Samsung LN46c650l1fxza no blacklight

[evilhero]

Hi, I have this problem with this tv. It will power up with 5 red led blinks. It will plays the samsung chiming sound but no picture or light. I can power it back down and it will played the chiming off. The model of powersupply is bn44-00341b, mainboard: BN41-01436b, inveter: t871070.00 I check the power while the power is ON.
CN802:
Pin1 B13v: 12.85v
Pin2 Lamp_det: 0v (jump to 3v than go down to 0v)
Pin3 B13v: 12.85v
pin4 sw_inv: 5.10v
pin5 b13v: 12.84v
pin6 pwm_dim: 0.84v
pin7 ground: 0v
pin8 h_sync: 1.73
Pin9 ground: 0v
pin10 ground: 0v
Pin11 b5v: 5.11v
pin 12 ground: 0v
pin 13 b5v: 5.11v
pin 14 b5v: 5.11v
pin 15 13/18vs: 12.85v
pin 16 A5v: 5.11v
pin 17 13/18vs: 12.86v
pin 18 power on/off: 0.87

CNI802:
Pin 1 12v: 12.78
Pin 2 fb: 0v
pin 3 fb: 0v
pin 4 gnd: 0v
pin 5 gnd: 0v
pin 6 LD: 9v
pin 7 LD: 9v

CNI801:
checked 0v ac
The cap seem to be okie no budge on the psu.

[tom66]

Re: Samsung LN46c650l1fxza no blacklight

There are one or two large 450V capacitors on the power supply. With a volt meter on the highest DC range check the voltage across them.

[tom66]

Re: Samsung LN46c650l1fxza no blacklight

Schematic for power board

[evilhero]

Re: Samsung LN46c650l1fxza no blacklight

The reading on both cap is 382v.

[budm]

Re: Samsung LN46c650l1fxza no blacklight

Any pictures of the boards? The PS_ON and the PFC Voltage booster is working OK otherwise you will not have the 380VDC on the main filter caps.

[evilhero]

Re: Samsung LN46c650l1fxza no blacklight

I cannot really tell the black light never flash. Just hear the samsung starting up chiming. Already attempted looking for bad transformer by checking the secondary wind with an ohms meter. All of them are the same measurement resistance. The psu unit seem to be cranking out the right amount of voltage. Do you think it is the mainboard telling the inverter board to be on protection mode? Thank you very much for helping me! budm =)

[tom66]

Re: Samsung LN46c650l1fxza no blacklight

Can you check the line marked BL ON?
Consider JP852/JP854 jumper cut - can help solve flickering backlight but maybe also no backlight?

[evilhero]

Re: Samsung LN46c650l1fxza no blacklight

I cannot see any marking on the mainboard call BL ON. I did removed the jp852 jumper with the same result. I read an older post when you disconnect the mainboard. The psu and inverter board will turn on the blacklight because the bl on will be missing. Unfortunately that step also fail. I'll cut JP854 tomorrow. My problem is similar to this thread: https://www.badcaps.net/forum/showth...ighlight=bl_on

until the lao guy hijack to something else.

[tom66]

Re: Samsung LN46c650l1fxza no blacklight

On this it is SW INV.

[budm]

Re: Samsung LN46c650l1fxza no blacklight

"pin4 sw_inv: 5.10v" So the BL-ON (SW INV) signal is OK. Per digarm, there is a fuse (FS802S) for the B+ (PFC) for feeding the Inverter circuit, is it OK?
So this TV has the Balancer board?

[evilhero]

Re: Samsung LN46c650l1fxza no blacklight

The fuses FS802s tested good and sw_inv pin 3 on psu measure: 5.08v "poweroff standymode": got 0v. Also tested FS801s to be good.

[tom66]

Re: Samsung LN46c650l1fxza no blacklight

Check the voltage across the exposed terminals of C1842 (there may not be a component here but you should be able to probe across the holes.) A low voltage here indicates a shutdown due to under-voltage lockout.

[evilhero]

Re: Samsung LN46c650l1fxza no blacklight

The c1842 reading from a hot ground point read: 59v

[tom66]

Re: Samsung LN46c650l1fxza no blacklight

Please measure across the positive and negative terminals of C1842. Red probe one end, black on other end.

[evilhero]

Re: Samsung LN46c650l1fxza no blacklight

this c1842 is the mainboard or psu?

[evilhero]

Re: Samsung LN46c650l1fxza no blacklight

opsss.. was measuring c1802.. found the c1842 reading as 3.75v

[tom66]

Re: Samsung LN46c650l1fxza no blacklight

OK, that would appear to be OK.

With the black probe on the negative lead of the large 450V capacitor, what voltages do you measure on each end of the fuse FS802S?

[evilhero]

Re: Samsung LN46c650l1fxza no blacklight

yeah, I probe the fuse on both end check out to be 378v. what else do you want to check?

[evilhero]

Re: Samsung LN46c650l1fxza no blacklight

I took a picture of the powersupply and did some more testing on the inverter high AC side. all the transformer point test at 150-230 ac which is similar to cni801. I saw a video where u can jump the powersupply sw_pwr with another pin to get the lcd tv black light on without the mainboard. If so what is the pin do I short together pw_sw?

[budm]

Re: Samsung LN46c650l1fxza no blacklight

It has built-in pull-up resistor already, all you have to do is to disconnect CN802.