KDL-55NX720 Pwr Led Blinks 5 times

[fcisolutions]

From another post where this same Sony model was blinking 4 times I found this:
CoppellTVRepair wrote:

Haven't figured it out yet, partially because of Sony's idiotic design where if anything is disconnected (or failed) the whole TV shuts down ...

Looking up the 5 blink code says I have a bad panel. But what is frustrating is if I disconnect everything related to the panel and I still get the same 5 blinks.

Voltage readings:
1 - 3.25v - Power_ON ----------2 - 0v - NC
3 - 3.30v - PFC_ON ------------ 4 - 0v - NC
5 - 0v - NC ---------------------- 6 - 1.67v - BL_ERR
7 - 2.75v - AC_OFF_DET ------- 8 - 0v - T-CON_ON
9 - 0v - GND ------------------- 10 - 3.3v - STBY3.3V
11 - 0v - AU_GND ------------- 12 - 10.7v - AU_12V
13 - 0v - AU_GND ------------- 14 - 10.7v - AU_12V
15 - 0v - GND ----------------- 16 - 10.7v - REG_12V
17 - 0v - GND ----------------- 18 - 10.7v - REG_12V
19 - 0v - GND ----------------- 20 - 10.7v - BOR_ASU_12V
21 - 0v - GND ----------------- 22 - 10.7v - BOR_ASU_12V
23 - 0v - GND ----------------- 24 - 10.7v - TCON_VCC_12V
25 - 0v - GND ----------------- 26 - 10.7v - TCON_VCC_12V
27 - 0v - GND ----------------- 28 - 10.7v - TCON_VCC_12V

[dskall]

Re: KDL-55NX720 Pwr Led Blinks 5 times

If you unplug the 12v stuff do you still get 10.7v?

[fcisolutions]

Re: KDL-55NX720 Pwr Led Blinks 5 times

The main board has been isolated, forced power supply on, by jumpering standby to power_on and the 12V rail came to 12.75V.

[dskall]

Re: KDL-55NX720 Pwr Led Blinks 5 times

Possible bad cap on 12v supply. Probable short dragging down voltage

[fcisolutions]

Re: KDL-55NX720 Pwr Led Blinks 5 times

Possible bad cap on 12v supply. Probable short dragging down voltage

Are you thinking the bad cap is on the main? Remember the power supply puts out the right voltages when the main is disconnected/isolated. Do you think replacing the main board is our best bet?

[budm]

Re: KDL-55NX720 Pwr Led Blinks 5 times

You can try using 1A load on that 12V output to see if it can even handle 1A load to start with. The PFC Boosted Voltage also staying at around 380~400V range?

[fcisolutions]

Re: KDL-55NX720 Pwr Led Blinks 5 times

You can try using 1A load on that 12V output to see if it can even handle 1A load to start with. The PFC Boosted Voltage also staying at around 380~400V range?

To use a 1A load would I put a 12ohm resister from 12v to ground?

[fcisolutions]

Re: KDL-55NX720 Pwr Led Blinks 5 times

You can try using 1A load on that 12V output to see if it can even handle 1A load to start with. The PFC Boosted Voltage also staying at around 380~400V range?

And the PFC is 393v when I power the supply with a 1k resistor (eliminating the main).

[dick_barton]

Re: KDL-55NX720 Pwr Led Blinks 5 times

To use a 1A load would I put a 12ohm resister from 12v to ground?

12V, 12W car bulb would do the job

[budm]

Re: KDL-55NX720 Pwr Led Blinks 5 times

12V, 12W car bulb would do the job

The cold resistance of the lamp may trip the over current circuit, the cold resistance of the lamp can be about 15 times lower than the hot resistance.

[fcisolutions]

Re: KDL-55NX720 Pwr Led Blinks 5 times

You can try using 1A load on that 12V output to see if it can even handle 1A load to start with. The PFC Boosted Voltage also staying at around 380~400V range?

The power supply (w/o main connected) is forced on via 1k resistor to standby voltage and then I wired a 12v, 1.3amp fan from the 12v rail to gound. The voltage dropped from 12.75 to 12.44 with the fan running at full speed. PFC is stable at 392v during this test.

[dskall]

Re: KDL-55NX720 Pwr Led Blinks 5 times

I would start disconnecting 12v loads one at a time till voltage comes up

[fcisolutions]

Re: KDL-55NX720 Pwr Led Blinks 5 times

I would start disconnecting 12v loads one at a time till voltage comes up

With the main disconnected and everything else plugged up 12v is good. Going to try ordering a main board. Thanks for your help.

[fcisolutions]

Re: KDL-55NX720 Pwr Led Blinks 5 times

Main board arrived and the voltages stabilized. But still no picture. The problem is, isolating seems to trigger the led to blink 5 times. For example, I connected just the main and I get the 5 blinks. So how is a tech suppose to troubleshoot?

Also I don't get the LEDs to light. There is a LED driver brd responsible to send the BL-ON turn on voltage to the secondary power board. Thanks Sony.

[fcisolutions]

Re: KDL-55NX720 Pwr Led Blinks 5 times

I was able to test the leds and each string (there was 4) was pulling 30volts. So looks like leds are good.

[nuala]

Re: KDL-55NX720 Pwr Led Blinks 5 times

Service manual for 5 blinks is t-con error/panel ID NVM error. T-com control MT board.

[fcisolutions]

Re: KDL-55NX720 Pwr Led Blinks 5 times

Yes that's right. But remember, I get 5 blinks whether I have just the main board connected or main, led driver or main, led driver, tcon or main, led driver, tcon, and panel.