I have a very strange problem with a Samsung LN40A530P1F (LN40A530P1FXZA).
The problem: In the settings, the back light level can be adjusted from 0 to 10. 10 is the highest. As expected, the backlights get dimmer as the number is adjusted down. When going down from 5 to 4, the backlights go off. The lights stay off even when the backlight level is adjusted back up. They stay off until the power is cycled.
Also, when "Mode" is changed from "dynamic" to "standard", the backlights goes out.
There is a signal from the main board to the power supply/inverter board called PWR_DIM. I measured the voltage of PWR_DIM at different backlight levels:
Level - Voltage
10 - 4.74
9 - 4.55
8 - 4.42
7 - 4.11
6 - 3.73
5 - 3.21
4 - 0.80
3 - 0.48
2 - 0.26
1 - 0.12
0 - 0.09
There is a big voltage change between level 5 and 4, where the lights go off.
I assume the voltage from the inverter to the backlights gets too low to keep the CCFLs on. Once the CCFLs go off, they stay off. They will not restart until the power is cycled.
I assume the main board is putting out an incorrect voltage on the PWR_DIM line. Possibly a Digital to Analog error.
The main board is Pearl BN41-00975C (BN96-08758B). There are a few for sale on eBay. Around $100. It would be great if I could get this down to a component level. I am not even sure the main board is defective.
Some history: I acquired this TV from a local e-cycle place. It had a color problem that I fixed with a new T-Con board. I stumbled across this second problem when adjusting the TV. I have checked the P/S board with an ESR meter. I did not any bad caps.
I could live with the problem, since I know never to adjust backlight level or change mode from "dynamic" to "standard". But I would like to sell this. I can not sell it with this problem.
Questions:
Has anybody seen this problem?
Is there a fix?
Short of buying another main board, What else should I do to trouble shoot?
Suggestions?
The problem: In the settings, the back light level can be adjusted from 0 to 10. 10 is the highest. As expected, the backlights get dimmer as the number is adjusted down. When going down from 5 to 4, the backlights go off. The lights stay off even when the backlight level is adjusted back up. They stay off until the power is cycled.
Also, when "Mode" is changed from "dynamic" to "standard", the backlights goes out.
There is a signal from the main board to the power supply/inverter board called PWR_DIM. I measured the voltage of PWR_DIM at different backlight levels:
Level - Voltage
10 - 4.74
9 - 4.55
8 - 4.42
7 - 4.11
6 - 3.73
5 - 3.21
4 - 0.80
3 - 0.48
2 - 0.26
1 - 0.12
0 - 0.09
There is a big voltage change between level 5 and 4, where the lights go off.
I assume the voltage from the inverter to the backlights gets too low to keep the CCFLs on. Once the CCFLs go off, they stay off. They will not restart until the power is cycled.
I assume the main board is putting out an incorrect voltage on the PWR_DIM line. Possibly a Digital to Analog error.
The main board is Pearl BN41-00975C (BN96-08758B). There are a few for sale on eBay. Around $100. It would be great if I could get this down to a component level. I am not even sure the main board is defective.
Some history: I acquired this TV from a local e-cycle place. It had a color problem that I fixed with a new T-Con board. I stumbled across this second problem when adjusting the TV. I have checked the P/S board with an ESR meter. I did not any bad caps.
I could live with the problem, since I know never to adjust backlight level or change mode from "dynamic" to "standard". But I would like to sell this. I can not sell it with this problem.
Questions:
Has anybody seen this problem?
Is there a fix?
Short of buying another main board, What else should I do to trouble shoot?
Suggestions?
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