Philips PLCD190P5 power supply

[R_J]

Re: Philips PLCD190P5 power supply

This power supply is a bit rare and not much information is available. the other plcd150,170,190P1 schematics are different. I am guessing that the circuit you repaired is for the standby +5, correct. If pin 11 is the control line (ON/Off) for the power supply does it change if you press the power button? It could be that the line needs to be taken low, try what budm said, place 100Ω from that pin to ground and see if the other voltages come up

This should be the path from pin 11 that controls a couple transistors that control an opto isolator, That opto should be the one that turns on the main power supply, again no schematic so its a bit of a guess.

[The Performer]

Re: Philips PLCD190P5 power supply

This power supply is a bit rare and not much information is available. the other plcd150,170,190P1 schematics are different. I am guessing that the circuit you repaired is for the standby +5, correct. If pin 11 is the control line (ON/Off) for the power supply does it change if you press the power button? It could be that the line needs to be taken low, try what budm said, place 100Ω from that pin to ground and see if the other voltages come up

Yessir, am sitting in front of it now, tried both ways, no luck. I am probing around in the l6562 part of the circuit (from what I understand about power supplies is this area should provide the high voltage via the P20NM50FP mosfet by switching on and off through a transformer?) anyway, I am not seeing any drive waves in this area coming from the L6562 I replaced, my question is should I?

[R_J]

Re: Philips PLCD190P5 power supply

So the standby circuit is working, the L6562 is for the PFC circuit. What voltage do you get on pin 8 (VCC) On some power supplies the pfc runs all the time, on some they are switched on and off. On the PLCD300p3, the pfc, which uses the same ic, has its vcc turned on and off by a transistor. That plcd300 pfc circuit looks very close to yours, It drives 2 fets where as yours only drive 1
If the pfc circuit is not running, the circuit for the +12 may not run either as the supply for it would be too low.
There is a green wire that runs beside the main filter, does one end connect to pin 8 of the L6562 and the other end connect to a small transistor
That 14 pin ic to the left in the picture I believe is the standby drive ic

[The Performer]

Re: Philips PLCD190P5 power supply

R_J I am measuring .1v on pin 8 of the L6562, and there is indeed a wire jumper coming from pin 8 and it goes towards that smd transistor you are describing.

Are you possibly suggesting that I may need to look into what is going on with the standby drive ic?

[R_J]

Re: Philips PLCD190P5 power supply

NO the standby drive is working just fine. These are complicated power supplies, I suspect that when IN standby, the PFC circuit (L6562) is not powered. When the main board tells the power supply to turn ON, thats when a transistor, somewhere, applies the Vcc to the (L6562) and the PFC circuit boosts the b+ from 160 volts to 400 volts.
When the pfc voltage is at 400 volts, the circuit that supplies the +12-16 & -12-16 volts gets turend on.
There are 3 seperate power supplies on this board
one: is the standby +5 volts which is working.
two: is the PFC boost supply, which is not being told to turn on.
three: is the supply for the other voltages, and needs the pfc to working for it to operate. It too is likely controlled by the on command.

[R_J]

Re: Philips PLCD190P5 power supply

If you look at the PLCD300P3 schematic, on page 2 is the PFC circuit, just like yours except it drives two fets instead of just one.
On the L6562 pin 8 vcc. the supply is VCC_PFC . looking to the left is T100, its Collector gets voltage from V_PFC (which is supplied by the standby circuit) and when the base gets turned on supplies the voltage to: VCC_PFC.
transistor T101 is the stby switch, it recieves the on command from the main board and turnes on, lighting the led in the optocoupler turning on T100
Since there is no schematic for your board, these parts need to be identified on your board.

There should be a power on/off command coming from the main board, that MUST be there for the power supply to turn on.
without that command the power supply will sit in standby forever
Being that this is a %&*# Philips, it could be something on the main board that has detected a fault and not allowing the tv to come out of standby.

[The Performer]

Re: Philips PLCD190P5 power supply

If you look at the PLCD300P3 schematic, on page 2 is the PFC circuit, just like yours except it drives two fets instead of just one.
On the L6562 pin 8 vcc. the supply is VCC_PFC . looking to the left is T100, its Collector gets voltage from V_PFC (which is supplied by the standby circuit) and when the base gets turned on supplies the voltage to: VCC_PFC.
transistor T101 is the stby switch, it recieves the on command from the main board and turnes on, lighting the led in the optocoupler turning on T100
Since there is no schematic for your board, these parts need to be identified on your board.

