samsung LE40B551A6W black screen with sound

[andrewblueboy]

Re: samsung LE40B551A6W black screen with sound

ok pin 23 4.107 ON
0000 OFF

pin 25 EPWN 0.786 OFF
OL ON

pin 27 5v 0.707 OFF
OL ON

[andrewblueboy]

Re: samsung LE40B551A6W black screen with sound

It's the dc voltages at the pin 23 & 25 being asked for. With the black lead on the chassis and red meter lead on Pin 23 (Inverter On/Off), power on the set and give the voltage the meter reads. Repeat for pin 25 (Det_5V)

With the set off and using your meter set to ohms do all the "A" connect together and all the "B"

you say measure in ohms A connecto together and B together.
ive seen the A and B ost you have put on pic do you want the measure beteen the two post on each of the transfmores with tv off . have got this right

[dick_barton]

Re: samsung LE40B551A6W black screen with sound

Pin 23 Inverter On/ Off 4.17V, so the inverter is switched on
Pin 25 Det_5V = 5V, There is an inverter or lamp error. I would think a lamp error.

Resistance (ohms) is always measured with the power off.

[andrewblueboy]

Re: samsung LE40B551A6W black screen with sound

the A post 0.2 then drop to 0.1

B post 0.2 then drop to 0.1 aswell

ive had the tv apart again bulbs seem ok

[dick_barton]

Re: samsung LE40B551A6W black screen with sound

the A post 0.2 then drop to 0.1

B post 0.2 then drop to 0.1 aswell

ive had the tv apart again bulbs seem ok

Can you explain the comment "bulbs seem oK"

[andrewblueboy]

Re: samsung LE40B551A6W black screen with sound

Can you explain the comment "bulbs seem oK"

I have a lcd bulb tester which I connect to both sides or the bulb to light up . I use it to test laptop screen working aswell
Or is there a away I should be using a muti meter to test

Thankyou

[nomoresonys]

Re: samsung LE40B551A6W black screen with sound

Pin 23 Inverter On/ Off 4.17V, so the inverter is switched on
Pin 25 Det_5V = 5V, There is an inverter or lamp error. I would think a lamp error.

Resistance (ohms) is always measured with the power off.

Bud said "Det_5V is normally HIGH (it is active low, LOW = PROBLEM in backlights circuit)." So does 5v on pin 25 mean inv. or lamp error or does low equal problem? low is less than 5v correct?

[dick_barton]

Re: samsung LE40B551A6W black screen with sound

Have you soldered all the pins of each of the transformer as suggested in an earlier post.

[dick_barton]

Re: samsung LE40B551A6W black screen with sound

Bud said "Det_5V is normally HIGH (it is active low, LOW = PROBLEM in backlights circuit)." So does 5v on pin 25 mean inv. or lamp error or does low equal problem? low is less than 5v correct?

If the BD9893 drive IC stops either due to being faulty, or an error being returned from the Inverter circuit via OVP then it disables the inverter IC.
When the IC stops then DET_5V error occurs and is pulled low ie 0V

The video pointed to in an earlier thread showed a way to overcome the protection to check if there were any tubes failing to light.

[andrewblueboy]

Re: samsung LE40B551A6W black screen with sound

Have you soldered all the pins of each of the transformer as suggested in an earlier post.

Yes heated up pins and added it bit of fresh solder. It's becoming a bit of a task trying to sort it. I'm pleased I'm getting advice on this

[andrewblueboy]

Re: samsung LE40B551A6W black screen with sound

If the BD9893 drive IC stops either due to being faulty, or an error being returned from the Inverter circuit via OVP then it disables the inverter IC.

The video pointed to in an earlier thread showed a way to overcome the protection.

This video of the protection would it be worth me trying this and see what happens or could I be asking for more trouble as I'm only a learner at this

[dick_barton]

Re: samsung LE40B551A6W black screen with sound

There's no reason why you should be asking for trouble. The component he lifted is a small surface mount 0 ohm resistor (used as a link) so you need to be careful not to lose it, reference JR860
If the tubes do not light up then the problem is elsewhere.
Watch the video and take your time and don't rush it.

[nomoresonys]

Re: samsung LE40B551A6W black screen with sound

Can also check youtube, there's some good videos on transformer testing.

[andrewblueboy]

Re: samsung LE40B551A6W black screen with sound

There's no reason why you should be asking for trouble. The component he lifted is a small surface mount 0 ohm resistor (used as a link) so you need to be careful not to lose it, reference JR860
If the tubes do not light up then the problem is elsewhere.
Watch the video and take your time and don't rush it.

hi there well progress so far. ive gone over my solder joints on the transformer again and also lifeted the JR860. now the tv is ON. no dark areas as if a tube is out, so what do it do now then do i leave it or reconnect the JR860

[dick_barton]

Re: samsung LE40B551A6W black screen with sound

It's not advisable to run anything with the protection circuits disconnected otherwise there would be no need for them.
Can you post a nice sharp and well focused picture of the underside of the board so that the component references can be read.

[andrewblueboy]

Re: samsung LE40B551A6W black screen with sound

It's not advisable to run anything with the protection circuits disconnected otherwise there would be no need for them.
Can you post a nice sharp and well focused picture of the underside of the board so that the component references can be read.

here are some

[andrewblueboy]

Re: samsung LE40B551A6W black screen with sound

here some more

[dick_barton]

Re: samsung LE40B551A6W black screen with sound

Can you replace the jumper JR860.

I can't think of a simple way to isolate the fault other than knowing that there is an error being generated by the lamp circuitry.

If you feel confident then there are a number of diodes DI8106 to DI812.
Can you carefully lift pin 3 of DI806 and switch on. Do the backlights stay on?
If not reconnect pin 3 and move on to DI807 and switch on. Do they stay on.
If not reconnect pin 3 and move to the next diode..
Repeat until the backlights stay on and report the diode number.


If anyone else can think of an easier way then I'd like to hear.