Philips 75pfl5704/F7 No sndby power

[CurtisC]

Hello everyone. I'm brand new to the group. I'm trying to fix this Philips 4K TV. I have minimal experience with most of this so forgive me if I don't understand half of what is posted on these forums. I'm trying to find my way through it.
Basically I got the TV from a previous owner who said it just died on them. So I wasn't there when it broke. It will not power on, no lights, no backlight, no sound.
The output of the power supply has a 27 pin connection to the main board. Pins 18-27 (labeled P-On+20v) are the only pins reading power at 12v each. The pins marked ALL+3.3v, which I understand to be the standby power measure no power. The ground pins are all grounded to cold ground. All other pins according to the manual (if I'm reading it correctly) should have around 3v but I cannot measure more than .04v on any of them. I have only measured these with the ribbon cable removed as it's difficult to measure attached.

With that information can it be concluded that the power supply board is probably malfunctioning?


This is the only tech manual I could locate for the TV model:
https://www.manualslib.com/manual/22...page=58#manual

I appreciate any input you may have. Thanks for reading.

[KevM]

Re: Philips 75pfl5704/F7 No sndby power

hi A couple of things to check early on is the main fuse located next to the mains input. check continuity of this. if its reading open then you probably have component failure on power board. Look for anything thats burnt or has a hole in.
If its ok then chack you have power coming into the tv.
if standby light is not on at all then nothing will work.
Just be careful poking around on a power board there are some high voltages on there. post pics of boards
Im sure someone with more experience than me can help you further when you post pics.

[bohaboha]

Re: Philips 75pfl5704/F7 No sndby power

Hello everyone. I'm brand new to the group. I'm trying to fix this Philips 4K TV. I have minimal experience with most of this so forgive me if I don't understand half of what is posted on these forums. I'm trying to find my way through it.
Basically I got the TV from a previous owner who said it just died on them. So I wasn't there when it broke. It will not power on, no lights, no backlight, no sound.
The output of the power supply has a 27 pin connection to the main board. Pins 18-27 (labeled P-On+20v) are the only pins reading power at 12v each. The pins marked ALL+3.3v, which I understand to be the standby power measure no power. The ground pins are all grounded to cold ground. All other pins according to the manual (if I'm reading it correctly) should have around 3v but I cannot measure more than .04v on any of them. I have only measured these with the ribbon cable removed as it's difficult to measure attached.

With that information can it be concluded that the power supply board is probably malfunctioning?


This is the only tech manual I could locate for the TV model:
https://www.manualslib.com/manual/22...page=58#manual

I appreciate any input you may have. Thanks for reading.

Hi help those who want to help you post some nice pictures on tv plus some other nice pictures on the back so they can see everithing pws, mainboard, all good luck

[CurtisC]

Re: Philips 75pfl5704/F7 No sndby power

I went ahead and purchased another board off eBay but found that one is also not supplying standby, which I assume is labeled ALL+3.3V since there is no other logical marking. This board in the pictures is my original power board. I have done some poking around however I have no idea if I'm testing correctly. Ive been going off youtube videos from TV repair channels and the like. I am testing using cold ground on Cold side, and using negative capacitor pins as Hot ground.

I know the fuse is good. Main 400v caps all get power. Ive tested most of the FETs to ground and none seem shorted to cold/hot ground. (Saw someone do this on YouTube https://www.youtube.com/watch?v=x-fhJsV9V5E, no idea if it helps) all the P-ON+20 pins on the cable port are reading 12.5vdc. All caps look okay, no bulging. No holes or burns that I can see in anything else. I have tested some diodes to see if any read forwards and backwards. I think I found one (D1701 that connects to transformer1701 which powers the LEDs, it's tiny and on the back so it's possible I am testing it wrong too) but it isn't on the circuit for the standby. All others test 1 on a volt meter when reversed. Again, not sure if that's helpful.

I'm trying to trace from power in, to the T601 Transformer since none of the cable connections connected to it are powering up.
Let me know if there is something else you'd recommend or pictures you need.

Thanks

[nomoresonys]

Re: Philips 75pfl5704/F7 No sndby power

Pictures are not quite clear enough to see it, can you give a good picture of that D1701?

[CurtisC]

Re: Philips 75pfl5704/F7 No sndby power

Here you go

I'm reading 707 one way and 623 the other. Not sure which is pos and neg.

[nomoresonys]

Re: Philips 75pfl5704/F7 No sndby power

Not exactly sure, maybe it's reading both ways because each side is leading to resistors, measured a couple diodes on a board, some read like you would expect, a couple read 100 both ways a couple read 30 both ways, I believe this board is good if I remember it's from a broken screen tv.

