Sony KDL-46bx450 no red light

[Gootch46]

Ok first of let me say Thanks for taking the time to even read this, But this tv has got me beffudled. I have no red light no action when I press the power button or the remote, No backlight in dark room, nuttin. I tried unhooking the ir sensor and turning on (easy and cheap fix tried first) heres how the power board tests out

t-con on =0
T-con = Vcc 12v=.15
NC
Dimmer = 3.21
BL on= .15
BL err= 1.63
Reg 12v = 12.5
Reg 12v = 12.5
Reg 12v gnd= 0
Reg 12v gnd= 0
Audio 12v gnd = 0
audio 12 v = 12.5
power on = 3.3
acc off det = 3.04
stby 3.3 = 3.3

And the other side of the power board going to the inverter on that plug I get these voltages
Unreg 24v = 25.1
Unreg 24v = 25.1
Unreg 24v = 25.1
Unreg 24v = 25.1
Unreg 24v = 25.1
Gnd = 0
Gnd = 0
Gnd = 0
Gnd = 0
Gnd = 0
BL error = 1.63
BL On = .16
NC
Dimmer = 3.2
I also have it tested where it plug going out of main board to ir board and keypad(channel up down ) board , let me know if you want these .

[budm]

Re: Sony KDL-46bx450 no red light

At this point the main board is not sending the T-CON ON signal or the BL-ON (Backlights ON) signal.
History of this TV?
I will need to do the research on the 'BL error = 1.63' to see if >1V = ERROR (not normal), <1V = normal or not.

[Gootch46]

Re: Sony KDL-46bx450 no red light

Thanks Budm TV was my uncles is about 5 years old used sparingly, he said maybe 40 hours on it, Basement tv for Packer games.
He went down on the morning of the game and red light was on but would not turn on with remote or pushbutton so he unplugged it for a couple of minutes then after replugging into his powerstrip he had No red light at all , and just unresponsive.
I bought a new power board because the big capacitor looked suspect but it tests out the same way and the main boards for this tv are scarce, found new for like $200. If you need other pics or readings let me know. Thanks

[budm]

Re: Sony KDL-46bx450 no red light

What I would try next is to heat up the main board with hair dryer for 2~3 minutes and then plug the TV into the outlet to see what happen.

[Gootch46]

Re: Sony KDL-46bx450 no red light

Yep tried it, I got nothing No red light no led light on the main board... nada Starting to think this main board is DEAD

[fzabkar]

Re: Sony KDL-46bx450 no red light

Service manual:


http://www.eserviceinfo.com/download...1&fileid=65203

[fzabkar]

Re: Sony KDL-46bx450 no red light

Can you provide a better photo of the bottom left corner of the main PCB? I can see at least 3 switchmode DC-DC converters and one linear regulator.

Can you also show us the IC at the top left corner of the tuner?

[Gootch46]

Re: Sony KDL-46bx450 no red light

Thanks Fzabkar see if these are good enough to make things out. Let me know if you need better photos or diffedrfent area. Thanks Gootch24

[fzabkar]

Re: Sony KDL-46bx450 no red light

Sorry, no good.

[Gootch46]

Re: Sony KDL-46bx450 no red light

Ok sorry had an afternoon job, see if these help, Thanks for your patience all

[Gootch46]

Re: Sony KDL-46bx450 no red light

Anyone??

[freakaftr8]

Re: Sony KDL-46bx450 no red light

I'm shooting towards mainboard failure. Had any lightning strikes in the area or power failure?

[fzabkar]

Re: Sony KDL-46bx450 no red light

Can you identify the markings on the chips?

[freakaftr8]

Re: Sony KDL-46bx450 no red light

What'd uo with that second pic? There seems to be an IC missing and is that a burn spot on the top?

[budm]

Re: Sony KDL-46bx450 no red light

http://www.shopjimmy.com/sony-kdl-46...repair-kit.htm

The ICs and some components are not installed on the board, they are not missing..

[freakaftr8]

Re: Sony KDL-46bx450 no red light

okay the way that picture looks it looks like an IC was deliberately removed from the board. Especially in the center of then IC where the Solder inlies it just looks weird

[Gootch46]

Re: Sony KDL-46bx450 no red light

Let me just start by saying "Thank You" this is a hobby and a very impatient uncle for a tv that has only 40-ish working hours on it LOL Anyway No chips were removed it more of what budm said. I have a picture with the chips marked by their numbers I will finish the other 2 chips later today. I did happen to find a replacement main board from ebay for $55 bucks from aa somewhat reputable company so will report back but would still like to find out the cause or solution for this if you all dont mind helping further. As far as the burn look on the one pic , is just a bad shadow on pic is all was just trying to show close up. Thanks again for all your help and suggestions, will keep you posted

[freakaftr8]

Re: Sony KDL-46bx450 no red light

I can see a bett picture of that ic now. You could have a defective eeprom on that board. Hopefully the new one gets you going

[budm]

Re: Sony KDL-46bx450 no red light

Here are the good clear pictures of the main boards (there are two versions) from SJ.
Pictures provided by SHOPJIMMY.

[fzabkar]

Re: Sony KDL-46bx450 no red light

The MediaTek MT5389 SoC is used in the Sharp LC32LE440U (very blurry schematics):

LC32LE440U_SM[1].pdf:
https://www.badcaps.net/forum/attach...9&d=1420063070

APL5920, ANPEC, 2A, Ultra Low Dropout (0.24V Typical) Linear Regulator, adjustable:



FR9808, fitipower, 21V, 4A, 500KHz Synchronous PWM-Buck DC/DC Converter:

https://cdn.badcaps-static.com/pdfs/...7e9f8f2295.pdf

According to the Sharp manual, the following voltages should be present on the main board when the SoC is in run mode:

3.3V standby
1.5V DDR SDRAM (could be 1.8V)
1.25V AV125
1.2V Vcore
3.3V AV33
5VSB

I would help more, but the OP still hasn't provided the requested information.