Sceptre X32 Power Supply Diagnosis

[Version 7]

I attempted my first TV repair and got close, but no cigar... and I'm not sure where to go next.

The unit is a Sceptre X32 LCD TV and originally would not power up at all. It had 4 CapXon capacitors, two leaking/bulged, so I replaced all 4 with nichicon HE equivalents. The rest of the capacitors look OK, but I do question the large blue capacitor (filter cap?) as it feels like it could be slightly bulged, but I'm unsure and I don't have a capacitance meter.

After the repair, the unit does power up and displays the logo, but after about 4 seconds, the unit powers downs completely. No output voltage from the power supply at all. The unit will also not power up again until it has been disconnected from the mains for about 30 seconds (the time it takes for the indicator light to go dead).



In the photo of the power supply:

Connector "A" goes to the control board. It has 3 5v, 2 12v, 2 24v and 3 ground leads.

Connector "B" goes to the inverter board. It has 5 24v and 5 ground leads.
There is also a 2 wire feed from the inverter board (on the same connector as from the power supply) to the control board on its own connector (red and orange).

Green dots are the caps I replaced.

When first connected to the mains, the indicator light starts blue then to red (normal - TV not on).

On connector "A", all voltages are correct for about 4 seconds then fall to 0v except for 1 5v lead that remains active. Also note; the other two 5v leads first drop to about 2.1v then slowly to 0v.

On connector "B" all voltages are steady and correct for about 4 seconds and then fall to 0v.

The two leads from the inverter board to the control board read 3.5v for the 4 seconds then falls to 0v.

When the unit is then powered on with the power button, all voltages come back to specs but after the back light has been on for about 4 seconds, all output voltage is lost.

I have also tested the unit with the inverter board disconnected at the power supply, but with the two leads from the inverter board to the control board still connected, with the same results.

I'm just not sure if this is the power supply failing or if the control board is issuing a power supply shutdown - or how to test.

Thank you all.
Kevin

[IamCanadian]

Re: Sceptre X32 Power Supply Diagnosis

Do you hear a click when it dies?

[Version 7]

Re: Sceptre X32 Power Supply Diagnosis

I do not. No clicking, buzzing, etc..

[budm]

Re: Sceptre X32 Power Supply Diagnosis

So the standby 5v also drop down?
Are there any labeling on the A and B connectors such as PS_ON, BL_ON, etc.
Can I see close up picture of these two connectors and the pictures of the whole TV so I can see how all the boards are connected together?
There are startup caps in the primary side that more likely should be replace. They are for PFC voltage booster, 5V standby, 12v/24v power supplies.
The 3.5v you see on the pins are for the BL_ON and PS_ON which are generated by the main board.
Need to see more pictures.
By the way, bad cap can look normal but can have high ESR or bad value. it is always best to replace them as a set using low ESR TYPE capacitors such as PANASONIC FM/FR series.

[Version 7]

Re: Sceptre X32 Power Supply Diagnosis

Connector "B" is well marked but connector "A" not so well. The right side shows the one ground at the top then the two 5v and two grounds at the bottom. The left side of the connector is actually marked "24v Audio" - I don't think that is right...

Here are the voltage readings I took on connector "A", from top to bottom.

Black ground
Brown 5v
EMPTY
Red 3.5v
Orange 12v
Yellow 12v
Green 24v
Blue 24v
Purple 5v
Gray 5v
White ground
Black ground

The brown 5v and the ground above it is the only circuit that retains its voltage after the unit is first plugged in. When the unit dies after being powered on, this circuit also drops to 0v.

I had read some of the forums before I started this repair and the panasonic caps seemed to be well recommended but I couldn't find any at the time that matched the physical size of the CapXon's. According to nichicon, their HE caps are "Extremely low impedance.... For use in switching power supplies". Wasn't sure just how important physical size was and these matched.

The startup caps you pointed out are OST caps - sounds like they may not be the greatest... would these still cause an issue once the power supply has started?

Thank You for your help
Kevin

[budm]

Re: Sceptre X32 Power Supply Diagnosis

"Red 3.5v" that is more likely to be PS_ON. When TV is off, this should go down to 0 which will also causes the 12v and 24v to shutdown (TV will be in standby mode).

