Seiki SE421TT,Powers on and off. No picture, no backlights.

[johnboy1313]

Shopjimmy sells the EEPROM and a kit for the PSU. At power on, the LED on the front lights up blue. The main cap comes up to 392V and most of the pins on the main connector of the PSU go high to 5V, but there is no power at the connectors for the LEDs and no power at the fuse on the T-Con. At power off, the blue LED shuts off, most of the 5V pins drop to zero, and the main cap drops to 160V. I'm not sure if the problem is the PSU or the main. Any thoughts?

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

Psu

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

T-Con

[ERICSSON89]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

firstly, look like ur mainboard is not sending the 5v/12v supply to TCON board or the fuse in the TCON are blow and secondly, the PSU inverter circuit is fail to delivery the voltage to LED which makes the set to shut down.

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

The set never shuts down. It tirks on and off with the power button. There are no inverters, it's LED.

[zorro871]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

Have you check the volts coming out of the power board see if you have the 12 volts and 5 volts going to the main board but first unplug the led lights from the power board first. Then check the voltage if checks out then you have a short in one of the led lights

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

I've done all of that. No 12V at all, no power at the LED connectors.

[budm]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

At this point it looks like you do have PS_ON because the PFC Voltage booster did kick in and get the boosted voltage on the main cap but the T1 transformer smps which produces the 12V and the Voltage for the LED backlights is not working.
SJ has a repair service for this board so it must be common failure.
http://www.shopjimmy.com/catalogsear...=HTX-PI420402A

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

I found this while digging around this afternoon. It gives me a starting point anyway. I don't see any mention of the missing12V though.

[budm]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

It looks like PART3 will be the one in you case since you do have standby and boosted Voltages.
SJ does not have the pictures of the bottom side of the board, can you upload your pictures?

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

So QF5 is failed open both ways in diode mode and QF10 is shorted both ways in diode mode. They are both the same part number. ICF1 and ICF2 are both the same, TL4948. It looks like they're LED drivers but I can't find a data sheet.

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

QF5 and QF10

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

Back of PSU, LED section

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

Continued, I'm on my phone and it will only let me attach one pic at a time.

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

Someone's been here before me.

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

Last pic

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

Oops. I missed one.

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

Replaced QF5, QF10, ICF1, and ICF2. All is good. Thanks to member freakaftr8 for getting me the part numbers for the LED driver ICs from the Shopjimmy kit.

QF5 and QF10 were replaced with FDD5353
ICF1 and ICF2 were replaced with TL494CD
All parts sourced from eBay.

ICF1 and ICF2 were both glued down to the board once all of the pins were lifted. A trace was damaged lifting IC1 from the board.

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

Looks like I spoke too soon. The set works but one side of the screen is considerably darker than the other. This set is a POS. I am done with low cost LEDs.

[johnboy1313]

Re: Seiki SE421TT,Powers on and off. No picture, no backlights.

One of four LED strips lighting.