Sony KDL 32L4000 Troubleshooting

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

Bud,

My apologies for all frustrations working with me, but I am trying to make sure I am correctly hearing what you are saying and am truly appreciative for your efforts.

I had asked if I could troubleshoot the power board by connecting to line power without having the board installed in the TV. Now that I have the TV working because of your unceasing support I have it back together and am using it. I can pull it apart to power the old board for testing if that is required. I understood you to say that the board could not be properly worked on outside the TV without grounding the PS_ON. Since I was getting weird outputs from the power pins I understood this to mean that I wouldn't get any readings on a good board without grounding and thus my comment about not needing to ground it since 202 on the good board was also giving me voltages.

But as I re-read our discussion I believe what you were trying to tell me was that in order to test all the voltages we need to the low voltage on PS_ON because that is what will completely "energize" the supply and create all the output voltages.

Assuming I am now on the same page with you, it would seem to follow that in order for a working power board to power on the only thing I need from the main board is to provide a low voltage reading to PS-ON and thus grounding that pin would provide the same results. Therefore, it would seem that the best way to troubleshoot and test this board would actually be to work with it outside the TV and ground the PS_ON as this will remove any external issues and allow me to use the TV while troubleshooting. Is this correct?

It is also my understanding that to ground the PS_ON pin all i need to do is make a connection from PS_ON to the ground pin 4, 5 or 6? Is this correct?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

Yep, juss run the power supply board on the bench by itself first without grounding any pins, just supply the 120Vac to the board, if you are hearing the RL1 clicking on and off then we need to find out why, I believe the key is to find out why the RL1 is clicking on and off without anything connected to the power supply board.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

OK, Great!

Going back to your power supply tutorial, you mentention that:

The power supply has Standby 5vdc (5VSB, this is a MUST have before anything else will work, when this voltage is not present ... This 5vdc is used to power the Processor and the Infrared remote receiver module which will be waiting for the command from the remote control or from the power switch, when the Power on command is received, the Processor will send the turn on signal (3.3~5vdc) to the power supply module (PSON pin) to the switch on the main 5vdc for the rest of the logic and Tuner circuits, 12~16vdc for the sound amplifiers (mostly Class D amplifier for efficiency and small size) and for the T-CON board (interface board between the LCD panel and the Logic board), and 24vdc for the Back lights inverter board (if there is no 24vdc then no back light).

The power supply converts the 120/230vac 50/60Hz into DC, then the high frequency (50~100kHz) switching circuits convert it back to AC but at high frequency which allows the power supply to use smaller and much lighter weight transformers (Ferrite core instead of heavy iron core), then this high frequency AC voltage is fed to the rectifier Diodes to get the DC output and filtered by DC filter capacitors...

Thus at a high level a power board needs to have a section that receives 120VAC, a section that converts this to DC, a section that reconverts this back to high frequency AC then sections to convert this to each of the needed DC output voltages. Assuming this high level understanding is valid what we know is that 120 VAC is being received, it is converting to DC and then converting back to AC as we are getting 4VSB (standby voltage on this set) on 202. It seems that the problem is that once the signal to turn on the rest of the voltages comes in the board fails to do this.

Is this a correct understanding?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

So right now on your bad power supply board, when we GND the PS-ON pin (your board uses Active LOW instead of Active HIGH), then the PFC Voltage booster should come on and boost the Voltage on the filter cap to around 380 ~ 400VDC and the rest of the power supplies should come on when the boosted Voltage is present.
The rest of the power supplies on you board require two things, it needs PS-ON and the PFC Voltage to work, the power supply board without PFC Voltage booster will only require the PS-ON.
In the earlier test I have you run the power supply board by itself and have you GND the PS-ON pin but the Voltage on the cap remain at 160V.
The strange symptom we are having is that the RL1 is clicking on and off when you run the power supply board by itself WITHOUT GND the PS-ON.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

Bud,

The schematic shows a polarized connection, but the board does not (though the plug is keyed). Is it important to get polarity correct when externally working on board?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

Are you talking about the AC connection? It has Line (L) and Neutral (N).

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

Yes, I am talking about the AC connection. If I plug the board into the TV the connector is keyed and can only be plugged in one way; however, if I test it outside the TV I need to make up a plug to connect and the question is do I need to worry about the orientation of this made up plug.

