Sound and picture but no backlight

[budm]

Re: Sound and picture but no backlight

I can do that tomorrow. I got all the tools and goodies in my hobby shack outside the house. I'll do it and report back tomorrow. I really appreciate all the help. Resistor to center leg and to chassis right?

Yes, if you trace out the middle pin of that Transistor, you can see that goes directly to the LED connector where the White wire of the Cathode of the LED string is connected to.

[budm]

Re: Sound and picture but no backlight

Post #7 are low res.
So here are High res pix provided by shopjimmy: RCA RE46HQ1004 (RS126S-3T01) Power Supply for LED46C45RQ.

Notes: SJ pix shows black bumpers that block out the traces, OP provided the pix in post 358 with bumper removed around the LED connector as I requested.

[JCdes]

Re: Sound and picture but no backlight

I got the resistor, 100ohm .5%, I'll do the test as soon as I get home from work. The led pinout from left to right is bottom led strip to top left strip in that specific order on both - and + led connections. Can I do the test using q206 instead of q201? I can see better if the string reacts since it's the bottom one and has big openings that let me take a better look if it flashes. I could add a momentary on switch also if that's ok.

[budm]

Re: Sound and picture but no backlight

You can use any one of the LED - pin.

[JCdes]

Re: Sound and picture but no backlight

Sorry guys but I can't do the test today, still at work...

[JCdes]

Re: Sound and picture but no backlight

Merry christmas! Did the test but nothing happens. 10 seconds, led did not even flicker and resistor did not get hot.

[JCdes]

Re: Sound and picture but no backlight

I took a short video using the tester to light up the bottom led strip. This has nothing to do with the resistor test. Just a vid showing the voltage on the tester and led brightness.

https://drive.google.com/file/d/1T9l...dvSE4UwKrX5HzL

[JCdes]

Re: Sound and picture but no backlight

I took a chance and replaced EC201 and EC202 with brand new caps and nothing changed. Just in case I wrote down the Part#'s for Q220 is B649A, D6 is BYC10, Q215 is 18n20 and D200 is MBR10200F, D2 is MBR20150F.

While looking at D2 I noticed some kind of solder splatter on T1's cold side. Here's the pic. It might be nothing but just want to show you what I saw.

[JCdes]

Re: Sound and picture but no backlight

MBR10200 on D200 has continuity among the two external legs. I did not remove it just tested on board.

[budm]

Re: Sound and picture but no backlight

Q103, U102, T1 are part of the always on SMPS.

D2 is the rectifier for the always on 12V which is then fed to switched MOSFET Q2 to provide switched 12V output at the connector CON2 when PS-ON is present.

D1A//D1B are rectifier for the always on 5VSTBY, this 5v is fed to MOSFET Q1 to provide switched 5V output at the connector CON2 when PS-ON is present.

D6 is the rectifier for the always on 60V (filtered by EC11, 12) that is fed to the Boost converter (L201, Q215, D200, U200, EC201/202) that will produce about 100VDC when BL-ON is present.

L102, Q102, U101, D101 are for the PFC Booster Voltage which is also turns on when PS-ON is present.

At this point it looks like the Boost Voltage is not high enough, the LED string with the bypass resistor should have lit up for seconds.
So you should remove the D200 and check it in diode mode and in resistance mode in both directions but before doing that I need you to remove that 3-pin connector CON4, then put black probe on the chassis, red probe on any one of the LED + pin, with the TV turned off you should see about 60V, then turn on the TV and see how high the Voltage jumps up to.

[JCdes]

Re: Sound and picture but no backlight

Con4 unplugged check voltage on any +led while on stdby. Then check again with tv powered on and con4 unplugged still?

[JCdes]

Re: Sound and picture but no backlight

60.6v power off, 63.6v for a second when power on is pressed then back to 62v

[JCdes]

Re: Sound and picture but no backlight

Forgot to mention I had measured Q220 previously nothing unplugged... On stdby it has 60v, 0, 35v. Powered on 0.6, 0, 0.1

[budm]

Re: Sound and picture but no backlight

Con4 unplugged check voltage on any +led while on stdby. Then check again with tv powered on and con4 unplugged still?

Yes.

[budm]

Re: Sound and picture but no backlight

60.6v power off, 63.6v for a second when power on is pressed then back to 62v

That is with CON 4 not in place, correct?

[JCdes]

Re: Sound and picture but no backlight

Yes con4 unplugged

[Diah]

Re: Sound and picture but no backlight

you keep swimming at wrong direction... as you dont have the equipment to measure led in circuit currents.... put your DM 200.V DC red probe on any LED+ and test black probe on all LED- one by one when you turn on the set post your results each led -V No. --- this is -V currents boost circuit ( always i corrected this thought over this forum .. LED circuit / UNIT depending on current not Volts. ) so all yours parts replacement was just spending parts and time.

[budm]

Re: Sound and picture but no backlight

Yes con4 unplugged

So with the CON4 unplug, you get about 60V because the BL-ON will not be present, and with CON4 connected you get about 72V between LED+ as reported earlier, it should be close to 100V but it is not working correctly.
So what is the test result of the D200 Boost converter diode?

[JCdes]

Re: Sound and picture but no backlight

72 is a one second peak... I'll do the d200 test tomorrow since I'm off work ti'll tuesday.

[JCdes]

Re: Sound and picture but no backlight

Also I ordered some d669's, all caps and the driver just in case I might need them. They will take about a week, parts are very cheap so I just ordered almost everything on the cold side except the "transformer" since I can't find part number for it.