Philips 19pfl3505d/f7 - No Power - Voltages drop

[caphair]

When first plugged into the wall the standby light glows white for a few seconds, then goes out.

When the light is on all voltages are present, once the standby light goes off all the voltages drop to about half their values or more on some rails.

To get the light to come on again it has to be unplugged from the wall for a while, if directly unplugged and plugged back in the voltages stay low. Any thoughts?

[freakaftr8]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

Unplug mainboard and monitor standby pin on power supply, see if the drop happens still.

Could be a shorted output regulator on mainboard dragging the rails down

[caphair]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

Unplug mainboard and monitor standby pin on power supply, see if the drop happens still.

Could be a shorted output regulator on mainboard dragging the rails down

I don't see a standby pin anywhere? When I unplug main board all the voltages are low like what happens if main board plugged in and standby light goes off.

Also I don't know how this tv functions when it's working properly. Not sure if the white light is present when the tv is turned on or if it's usually always on in standby

[R_J]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

service manual: https://www.electronica-pt.com/esque...ileinfo/25756/

[caphair]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

service manual: https://www.electronica-pt.com/esque...ileinfo/25756/

Thanks. I'm not seeing anything about standby power though? Has a few p-on voltages but nothing about standby power?

[R_J]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

This looks like an always on power supply, AL+3.3v is the standby for the main (micro etc.)

[caphair]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

This looks like an always on power supply, AL+3.3v is the standby for the main (micro etc.)

Ok then measuring that it is 3.3v all the time even when I get the white standby light and when it goes out.

Also it stays at 3.3v with the mainboard disconnected

[R_J]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

I think P-ON-H1 is the power on line (page 61), then goes to (page 49) CN301-9

[caphair]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

I think P-ON-H1 is the power on line (page 61)

Should I jumper 3.3v to that line with mainboard disconnected to see if the rest of the power supply comes on?

[R_J]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

As you can see the circut is complicated, I think if cn301 is disconnected, 3.3 volts applied to pin 9 should turn on the voltages to their respective circuits, the power supply itself should already be on

[freakaftr8]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

What's your PFC doing? Check main filter capacitors at plugin then monitor for voltage drop..

[caphair]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

What's your PFC doing? Check main filter capacitors at plugin then monitor for voltage drop..

Stays at 151v all the time. Never drops

[R_J]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

If the power button is not turning on the tv It could be corrupt eeprom or bad connections on micro? (if it is bga)
There is no pfc circuit
Do you have all the supplies out of the transformer? ie c632 +31 C401 should have a negative voltage +15 volts on Q201 collector etc.

[freakaftr8]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

Don't think that can cause a voltage drop. 151v always means hv not coming up. Opto?

[caphair]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

If the power button is not turning on the tv It could be corrupt eeprom or bad connections on micro? (if it is bga)
There is no pfc circuit
Do you have all the supplies out of the transformer? ie c632 +31 C401 should have a negative voltage +15 volts on Q201 collector etc.

I have all the voltages that are labeled on the jumpers but they all drop to a half or lower once the white standby light goes out.

But it makes me wonder if the tv is powering itself on once plugged in then goes out. I'm not sure the normal behavior if there's usually a standby light or nothing until powered on, but pressing the power button does nothing.

The micro is a bga type. Should I try reflowing it?

[R_J]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

I'm going by the schematic, and I don't see the jumper your talking about. there are voltages like INV+31 on D632 (K) and PANEL +15 they should be there all the time. are you saying they drop in half?

[caphair]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

I'm going by the schematic, and I don't see the jumper your talking about. there are voltages like INV+31 on D632 (K) and PANEL +15 they should be there all the time. are you saying it drops in half?

If you zoom in on the psu you'll see a bunch of jumpers, they're all labeled for the voltages etc. I've been measuring there

And yes all the voltages either drop in half or more. For instance the 31v will be present until the white led goes out then it drops to 6v

The only constant voltage seems to be the 3.3v always which never changes

[R_J]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

It's imposible to know where a jumper on the board is located in the schematic. So if the main power supply is being controled there is only one place that can be. They must be changing the voltage on IC601 optocoupler via Q633 with the P-ON-H2 line
Going by the block diagram, P-ON-H1 & P-ON-H2 are controled by the micro. One of the lines controles 2 transistors Q3005 & Q3006 which seem to be on the main board.
You could check those two lines and see how they change when power is applied and the light comes on

Another line that seems to go in and out of a few different plugs is the KEY-IN1 line, thats the input from the keyboard/power switch, I would check and see if that line is changing when the power button is pressed, I would check it where it connects to the power supply cn102 then follow it through the other plug to the main board and then to the micro

[caphair]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

Voltages when the white led is on (both drop to 0v when it goes out)

P-ON-H1 = 3.3v
P-ON-H2 = 1.5v

Voltage present at all time (with or without white led)
KEY-IN1 = 3.3v drops to 0v when pressed
No continuity from the cn102 to cn301 though and 3.3v is not at cn301 where connects to mainboard even if mainboard disconnected still 0v at pin 29 of cn301. Can’t find if there’s anything in between the two connectors that would cause an open. Looking at the schematics am I right to say that KEY-IN1 becomes VCOM-PWM?

Going by the service manual, it seems the white led is linked to P-ON +5 so it appears the set it auto turning on when first plugged in. Would this be normal operation? A power on test? Or something wrong with microcontroller?

[R_J]

Re: Philips 19pfl3505d/f7 - No Power - Voltages drop

KEY-IN1 goes from CN102 (4) to CN302 (29) Then to CN3702 (29), R3703 (100ohm) then to IC3301 (AC5) [page 57]
I think you mixed up CN3702 (pin29) KEY-IN1 with CN3701 (pin29) VCOM-PWM
I don't know how "this tv" works, but sometimes they turn on the power supply at initial power on to make sure all voltages etc are there and ok, then turn it off again and wait for the power on to be pressed.