- 4 of each transformer with your meter set to ohms and post back the results.Willing to help but I'm no expert.
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Re: Apex LD 4088 backlight shut down
Originally posted by dick_barton View PostI'll assume that Pins 1 - 3 where it changes half way down is a typo.
The ony odd reading is T4, Pins 1 -3 @ 0.02 which could be an error in the reading but worth rechecking.
Can you also recheck Pins 2- 4 of each transformer with your meter set to ohms and post back the results.
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