Samsung LN32D403E4D. Sound, No Backlight

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

I see. I tested the voltage on the inverter board and it would cycle from 0V to ~200mV. Is this normal or a sign that the inverter is not receiving enough voltage from the power supply?

[budm]

Re: Samsung LN32D403E4D. Sound, No Backlight

The inverter circuit is fed by that 391V to that fuse that check out fine, some how that inverter section is not running.

[selldoor]

Re: Samsung LN32D403E4D. Sound, No Backlight

I will have to do lots of circuit tracing using the pictures to see how they are connected using pictures from SJ:
http://www.shopjimmy.com/samsung-bn4...upply-unit.htm
It will be quite time consuming since we do not have the circuit diagram for this power supply board.

Does this help at all ( Its only a diagram for the SEM2106)

https://www.badcaps.net/forum/attach...7&d=1405181144

[selldoor]

Re: Samsung LN32D403E4D. Sound, No Backlight

@ikeoyou.
When you have 391vDC on the BIG cap can you carefully test the voltage on each side of the fuse - Black lead on neg leg of BIG cap probe each side of fuse with
red lead. Then do the same on the Diode to the right of the fuse and then to the
fat red cap at the end. All high voltage so care required.
I read on another post on a similar board the diode next to the fuse failed.

@andariego
Are you working on the same/similar board, if so perhaps you can chip in with any info you have?

[andariego]

Re: Samsung LN32D403E4D. Sound, No Backlight

@ikeoyou.
When you have 391vDC on the BIG cap can you carefully test the voltage on each side of the fuse - Black lead on neg leg of BIG cap probe each side of fuse with
red lead. Then do the same on the Diode to the right of the fuse and then to the
fat red cap at the end. All high voltage so care required.
I read on another post on a similar board the diode next to the fuse failed.

@andariego
Are you working on the same/similar board, if so perhaps you can chip in with any info you have?

I was working on a Samsung power supply BN44-00440B, and had the same problem. Fix by changing an IC "FAN7930B". I think that is different to that which Ikeoyu has.

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

On each side of the fuse is 392V.
On each side of diode is 392V.
Red cap climbs from 150mV to 200mV and drops and repeats.

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

I was working on a Samsung power supply BN44-00440B, and had the same problem. Fix by changing an IC "FAN7930B". I think that is different to that which Ikeoyu has.

how did you arrive at the conclusion that the ic was the culprit?

[andariego]

Re: Samsung LN32D403E4D. Sound, No Backlight

how did you arrive at the conclusion that the ic was the culprit?

to be honest I found the fix solution from another web
site

[budm]

Re: Samsung LN32D403E4D. Sound, No Backlight

FAN7930B is the PFC Controller IC:

But you do have 391VDC on the main filter cap so the IC is working.

[aaronwt6]

Re: Samsung LN32D403E4D. Sound, No Backlight

I've had two of these sets already with backlight problems (and they aren't very old). Both had one bad ccfl. I sacrificed one to fix the other. Both would flash for a seconds at startup before the inverter shut down. I wasted a ton of time on them before figuring it out. Just a thought.

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

thanks for the input fellas. I grew tired of trying to diagnose this half-working board and instead ordered a new power supply board from eBay for $28.
It arrived today and fixed the issue. TV now works fine. Now i must figure out what to do with this power supply as well as the inverter board i ordered.

[budm]

Re: Samsung LN32D403E4D. Sound, No Backlight

Thanks for the follow-up, can't be $28.