Sceptre X505BV-FMDR

[budm]

Re: Sceptre X505BV-FMDR

That is the connector of the LED string.
What is the DCV rating of C8F, 9F?

Sceptre AY160D-4HF06 Power Supply for X505BV-FMDR
http://www.shopjimmy.com/sceptre-ay1...pply-unit.htm#
Pictures provided by shopjimmy.

[nwcs]

Re: Sceptre X505BV-FMDR

I have same issue and have no voltage to leds at connector 10. All other voltages are fine. Same issue if I unplug the led connector. I would have to presume bad power supply.

[nwcs]

Re: Sceptre X505BV-FMDR

Tested the led's and found one open led. Put in 1w 3.3v zener and now up and working. I guess 0v at the led connector does not mean a bad power supply.

[Force2recwith]

Re: Sceptre X505BV-FMDR

I have the same tv, and having black screen with sound. Sorry if this question is ridiculous, but I'm not very tech savvy, would it be easier to purchase a new power supply, or try to replace the led bulbs as others have stated they have performed?

[budm]

Re: Sceptre X505BV-FMDR

You need to at least be able to check the Voltages, it may be power supply or LED problem.

[nwcs]

Re: Sceptre X505BV-FMDR

A good led tester would help. I found that the scepter tv's are deceptive and do not have any voltages or low voltages on the led inputs if there is a shorted led.

[Force2recwith]

Re: Sceptre X505BV-FMDR

Is the led bulb most commonly needing changed out found on the main board/power supply?

[budm]

Re: Sceptre X505BV-FMDR

Most common failure in the TV with LED backlights that no longer light up are due to bad LEDs, they drive them too hard so they failed like crazy.
The backlights level should be set to 75% or less from the maximum setting.
Replacing the LEDs are not the beginner either since you will have to take the LCD panel apart to get to the LEDs, that is why it is important to test the Voltages first.

[customer2042]

Re: Sceptre X505BV-FMDR

I have exactly same problem with the same Sceptre X50 TV as topicstarter reported on the first page. I found a bad LED in backlight strip and replaced it with 2835 LED as it was recommended in this thread. 100 LED's were found for $6 on eBay

I don't have low temperature soldering compound and used regular eutectic tin-lead 60/40 compound. Burned 3 LED's with practicing before learned a proper technique to solder them. 4th LED was successful and backlight was restored. I assembled TV back and it turned on as normal. However after about 3 minutes of running another random LED burned in backlight. I guess it will continue to burn if I keep replacing them.

Picture was not super-bright. But I didn't capture voltage when backlight was working. What should be normal voltage for backlight in this TV?

When backlight failed or disconnected, voltage jumps above 300V for a second after turning TV on and then drops down to zero. I believe it's normal (kind of protection of overvoltage) as mentioned by other participant of this thread.

Any ideas? What can be causing backlight LED's to burn so quickly?

[budm]

Re: Sceptre X505BV-FMDR

Its the current that you need to check, LED's are current device, it they run at close to the limit, which is typical in most TV with LED backlights, they will burn up fast. What is the current rating of the replacement LED?

[customer2042]

Re: Sceptre X505BV-FMDR

Its the current that you need to check, LED's are current device, it they run at close to the limit, which is typical in most TV with LED backlights, they will burn up fast. What is the current rating of the replacement LED?

20ma/3.4V front voltage max for replacement LED 2835

The problem is that random LED's burn in random BL strips, not a replacement LED

[budm]

Re: Sceptre X505BV-FMDR

No way 20mA rating will last, they drive those LEDs in 300 ~ 400mA that is why they are 1W LED. So are you sure that it is rated at 20mA? that is awful low for even small white LED.
You should also look at the bottom side of the LED strip to see any over heated sign on each original LED.

[customer2042]

Re: Sceptre X505BV-FMDR

No way 20mA rating will last, they drive those LEDs in 300 ~ 400mA that is why they are 1W LED. So are you sure that it is rated at 20mA? that is awful low for even small white LED.
You should also look at the bottom side of the LED strip to see any over heated sign on each original LED.