[CurtisC]

Re: Philips 75pfl5704/F7 No sndby power

Not exactly sure, maybe it's reading both ways because each side is leading to resistors, measured a couple diodes on a board, some read like you would expect, a couple read 100 both ways a couple read 30 both ways, I believe this board is good if I remember it's from a broken screen tv.

I just tested it on the replacement board that I have to send back cause its not supplying standby either, and they both read the same.

Think I may have hit a dead end. I'm just not experienced enough with this.

[CurtisC]

Re: Philips 75pfl5704/F7 No sndby power

How can I test if there is power getting to the transformer on the hot side of the board? Do I still use a neg terminal of a cap for ground?
I don't want to do more damage.

[nomoresonys]

Re: Philips 75pfl5704/F7 No sndby power

If the pins you are testing are on the hot side which should be clearly marked with the thick line, then yes. Now if the legs come out on the cold side then use chassis ground on that cold side.

[CurtisC]

Re: Philips 75pfl5704/F7 No sndby power

If the pins you are testing are on the hot side which should be clearly marked with the thick line, then yes. Now if the legs come out on the cold side then use chassis ground on that cold side.

Thanks for the assist!

[R_J]

Re: Philips 75pfl5704/F7 No sndby power

This board does NOT supply AL+3.3V, it is created on the main board from the P-ON+20V which will be low (12v) when the tv is in standby. The power supply ON signal will be on CN651 pin4 (P-ON-H2) it should be 3.4v
If you are getting +12v on the P-ON+20V, the power supply is working (in standby) so no need to check components.

On the digital main board, P-ON+20V supplies IC3605(2) which outputs +5V on pin 3, this regulator supplies IC3504(3) which output +3.3V on pin2

[CurtisC]

Re: Philips 75pfl5704/F7 No sndby power

I tested the transformer (T601) and it had around 400v going in from Hot but zero on the cold side. This was tested using cold ground on cold.

Is there anyone who knows by looking at the tech manual if this transformer may need to be triggered somehow? Or is this probably a failure point that I should replace?

Thanks

[R_J]

Re: Philips 75pfl5704/F7 No sndby power

DO you have any voltage on P-On+20v???? If yes, stop checking things on the power supply before you blow it up, IT is working.

The output of the power supply has a 27 pin connection to the main board. Pins 18-27 (labeled P-On+20v) are the only pins reading power at 12v each.

[CurtisC]

Re: Philips 75pfl5704/F7 No sndby power

This board does NOT supply AL+3.3V, it is created on the main board from the P-ON+20V which will be low (12v) when the tv is in standby. The power supply ON signal will be on CN651 pin4 (P-ON-H2) it should be 3.4v
If you are getting +12v on the P-ON+20V, the power supply is working (in standby) so no need to check components.

On the digital main board, P-ON+20V supplies IC3605(2) which outputs +5V on pin 3, this regulator supplies IC3504(3) which output +3.3V on pin2

Oh thank you this is what I was wondering. The P-ON-H2 (pin 4) on CN651 does not have any power when measured on the power board. And yes all P-ON+20v have 12v.

Sorry I didn't see your post until after I posted about the transformer. Greatly appreciate it!

[R_J]

Re: Philips 75pfl5704/F7 No sndby power

Check page 67 (if you have type A main board)

[CurtisC]

Re: Philips 75pfl5704/F7 No sndby power

,

Thanks, that's the one I've been using. I'm new to this so I wasn't sure how it worked but I was confused since the other PB I've seen people work with had a standby marking on the boards.

So even if P-ON-H2 has no 3.4v power the board is probably okay, and it is something else all together?

[R_J]

Re: Philips 75pfl5704/F7 No sndby power

The P-ON-H2 is the power supply ON signal sent by the main board to place the power supply in full ON mode, That signal is missing and likely due to a bad bga connection on the main board ic3001 or maybe a firmware corruption issue.

[CurtisC]

Re: Philips 75pfl5704/F7 No sndby power

The P-ON-H2 is the power supply ON signal sent by the main board to place the power supply in full ON mode, That signal is missing and likely due to a bad bga connection on the main board ic3001 or maybe a firmware corruption issue.

Ah awesome. I'll move away from the power board. The last owner took this set to a tech and they couldn't get it working, they just said it was the power board. I'm glad you knew better. Thanks a lot

[R_J]

Re: Philips 75pfl5704/F7 No sndby power

This is known as a always on power supply, in standby the pfc circuit and main switcher is not operating, and since the tv is off and under light load, the main ic601 is operating in burst mode at a reduced frequency, that is why the output voltage is low, If the power supply turned ON this voltage would be close to +21v instead of +12v