There should be a power on/off command coming from the main board, that MUST be there for the power supply to turn on.
without that command the power supply will sit in standby forever
Being that this is a %&*# Philips, it could be something on the main board that has detected a fault and not allowing the tv to come out of standby.

R_J thank you for both of your replies, I will do further probing around and find the standby transistor. The schematic you are speaking of for the PLCD300P3 pg. 2 is I am assuming in the available service manual. On another note, what is common practice to test an optocoupler that is in circuit? I understand the concept but have never tested one in circuit.

[R_J]

Re: Philips PLCD190P5 power supply

Here is the PLCD300P3, I thought I already uploaded it, but it was a different one in post #2
Optocouplers can be hard to test in circuit. You should be able to thest the led with a meter (diode test) the output can be hard, it usually should check open or high resistance, but if the led is lit, the resistance would be low.
Its not likely the opto is the problem.
Did you ever try taking pin11 to ground and see if you get vcc on pin 8 of L8582. I would not worry too much about getting 12 volts but see if the voltage across the main filter goes from 160 volts to 400 volts.
You could also as a start, check the voltage on the optcoupler (cold side) I pointed out in the picture (post #21) check the voltage on the 2 pins (using chassis ground), then ground pin 11 and see if the voltage changes on one of the pins.
To measure the voltage on the other 2 pins (hot side) you would need to use the main filter ground for your meters ground.

[budm]

Re: Philips PLCD190P5 power supply

If you figure out which opto is used for PS-ON then all you have to do is to short the E-C pins (which will be on the HOT side) of the opto to simulate PS-ON present and see if the rest of the power supply will come on or not.

[The Performer]

Re: Philips PLCD190P5 power supply

Will update on both of those two suggestions with results soon, thank you very much both of you.

@Budm I wondered in past instances if there was a way to bypass optocouplers, but because I understood it as a photo resistor/transistor I did not know an actual closed switch symptom happens, thank you for that!

[R_J]

Re: Philips PLCD190P5 power supply

if the optocoupler is just acting as a switch, like in the case of turning the supply on and off, it is ok to short the transistor (optos output) BUT if it is for the feedback of a regulated supply, shorting it could tell the power supply to run at full output which could increase the voltage on the secondary higher than what it is designed for.
So it depends on the circuit as to weather you can short it or not

[budm]

Re: Philips PLCD190P5 power supply

if the optocoupler is just acting as a switch, like in the case of turning the supply on and off, it is ok to short the transistor (optos output) BUT if it is for the feedback of a regulated supply, shorting it could tell the power supply to run at full output which could increase the voltage on the secondary higher than what it is designed for.
So it depends on the circuit as to weather you can short it or not

+1, you need to know what function the Opto is being used first.

[The Performer]

Re: Philips PLCD190P5 power supply

Ok so got some news, I have found that by removing the mosfet I replaced and testing I finally get my 12v on pin 8 of the pfc controller. I need to check that I have a suitable mosfet, (I thought I got a suitable replacement... Also, I have found that the resistor immediately in line of the PFC controller's 7 pin (gate drive for the mosfet?) has what appears to be a burn line down it. I cannot make out the markings. In the schematic R_J has given me it shows to be R110, and value 100R (100 ohm) I am assuming? Now, that being said if I scope pin 7 of the PFC controller, I get (what I can tell to be) a smooth 10v DC... I would have thought to see a square wave?

[The Performer]

Re: Philips PLCD190P5 power supply

Here are some pictures of my measurements (A 100 ohm resistor across ground and PS standby pin 11 of the connector does indeed turn on the PFC controllers VCC)

These measurements have X066 Mosfet removed. The mosfet I used to replace the shorted original is a FDPF 18N50. I used a website that gave it to me as a cross reference because the original part number was not on digikey if I remember correctly...

The resistor between the mosfet gate and pin 7 of the PFC controller is burnt looking and measuring 1.2 meg ohm...

So now looking forward, I am going to research and verify the mosfet I ordered is not to blame and causing the issue, as well as I believe I am going to solder a 100 ohm resistor temporarily in place of the burnt looking one.

Based on what I am finding do you guys believe I might be heading in the correct direction?

Also, the schematic you have given me R_J is great, thank you very much. Like you said it's not identical to my board but does look like it's using alot of the same concepts. Hopefully I can use some of the values where I need on my board that cant be identified.

