Sceptre 409BV-FHDU8HJ1L02 dead

[bigmatt0211]

Hello all, my Sceptre cut out on me :/. I don't get anything. No lights, power, nada. I'm fairly competent with electronics, but have no idea where to start with TVs. Anyone willing to help me get this thing back up and going? I'd lvoe the opportunity to learn about it. I've attached the pictures of the two boards.

[brucetv]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

Take your DMM and provide us with the voltage readings at CN5/6 and others. Also check voltage at main filter cap. Check all fuses and esr's on the 6 caps on the power supply and let us know what you find.

[bigmatt0211]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

So, looking at my DMM, I realize I don't have capacitance measurements. Will that be a problem?

I don't seem to get any voltage on cn5/6 or any other of the wires leading off the board. I tested them with a wire poking each one (while the connecter was still on it). The voltage across the main cap is 166.5v. I will get the other caps in the morning.

Thank you for your help so far!

[bigmatt0211]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

So, I am having a hard time getting any measure on those other caps. It seems they are sitting at 0. Maybe C62 - the little black one on top, maybe is 3.7 mV. The main cap also seemed to drop the longer it's plugged in.

[dick_barton]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

With the power supply disconnected from the mainboard what voltages do you have at the connectors.

[bigmatt0211]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

Ok, after disconnecting the power and letting it sit overnight, I measured the voltages across each of those connectors. The only one that had anything was the NC connector which ranged around 2.5mV - 13.3 mV. All of the others were 0.

[dick_barton]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

Using your meter set to dc volts can you carefully measure the voltage between the two legs of capacitor C64.

It's on the live side of the mains supply so be careful taking the measurement.

[bigmatt0211]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

So, right now I am getting nothing. I measured with two different DMM. When I measured it earlier in this post, I had 166.5V.

So partial side story, when I was getting the measurements, I had the power board on its side. I guess I pushed it a bit too much, and something grounded with the back of the tv (i think). There was a spark and the fuse to the room popped.

[dick_barton]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

Pity since all the measurements could have been done from the top of the board with it still in place.

[bigmatt0211]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

Yeah, true. I was checking for solder issues and measuring some of the other caps. So, what are your thoughts?

[slickrickybobby89]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

If you shorted the board there are more than likely more blown component's than what you were originally dealing with, i would suggest replacing that board completely with a replacement from shopjimmy.com or ebay, depending on availability, but you may also want to consider a new set, as there is a possibility that when you grounded the live board you may have damaged something else other than the power supply. And replacing multiple boards can get costly.

[slickrickybobby89]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

I recently repaired this same exact power supply and my issue was blown mosfets, check the pins @ q12 q11 & q6, look for a short between the 3 pins at each location.

[bigmatt0211]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

Ok, so, I replaced the power supply. Success... sort of..

It worked for a night just fine. I thought I was in the clear, but the next day, we were watching it and the screen turned off, though we still had sound. I unplugged it, plugged it back in and had image again. However, after we turned it off that night, it hasn't given me an image back. I still have sound, but the screen wont turn on.

Think you could help me troubleshoot this?

[cliff_hootarski]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

With the TV "On", shine a bright flashlight onto the screen and see if there is a faint image displayed on the screen.

[bigmatt0211]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

There was nothing that I could see.

[bigmatt0211]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

Any other ideas?

[CapLeaker]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

I think you have to explain much better what your issue is. No image... what do you mean? Are the backlights out? With everything plugged in and TV running, check the BLon and adj pin on the PSU.

When you turn the TV on, do the backlights come on for a second and then shut off? Do that in a dark room, or look into the vents on the back of the TV.
What does the LED indicator on front of the TV do?

In other words, you either got a main board problem (EEPROM) or a backlight inverter problem. For shits and giggles, freeze the EEPROM on the mainboard with a can of air upside down and turn the TV on. I think I gave you enough for now on your "To Do List".

[bigmatt0211]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

Cool, thanks. I will do that tonight. Just a little more background - The tv had sound, but no image. I checked with a flashlight, but didn't see anything. The front led does change from red to blue when I press the power on.

I'll let you know the results of that stuff tonight.

[bigmatt0211]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

Hey good news I think. I believe it is the backlight now. I was able to see the Sceptre logo on startup when I had a light on the screen.

[CapLeaker]

Re: Sceptre 409BV-FHDU8HJ1L02 dead

now you measure the DC V on the BLon pin.