Seller due20150801 on eBay where I purchases 2835 LED posted 20ma. Perhaps that was just current used to measure front voltage, not max ampreage. Other dastasheets found in Google show 80ma, 120ma and 240ma as max value.

It looks like max current very depends of manufacturer and not sure what is max on mine.

Interesting, how BadGoo (the name of author in one of postings on this thread) used 2835 LED for such repair of similar TV and they didn't burn?

Since I still have 96 of them for 6 cent a piece, I have temptation to hook one up to lab PSU and slowly increase current until it's fried. However the problem they are so tiny that it's hard to handle them and hook them up for testing

[budm]

Re: Sceptre X505BV-FMDR

The Vf is measured @ 20mA If. I wish they will put full spec on the page or the P/N.

[customer2042]

Re: Sceptre X505BV-FMDR

The Vf is measured @ 20mA If. I wish they will put full spec on the page or the P/N.

That explains...

I just asked that seller on eBay if he can give me a full datasheet or tell maximum current for those LED. Will look forward for his response

BTW, what is normal backlight voltage for Sceptre x505?

I don't remember exactly how many LED total there. It looks something about 60. So counting 60x2.4V should be about 144V total, shouldn't it?

How 300V peak at starting inverter wouldn't kill them unless 300V is just idle voltage?

[budm]

Re: Sceptre X505BV-FMDR

@300mA which is typical driving current, the Vf will be around 3 ~ 3.2V, the spec sheet will show the Vf VS If graph.
The power supply for driving is the constant current power supply that will maintain constant current through the LEDs. The Voltage will vary to maintain constant current. The is Active element (MOSFET is typical) on the sink side of the LED string + the current sensing resistor for for feedback signal to the LED driver IC which sends PWM drive to the MOSFET.
Look at the graph on page 10.
If you get the P/N of the LED driver IC then you can look up the spec sheet and see the application notes circuit showing how the LEDs are driven.

[customer2042]

Re: Sceptre X505BV-FMDR

Its the current that you need to check, LED's are current device

Since inverter keeps constant current for BL, not constant voltage, I just shorted out failed LED. Missing one of 70 - it's 1.42% drop in overall brightness and voltage. Not a big deal. Since it's between other (good) LED, behind diffuser and about 2 inch from LCD panel, darker spot is almost invisible on screen. As I understand electricity, it shouldn't make other LED work harder as current through them stays the same unlike in Christmas lights with shorted bulb

However now I have a different problem. Screen has three vertical black stripes from the top to the bottom of it in random places. One about 3 inch wide, second about 2 inch and third about half inch. I guess I might accidentally damage LCD as it slightly wobbled in my hands when I disassembled TV to reach backlight. Is it fixable? If so, any ideas how?

[zape]

Re: Sceptre X505BV-FMDR

Hi guys, Thank you so much for your help.
To clarify, this is what I have: The red LED that should turn on when the TV is plugged to the wall is always off (there was a time weeks ago when I could make it come back ON by unplugging the TV for a few minutes but that's no longer the case) This is the same LED that should turn blue when I turn the TV ON, but that doesn't happen either (the TV does not turn on at all. Flashlight test also fails)

As far as voltage levels on the PS board:
+5V: 4.99V
+12V: 12.34V
+24V: 23.80V
PS/ON: 4.42V
+5VSB: 4.99V
ADJ: 4.92V
BL/ON: 0.06V (both with respect to DC GND and Chassis GND)

There's also a small connector, called connector 10 (see pic, red/black wires) that reads -0.66VDC (with respect to each other, NOT with respect to CH GND or DC GND

Having similar symptoms on a E485BV-FMQR
I wonder if this is EEPROM or CPU
CPU runs so hot so I burned my finger when touched it.

[ghcjr]

Re: Sceptre X505BV-FMDR

Does anyone have Schematics?

[ghcjr]

Re: Sceptre X505BV-FMDR

Can one of you describe the best way to get to the LEDs? Do I simply remove the screws around the parameter? Are there any other steps? I am fairly certain I have a blown LED.