issues with 272217100571 power supply from Phillips 47PFL3603D/27

[Pioneerx01]

When I originally got the TV it was completely dead. When comparing the replacement parts to the ShipJimmy Kit (part 1) I have lot of bad components this kit addressed so I bought it and replaced all the components for part 1. The PSU now has stand by voltage, but I am having problems with 12V and 24V supply. When I manually turn of the PSU the 12V reads 3.4V and 24V reads 7.4V. I have been trying to trace the 12V line on the PSU board, but I keep chasing my tail and can't find an obvious issue. This is were my lack of PSU design knowledge is apparent.

Any ideas what I should look at?

I have attached images of the PSU from ShopJimmy site, as they have higher res pictures that I can take.

Thanks for your input.

[budm]

Re: issues with 272217100571 power supply from Phillips 47PFL3603D/27

Are you getting close to 400VDC between the two legs of the main filter caps in the primary side?

[Pioneerx01]

Re: issues with 272217100571 power supply from Phillips 47PFL3603D/27

Yes, 398VDC on each one of them.

[budm]

Re: issues with 272217100571 power supply from Phillips 47PFL3603D/27

Since T201 is for generating the 12V and the 24V so something has to be in common which can be the drive circuit or the feedback circuit.
The parts you received, are they for fixing the 12V/24V power section also?

[Pioneerx01]

Re: issues with 272217100571 power supply from Phillips 47PFL3603D/27

I am not sure what do the transistors or the ICs of the kit do exactly. I have highlighted the ones I have replaced (Part1) in red, basically all but the fuses, they were OK. The capacitors that came with the kit were undersized to what was on the board originally, so I have used mine to match the values. I have also replaced 4 additional caps that were not in the kit, as they looked a little funny. All parts were factory original initially, no one worked on this board before me.

http://www.shopjimmy.com/philips-272...repair-kit.htm

While the T201 Transformer is receiving 327V and 58V on the hot side, it is completely dead on the cold side. The 3.4V and 7.4V are coming from somewhere else. I am reading those voltages on the common cathode of the diodes (in blue)

[budm]

Re: issues with 272217100571 power supply from Phillips 47PFL3603D/27

"While the T201 Transformer is receiving 327V and 58V on the hot side, it is completely dead on the cold side. The 3.4V and 7.4V are coming from somewhere else. I am reading those voltages on the common cathode of the diodes (in blue)" You are using the wrong ground when you make the DCV reading on the hot side that sis why you are getting the 327V and the 58V readings, when DCV in the Hot side of the circuit, you have to use the negative leg of the main filter cap as the GND ref. for your meter, do not use the chassis GND. If T201 is dead there is no way you will get those Voltages since they are rectified by the Diodes on the cold side, and your AC meter also does not have the bandwidth to measure 50K~100KHz range on the secondary winding of the transformer.
All those red markings you made to show the parts you had replace are just about cover all the sections of the power supply circuits: The PFC, the Standby power supply, the 12V/24V power supply, and the inverter circuit.

[Pioneerx01]

Re: issues with 272217100571 power supply from Phillips 47PFL3603D/27

I have re-measured the voltages with the filter cap ground, and I got 400V on the legs that I got 327V initially. The others on the hot side are getting 0V with caps as a ground.

Stupid me measured the output on cold side of the transformer in VDC not VAC. I get 16.5VAC and 9.4VAC, with caps as a ground. I am not sure if that is the correct way to measure the output.

Based on the specks my multimeter should be able to handle 200KHz. If you can tell me what to measure and how, as I have never measured frequency, that would be great.

Thanks

[CapLeaker]

Re: issues with 272217100571 power supply from Phillips 47PFL3603D/27

Check again the 12V and 24V rail (cold side) with meter set to DC.
If you measure something DC on the hot side, you use the negative of the main filter cap as ground.
If you measure DC on the cold side you use any GND on the cold side.

[Pioneerx01]

Re: issues with 272217100571 power supply from Phillips 47PFL3603D/27

DC voltages on the cold side still read as they did before. 12V reads 3.4DCV and 24V reads 7.4DCV.
That's either with the ground prong on the chassis, or on the ground pin of the connectors.

[budm]

Re: issues with 272217100571 power supply from Phillips 47PFL3603D/27

So the output Voltages are about 30% of what they should be for the 12V/24V.
Please check the snubber diode D201 in the primary side of the 12V/24V power supply section, you need to lift one leg off the board for testing.
PC201, IC U202 are for the feedback for regulating the output Voltage.
Something in common is causing the output Voltage to be low.

[budm]

Re: issues with 272217100571 power supply from Phillips 47PFL3603D/27

BTW, you already test the diodes in the secondary side of the 12V/24V/+/- PS for audio section, right?
Also need to see the sticker of the TV model number to see the Chassis number so we can look up the service manual for it.
Chassis number Q522.2E, LC8.2A?
BTW, the power supply-inverter board is made by LG so Philips service manual does not include the diagram of the LG board.

[Pioneerx01]

Re: issues with 272217100571 power supply from Phillips 47PFL3603D/27

Chassis # LC8.1U LA

I took the D201 out of circuit and it measured 0.412V drop which is a little low so I replaced it with new one; but no dice.

As to the testing the diodes in the secondary side of the 12V/24V/+/- PS for audio section; I don't know which ones they are. Are they those big rectifier type diodes (D233, D234)?