40PFL5505D/F7 power cycles

[Pioneerx01]

I am working on Phillips 40PFL5505D/F7.

When you plug the TV in, the status LED blinks 12-14 times (I guess that is normal start-up sequence), then turns solid, black-lights come on, no picture, no sound at any time. The back-lights stay on for 4-5 seconds, then TV shuts down, status LED turns off, and TV immediately restarts with 12-14 LED blinks, and then precedes from the beginning over and over. Pressing the power button does not interrupt the sequence at any point. Yes the LED blinks vary from 12-14 blinks before the LED turns solid.

Power supply provides constant and uninterrupted 5.3V stand by voltage. PSON reads 3.5V at all times, but at the time when back-lights turn off and TV restarts itself. BL_ADJ2 and BL_SW show positive readings at the time the back-lights are on and they are off rest of the time.

I have disconnected the inverter and T-Con, but the sequence is the same. The T-Con fuse is OK, and it does receive 12V, but only at the time the back-lights are on. Looking at the screen in the dark, I see no discolorations of the light on the panel, so CCFLs are most likely OK.

Any thoughts?

[saddle_au]

Re: 40PFL5505D/F7 power cycles

Disconnect the IR and switch cable CN3004 as well, sometimes these can cause issues. This cable goes to the IR board and daisy chains to the switch board.

Check the voltages (and their purity) on the caps and regulators circled in red. IC4602 takes in 12v (pin 2) and switches it down to 1.2v, switcher and inductor is on pins 7/8. IC4604 takes in 12v (pin 2) and switches it down to 3v3, switcher is on pin 3. IC4601 takes in 12v (pin 2) switches on pin 3 and makes 2.7v. It feeds a couple of other regs, IC4603 and IC3603 both 1.8v regs.

Check the reset chip IC3103 on pin 4 to see if it toggles before the power off.

Slightly heat IC3102 to see if it makes a difference to the boot. Its the settings eeprom.

Get the schematic from http://www.electronica-pt.com/esquem...artdown/24955/

[Pioneerx01]

Re: 40PFL5505D/F7 power cycles

4602: 12V on pin2, but 0V on either pins 7 or 8
4604: 12V on pin2 and 3.3V on pin 3 that toggles to 0V during reset
4601: 12V on pin2 and 2.7V on pin 3 that toggles to 0V during reset
3103: I can't find this IC

Good idea bout disconnecting the IR, I did not think of that. Sadly, no change.
I did pre-heat the EEPROM and the SMD capacitors before with no change.

[saddle_au]

Re: 40PFL5505D/F7 power cycles

The Inductor L4602 attached to the switcher reg IC4602 should have 1.2 volts on it to feed the frame rate chip. One side should look like noise and the other 1.2v. As long as there's 12v it runs.

What you are describing could also be bad BGA connections, although I see that lots in LG, not as much in Philips.