Philips 37PF7321/98 cannot turn on

[john_doe]

My Philips 37PF7321/98 LCD TV suddenly just cannot be turned on.

When I turn the power on, there is a green light on the right bottom of the TV. After a few seconds, it turns red and stay red. There is no picture or sound and the screen is black.

I have checked the capacitors marked in red circle and the resistor 3318 and all are ok. I check them out of circuit.

Any suggestions what should I check?

I am only a beginner in electronics troubleshooting. Please guide me.

Thanks.

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

Can anyone offer some advise?

Where should I check? Is the problem on the power supply board or should I look elsewhere?

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

I check the voltages at connectors 1304 and 1309 on the main power board and all pins have zero volt.

I then check the voltages of IC.

7005 and 7006 list on board
STP15NK50ZFP -> line 1 on IC
All pins have value but the values keep jumping

6019 list on board
STPS20L40CFP -> line 1 on IC
Pin 1 = 0
Pin 2 = 0.045
Pin 3 =0

7002 list list on board
ET1102 -> line 1 on IC
Pin 1 = 0.045
Pin 2 = 0
Pin 3 = jumping value (-1.something to -smaller value)
Pin 4 = jumping value (-0.5 to -smaller value)
Should I replace IC 6019 and 7002 or are there other places I should check first.

Any help would be greatly appreciated.

Thanks!

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

I also check 7001 (MC34067P on line 1 of IC). The value of all 16 pins are jumping and reducing.

Is it normal that the reading of most of the ICs I check are jumping? I thought the reading should be fixed.

Any ideas?

[selldoor]

Re: Philips 37PF7321/98 cannot turn on

I know very little about repairing tvs.
Have you checked all the fuses?
Was it all connected up when you did the voltage test
There is a black rectangular component at 1350 (could be a relay)
is there a hole blown in the top?

[ivoh]

Re: Philips 37PF7321/98 cannot turn on

I also check 7001 (MC34067P on line 1 of IC). The value of all 16 pins are jumping and reducing.

Is it normal that the reading of most of the ICs I check are jumping? I thought the reading should be fixed.

Any ideas?

start with the power supply. make sure its putting out proper voltages to the main board. the voltages might be listed next to the connector that connects the power supply and main board.

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

the first thing you need to do is check for voltages at the pins that send power to the main board.
Do any of those pins have voltages written next to them ?
A good picture of the bottom side of the power supply would help.
and a better straight down picture of the top would be good too because I can only see one of the numbers that you are referring to.

[budm]

Re: Philips 37PF7321/98 cannot turn on

So what resistance do you get on R3318? and the DC voltage on that cap you circle in red? The Blue rectangular cap that R3318 connected to also tested OK?

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

Both big fuses on power supply board are ok. Nothing is blown as far as I can tell.

There is 240v in to the power supply board.

The board does not label the voltages at the connector but I saw from the service manual that connect 1304 has two 12v and two 24v output.

R3318 has 465ohm and the Blue rectangular cap has 917nF.

Do I measure the DC voltage of the cap out of circuit?

Voltage measure of IC are done with all wires connected to the power supply board. Resistor and cap measurement are done out of circuit.

Thank you for your suggestions.

[budm]

Re: Philips 37PF7321/98 cannot turn on

Here is the service manual so you can do more voltage testing.

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

Thanks budm. I already have the service manual but I am very new to this electronics troubleshooting and will need lots of help.

The voltage of the cap:
C2022 - almost 0
C2038 - almost 0
C2066 - almost 0
C2041 - almost 0
C2043 - almost 0
C2018 - almost 0
C2034 - almost 0
C2003 - 4v and decreasing
C2002 - 1v and decreasing
Blue Cap C2319 next to R3318 - 50v and decreasing fast

Where should I check next? It seems that there is no current going to those caps.

[selldoor]

Re: Philips 37PF7321/98 cannot turn on

There is crater of some sort in 1350 does it look like its part of the moulding.
Is there a part number on the side

I asked if you had checked ALL the fuses -- there is a red barrel fuse ?

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

The crater at 1350 is a depression in the moulding. It is an Omron relay G5PA-1 5VDC. There is a click sound when I connect the power supply to 240v. Can I assume the relay is working?

The red barrel fuse at 1007, T5A/250V is label on board. I check the resistance in circuit and it reads 0.1ohm. I don't know whether I doing the correct thing to measure in circuit. Please tell me if I am doing it wrongly.

[selldoor]

Re: Philips 37PF7321/98 cannot turn on

You cant assume the relay is working properly - contacts may be burnt.
Well that fuse seems ok as well.

I have been looking at the base of the two BIG caps and the soldering looks a bit brown may just be flux or the picture. Just to check the conversion of mains to DC can you very very carefully check the voltage on those two BIG caps. You can take the board off to do that - work on a non conductive surface - connect it to the mains then with your meter on 600vdc put one probe on each contact. DO NOT touch anything else on the board and use a RCD breaker if you have one.
Keep the probes in place for a few seconds to see if the voltage is steady

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

The 4 volts looks like it might be in the feedback circuit so your 5 volts might be trying to turn on
this looks like it would be on the diode that has 3 legs and is by itself on the one heatsink and near the 2020 cap.
Do you get a slight burst of power there when first plugged in ?

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

I removed the power supply board as per selldoor's instruction.

The relay 1350 pin2 and pin3 has 240vAC, pin1 and pin4 has 0vDC. There is no click sound. Pin2 and Pin3 should be open but there is 240vAC. So this relay is bad?

The 2 Big Cap have 0.263vDC.

When the power supply board is connected with all wires, the 2 Big Cap have 65vDC and the value will decrease slowly. And there is click sound.

Bammbammfran - the diode u are referring should be 6019(See message #3). How do I check for the slight burst of power when first plugged in?

[selldoor]

Re: Philips 37PF7321/98 cannot turn on

Well something is wrong if you have mains of 240 vac then the BIG 400v caps
should be at 240*1.4 VDC - I will have a look at the schematic and the back of the board

Later

Ok 6306 is the bridge rectifier it has 4 pins the two inside ones are the AC in and
should measure the same as your AC Mains.
The two outside pins are DC and should be mains*1.4 vDC

Can you very carefully test that? make sure to change your meter to 600 vAC then 600 vDC

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

6306 has 240vAC on AC pins and 342vDC on DC pins.

I am measuring this with all wires disconnected except the main 240vAC.

[selldoor]

Re: Philips 37PF7321/98 cannot turn on

OK can you do the same test on 6307 - whilst I saw 6306 0n the schematic I cant just spot it on the board?

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

For 6307,the AC and DC voltages are almost zero. Shouldn't it have 240vAC as the pin2 and pin3 of relay 1350 has 240vAC.