The brown 5v and the ground above it is the only circuit that retains its voltage after the unit is first plugged in. When the unit dies after being powered on, this circuit also drops to 0v.

"Purple 5v
Gray 5v" How about these two 5V, do they also drop to 0V also?
Can I get good shot of the bottom side as a whole and also in 1/4 section so I can see the traces?
If the start up caps are bad, when it has heavy load like when the TV is on, the power supply may go into shutdown.
One thing I notice is that the top connector of the power supply has all the wires on it, but the other end that connects to the right side of the main board does not look like it has all the wires, may be the picture is not clear enough for me to see.

[Version 7]

Re: Sceptre X32 Power Supply Diagnosis

The grey and purple 5v do drop off as well, but differently than the other voltages. When the unit is first plugged in, they are both 5v but after about 4 seconds, they drop down to 2.1 volts then very slowly (minute or more) discharge to 0v while the 12v and 24v circuits drop to 0v within a few seconds. After the unit is powered on and about 4 seconds after the logo appears, all voltages drop to 0v within a few seconds.

For the feed from the power supply to the control board they used a 12 pin connector at the power supply and a 15 pin connector at the control board so the power supply connector has one empty space and the control board has four empty spaces.

Thanks for taking a look at this for me

Kevin

[budm]

Re: Sceptre X32 Power Supply Diagnosis

That means the 5v standby power supply is not working properly. I would reaplace those start up caps I redlined and see what will happen next.

[Version 7]

Re: Sceptre X32 Power Supply Diagnosis

ok I'll give it a try - will have to order, so be back in a few days..

[Version 7]

FIXED - Sceptre X32 Power Supply Diagnosis

Thank You budm for your advice - replaced startup caps and this set has been up and running for a few weeks now!

[budm]

Re: Sceptre X32 Power Supply Diagnosis

Thank you for the repair feedback.

[tom66]

Re: Sceptre X32 Power Supply Diagnosis

Another set saved from the trash, well done.

[macwalnut]

Re: Sceptre X32 Power Supply Diagnosis

I have a sceptre x32, I get a picture and sound for about a second or two then both go out, the blue light stays on. If I power it down and back up it will do the same thing. Visually all caps look good.

[budm]

Re: Sceptre X32 Power Supply Diagnosis

Bad cap can look normal.
How about the voltage readings on the connectors and the pictures of YOUR boards?

[buckeye492]

Re: Sceptre X32 Power Supply Diagnosis

Figured I would add on rather than starting a new post. I too have the X32 TV & it suddenly wont turn on. I have the blue light after hitting the power button, but no picture & no clicking sounds, etc. It has the AY118P-4HF01 power supply. I don't see any obviously bulging capacitors. After checking the voltages, I have 0 vdc on all pins with the power cord in, but not turned on. After hitting the power button, I have +5, +12 & +24 vdc on all the pins marked as such. Sounds like a startup problem in the power supply, but it has been a number of years since I have worked on a TV, so I could be completely off base. Back when I did this for a living, we could "jump" the suspected bad cap with a known good one. Not sure if this is an option with newer TV's or not. Thanks for any insight.

[Schszbrgr4782]

Re: Sceptre X32 Power Supply Diagnosis

Have you found your problem I currently have the same issue with my set!

[buckeye492]

Re: Sceptre X32 Power Supply Diagnosis

I have not. I replaced the power supply board. All the voltages seem to be working correctly, so I assume the problem lies elsewhere. I am just not really sure where to start at this point.

[budm]

Re: Sceptre X32 Power Supply Diagnosis

So you get all the correct voltages to run the inverter? How about the BL_ON and Dimming signals from the main board?

[budm]

Re: Sceptre X32 Power Supply Diagnosis

Have you found your problem I currently have the same issue with my set!

Same problem as the original OP?

[tzantzai]

Re: Sceptre X32 Power Supply Diagnosis

Hi all. I have Scepter X32 LCD TV that cannot power up. When I press the power knob the pwr LED turns blue but the screen is dark and no sound. Occasionally after 5, 6 power cord disconnects and reties it will power up normally. I measured the voltages on power supply board after power up: 24VDC = 22.6V, 12VDC = 12.4V, 5VDC = 5.3V. When the TV powers up OK: BL_ON = 5.0V. When the TV cannot power up BL_ON = 0V. Any ideas what’s wrong? Thanks.