It is marked as Line and Neutral on the schematic, but not on the board or component layout. From what I make out of the schematic, if the board has CN1 in bottom left then Line is the top connection and Neutral is the bottom connection. Is this correct?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

https://www.badcaps.net/forum/attach...8&d=1532287485
Can you not remove the AC inlet which is screwed in place and use the power cord that cones with the TV.
BTW: Brown wire is Line, Blue wire is Neutral.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

I could remove it, but one reason for working with the old board outside the TV is so I can use the TV. If I remove the connector then I can't use the TV.

I should be able to make up a connector to fit. Looking at the schematic the line connects to the fuse. On the board it looks to like the top pin connects to the fuse. Am I reading this correctly?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

As I indicated, Brown wire is the Line which is connected to the fuse.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

I have a second TV, Samsung Plasma, that also has problem turning on. Should I start a new thread or talk about it here?

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

OK, I got the board set up for testing and checked the DC voltage across the main cap both without anything other than line plugged in and with PS_ON shorted to ground. In both cases the voltage fluctuated between about 260V and 295V. You had suggested I would be seeing around 160V with nothing connected and around 360V with PS_ON grounded. What does this tell us?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

That means the Voltage boosting is taking place but does not come up to the correct Voltage, so PFC section has to be looked at first. Check the DCV at the VCC pin of the PFC IC to see what you get.
The PFC circuit may have feedback problem. BTW, the main filter cap checked OK, correct, no sign of any liquid leakage or any thing like that, correct?

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

To my untrained eye I see nothing out of the usual in the condition of the cap.

I am assuming that PFC is IC31 pin 8. If this is correct I am assuming pin 8 is top left with writing. Is this correct?

Also do I want to ground ps on or leave everything unconnected when I measure?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

Just look up the spec sheet of that IC31 so you can learn how to count the pins on the IC.
PS-ON pin will be grounded to turn on the main power supply.

[budm]

Re: Sony KDL 32L4000 Troubleshooting

Just look up the spec sheet of that IC31 so you can learn how to count the pins on the IC.
PS-ON pin will be grounded to turn on the main power supply.
BTW, when you power up the board with PS-ON pin grounded, do you hear the relay RL1 click on?

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

I had looked up the spec sheet for IC 31, but couldn't figure out the correct orientation for the SMD version. https://cdn.badcaps-static.com/pdfs/...1fdeef964c.pdf The through the hole versions have the notch or dot which is orientated to the left, the SMD seems to have a mark in the lower left from their drawings. However, the chip on the board is barely readable and I don't see any kind of dot, but can see the orientation of the barely readable writing. I am assuming that the bottom left with relations to the writing orientation will be pin one. That is why I asked, is that the traditional orientation?

Also should I use the ground pin on the chip or what would be the best point to check the vcc pin against?

You may recall that the relay clicks continuously on this board regardless if the PSON is grounded or not. The only way the relay does not click continuously is if all connectors are connected; then it clicks once at startup but will not click again, even when the power button is pressed.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

There could only be two orientations for pin 8, one give no reading the other cycles between 0 and about 2VDC for Vcc on IC 31 and from what I am reading on the data sheet it is looking for a 12 VDC. The second case was the one I assumed was correct with pin 8 being top left with chip writing right side up.

Since PS_ON is grounded we are getting 0 VDC which should be turning on the PS; it is not completing that operation and seems to keep cycling to try as I am hearing the relay continue to click. I thought that there was a fail safe to stop this if it cannot complete the task after a number of tries so that the relay would stop, but if so it isn't working.

[budm]

Re: Sony KDL 32L4000 Troubleshooting

That relay operates from the same 12V (VAUX2) that feeds the PFC IC.
At this point we need to find out why the relay is power supply is going on and off by itself WITHOUT PS-ON being Grounded, you had already verify that your new power supply board was not clicking when it runs by itself without connecting to the main board per post 37:
Quote:
Since you have working board right now then you should record the Voltage readings of all the pins on the power supply to have it as future reference.
See attached pdf. PS ON is 4.16 in standby and 0 once powered on. Same if board only is powered and the connectors are not plugged in. So it seems that you don't need it tied to ground in order for the board to work, only to power on the board.

Quote:
BTW, if you run the power supply board by itself without having it connected to the main board, do you hear RL1 clicking like what you have with your bad board?
Reply: No it doesn't.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

At this point we need to find out why the relay is power supply is going on and off by itself WITHOUT PS-ON being Grounded, you had already verify that your new power supply board was not clicking when it runs by itself without connecting to the main board per post 37:

Correct, the new one does not exhibit that characteristic. How do I go about figuring out why the relay continues to cycle rather than power up the board?