Sceptre X405BV-FHD3HF02205 no power

[dnixon]

My sceptre lcd tv picture picture failed recently. The red light on the front doesn't come on and I understand from the troubleshooting guides that something in the power path has failed. I found an old thread on this tv that I will go through in detail, but I wanted to post a picture that shows some suspicious looking caps first and get an opinion. I don't have a setting on my phone camera that matches the max resolution so I picked something that was closest. I hope that is ok and appreciate any help. The caps in question are 4 on the right side of the picture ( the board is actually show upside down). The tops are grey instead of metallic silver, so I wonder if they are bad. I'd also appreciate info on where to find board schematics and other technical info for the tv.

[budm]

Re: Sceptre X405BV-FHD3HF02205 no power

Are talking about the parts with LA1, LA2, LA3, and LA4 designators? Those are inductors for the output filter for the Class D power amplifiers outputs.
Please up load the pictures of the whole back side of the TV so we can see all the boards.

[dnixon]

Re: Sceptre X405BV-FHD3HF02205 no power

OK. Attached is a picture of the whole back and one of the other main board

[dcapper]

Re: Sceptre X405BV-FHD3HF02205 no power

On the top left of the board, there is a part listed as F1. That's the fuse. Meter that and see if it's not blown. If it is, there could be more wrong with the power supply but let's start with that.

[dnixon]

Re: Sceptre X405BV-FHD3HF02205 no power

OK. I think the fuse is good. I get 0 ohms on the dmm. That was after a few seconds of fluctuating readings.

[budm]

Re: Sceptre X405BV-FHD3HF02205 no power

OK. I think the fuse is good. I get 0 ohms on the dmm. That was after a few seconds of fluctuating readings.

We need to find out of you do have about 150~160VDC betweeen the two legs of the main filter cap (the big cap laying on its side).
You must be real careful since you will be working in the HOT DEADLY side of the circuit.
Sceptre KW-PIV400102A Power Supply Backlight Inverter

http://www.shopjimmy.com/sceptre-kw-...-inverter.htm#

[dnixon]

Re: Sceptre X405BV-FHD3HF02205 no power

OK. I.m not experienced at this and have a couple of questions. To test the fuse I removed the shrinkwrap not knowing I needed to flip the board over. woiuldn't think so, but does that shrinkwap need to be replaced? Next, when checking the voltage on the cap will polarity matter connecting the meter? Any safety tips other than don't touch anything with bare hands?

[dcapper]

Re: Sceptre X405BV-FHD3HF02205 no power

The shrink wrap doesn't have to go back on. Don't worry about that. Like budm said be very careful when the tv is on. The power board can pack a punch. And make sure you don't short out anything while metering.

[dnixon]

Re: Sceptre X405BV-FHD3HF02205 no power

I have about 170 vdc on the cap

[budm]

Re: Sceptre X405BV-FHD3HF02205 no power

I have about 170 vdc on the cap

OK, good, now we need to find out if this Voltage is fed all the way to the STBY SMPS section or not, I will need to trace the connection from the + leg of the main filter cap and see if there is a fuse or fusible resistor on the way to the pin of the STBY power transformer or not, that is why I NEED to know if your board is an exact match as in post #6.

[dnixon]

Re: Sceptre X405BV-FHD3HF02205 no power

I have attached another picture of the front of the board and added one of the back. I thought that might be easier than trying to tell if my board is exactly the same as the post #6 picture. If this won't work i'll try to compare the board with the pictures. Also, I see that the size shown in the post for the pictures is much smaller than what I see on my hd. So I assume they are compressed wen uploaded. Does this mean I could attach a higher resolution picture?

[budm]

Re: Sceptre X405BV-FHD3HF02205 no power

OK, it is the same board.
You need to do resistance test on the Diodes D10, D21 (mounted on the heatsink), D22, and D23 to see if any of them show low resistance in both directions.

[dnixon]

Re: Sceptre X405BV-FHD3HF02205 no power

I tested the diodes 3 ways:

1) DMM in diode test mode

D10 - Forward 0v Backward 0v

D22 - Forward 0.16v Backward 0.9v

D23 - Forward 0.16v Backward 0.9v

D22 - This is a 3 terminal diode. I am calling the terminals 1, 2, and 3
where 2 is the middle terminal. I am assuming 2 is a common negative.

1,2 Forward .22v Backward first showed 0.9 then went to 0
3,2 Forward .22 v Backward first showed 0.9 then went to 0

1) DMM in ohms

D10 - Forward 0 Backward 0

D22 - Forward 0.86 Backward varies

D23 - Forward 0.88 Backward varies

D22 -

1,2 Forward 1.5k Backward 0
3,2 Forward 1.5k Backward varies

1) analog in ohmsx1

D10 - Forward 6 Backward 6

D22 - Forward 140 Backward 10

D23 - Forward 140 Backward 10

D22 -

1,2 Forward 500 Backward 10
3,2 Forward 500 Backward 10

[vinceroger69]

Re: Sceptre X405BV-FHD3HF02205 no power

D10 looks like it might be shorted you may have to remove it and re test

[budm]

Re: Sceptre X405BV-FHD3HF02205 no power

d10 looks like it might be shorted you may have to remove it and re test

+1

[dnixon]

Re: Sceptre X405BV-FHD3HF02205 no power

Removed D10 and retested:

DMM diode test - 0v forward and back
DMM ohms - 0 ohms forward and back

[vinceroger69]

Re: Sceptre X405BV-FHD3HF02205 no power

yes thats bad so you will need to obtain a new one. budm mayhave some more tests you can do just to rule out any more blown parts so wait for now until budm sees this post and then you can order the parts you need etc.

[budm]

Re: Sceptre X405BV-FHD3HF02205 no power

Removed D10 and retested:

DMM diode test - 0v forward and back
DMM ohms - 0 ohms forward and back

OK, you can leave D10 out for now, you can then apply an AC to the power supply board by itself without other boards connected, you should then see 5V at +5VSB pin of the connector CON 2.

[dnixon]

Re: Sceptre X405BV-FHD3HF02205 no power

5.25 vdc on +5vsb pin

[budm]

Re: Sceptre X405BV-FHD3HF02205 no power

You are good then, just replace that shorted out diode.