[budm]

Re: Philips PLCD190P5 power supply

If the Gate drive (R/D network and anything that is connected to the Gate need to be tested) for the PFC MOSFET is damaged then you need to replace the PFC IC too since the Gate drive output if the PFC is more likely to be damaged also.

[The Performer]

Re: Philips PLCD190P5 power supply

If the Gate drive (R/D network and anything that is connected to the Gate need to be tested) for the PFC MOSFET is damaged then you need to replace the PFC IC too since the Gate drive output if the PFC is more likely to be damaged also.

Low and behold, Having the PFC mosfet out, I just tested it with my meter and turns out its bad now... It's not shorted but not passing diode checks.

Checking out around the PFC circuit again Ive found that both resistors (the burnt looking one) and the one next to it (labeled 330) are reading in the meg ohm range. Based on pictures of good boards it looks like my burnt resister is the same as its neighbor a 330 (33 ohm)

I see that in my board there is no gate drive transistor like in the schematic I am looking at. It appears the PFC controller directly (through the 33 ohm resistor of course) drives the gate?

So now it looks like I need to replace the mosfet (again), the two resistors connected to pin7... I really wish I had an N-channel fet to slap in and test before ordering another. I cant say it looks like the PFC controller is bad, but I ordered 2 so I have a backup.

Thoughts?

[R_J]

Re: Philips PLCD190P5 power supply

You might be able to use that scope/meter to see if there is a pulse coming from L8582 pin 7 when the board it turned on. (fet can be out during test), but I suspect the ic is bad. they don't like 150v applied to them.
The fet you ordered should be ok but is rated a couple amps lower than the original.
If the fet is not shorted it may still be ok, It won't test like a transistor Check this video. https://www.youtube.com/watch?v=tL7bQuJaXKA
If the 33Ω was open going to the gate the fet would not see the drive signal, so was it open before and you did not notice? try replacing it, install the fet and see if it works.
The schematic I posted in #2 uses a circuit closer to what you have off pin 7, it uses a 10Ω & 100Ω, yours uses two 33Ω
One of the 33Ω is in series with a diode, check the diode but it is likely ok.

[budm]

Re: Philips PLCD190P5 power supply

Check the resistance between Gate Drive pin and Vcc pin of the PFC IC to see what you have, same test between Drive pin and GND. The output of the PFC IC may stuck high or stuck low depend on what kind of damage it has, if it stuck high and you did not replace the IC but replace other damaged parts in that section then when you apply power the new MOSFET will be fully on instated of switching on and of, then the new MOSEFT will be damaged and blow the main fuse.

[The Performer]

Re: Philips PLCD190P5 power supply

Ok so got some measurements, with the mosfet in place, both 33 ohm resistors replaced as soon as I power on the supply it idles for a second, then (shorts/faults) since my 25 watt inline cord lightbulb glows bright for a second or two, then off, then the cycle repeats endless.

I removed the mosfet, re did the test and no apparent issues, I read pins of the PFC controller and all look ok, except the gate driver pin 7 only shows a steady (no drivewave present at all) 10.5v dc. I was under the assumption that even without the FET present I should still see a driveway right? Otherwise, VCC is at 12v all fine as should be, Drain pad of the FET shows 160v, all seems right.

Now, as I said, I am sure the FET is bad, I perform the diode test and only reading I get is a source- drain .49v drop, no continuity or resistance on any other pins in any configuration.

As far as the PFC resistance readings Budm asked about, I have 42.7 kohm from GD(pin7) to ground, and 1.3mohm from GD to Vcc(pin8)

Now, that all out, as I said I have one more pfc controller, should I replace it, leave mosfet out, and test if I have drive wave on pin 7 (GD) ? Then order another mosfet and the other parts I need?

Also, do you guys ever keep generic N type and P type mosfets on hand for just throwing in a circuit to test prior to ordering the specific ones? It would be nice if I had one to throw in and verify if I need more stuff before making my next order, (incase I find I need MORE parts)...

ANyway, thank you guys! Hopefully I can get this up and running. if not ive learned a little more.

[R_J]

Re: Philips PLCD190P5 power supply

The fet WILL NOT check like a transistor. I refered you to a video on how to check a fet with a multimeter.
When the supply was trying to start, did you check to see what the pfc voltage was? accross the main filter cap.
I would be using a 60 watt lamp, not sure how the supply will act with a 25 watt lamp. I would think that the lamp would light with only 200ma of current going through it.