Sony KDL 32L4000 Troubleshooting

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

That was one of the things I was trying to understand, whether all the voltages should be present at the start or if those voltages were only generated after the power on button was pressed.

Now I understand that all voltages should be present from the start. Thank you for clarifying that.

Are you associated with shopjimmy?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

That was one of the things I was trying to understand, whether all the voltages should be present at the start or if those voltages were only generated after the power on button was pressed.

Now I understand that all voltages should be present from the start. Thank you for clarifying that.

Are you associated with shopjimmy?

Nope, I use their website for pictures of the boards since they have lots of good quality pictures. I do buy boards from them and always get good service if the bad board is received.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

I figured I would use them if it were yours, but they don't have the board and have low expectations of getting one. I am working eBay for a source.

In the meantime, I am still interested in trying to understand more.

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 ... then this high frequency AC voltage is fed to the rectifier Diodes to get the DC output and filtered by DC filter capacitors

So we know that the board powers on and produces 4 VDC, but not the other voltages. What does this tell us about where the fault on the board might lie?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

Since we have the schematic this will allow us to trace out the circuit to find out if the SMPS IC's and various circuits are getting the switched VCC for the circuit to run or not.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

What is my approach to this?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

You will have to learn to read the schematics and able to trace the connections based on the schematic. You will need to plug the TV into at least the GFCI outlet in case you accidentally touch the connections on hot side of the boards which is where you will be checking. The board will have to be flipped over for you to access the test points of the power supply board.
The black probe of the meter will be connected to the negative leg of the main filter cap in the hot side of the board, then you will use red probe of the meter to check and see what DCV you have on the Emitter pin and on the Collector pin of the transistor Q202.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

Is the C3 the main filter cap?

Just want to confirm that Q202 is a surface mount transistor on the backside of the board.

[budm]

Re: Sony KDL 32L4000 Troubleshooting

Is the C3 the main filter cap?

Just want to confirm that Q202 is a surface mount transistor on the backside of the board.

C3 is the main filter cap.
Q202 is a small SMD Transistor, it is right below INDUCTOR L202.
Make sure not to touch anything with your hands or body while working on the board.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

Make sure not to touch anything with your hands or body while working on the board.

Assuming I can figure that part out I'll let you know what I find.

[budm]

Re: Sony KDL 32L4000 Troubleshooting

BTW, when you look at that SMD Transistor, when you look at it with the two legs pointing down, the pin on the left is the Base, the middle pin (pin on top) is the Collector, the right pin is Emitter.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

OK, for confirmation clarification the Q202 looks like:


C
|
,----'------,
| |
B E

C = 11.86-.89
E = 12.54-.55
B = 11.36-.38

Reading were taken with connector 202 attached to the board as they changed over a fairly wide range otherwise.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

Bud,

I have a replacement board on the way. Do you have any suggestions on replacement? Should I just plug it in and try it or just plug it into AC and test outputs before plugging other connectors in?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

OK, for confirmation clarification the Q202 looks like:


C
|
,----'------,
| |
B E

C = 11.86-.89
E = 12.54-.55
B = 11.36-.38

Reading were taken with connector 202 attached to the board as they changed over a fairly wide range otherwise.

So the transistor is providing 11.86VDC for running VCC of many IC's and also for relay RL1.
the PFC IC ic31 (L6562: https://cdn.badcaps-static.com/pdfs/...1fdeef964c.pdf) has turn-on Voltage range of 11 ~ 13V. So that should be enough for it to run.

[budm]

Re: Sony KDL 32L4000 Troubleshooting

Bud,

I have a replacement board on the way. Do you have any suggestions on replacement? Should I just plug it in and try it or just plug it into AC and test outputs before plugging other connectors in?

It needs logic low for it to come on so you have either GND the PS-ON or just have everything connected up and see if the TV will function or not.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

Got the power board and plugged it in. Powered on, so one issue resolved; however, still would like to investigate the bad board. We know that VCC is present; what is my next step?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

It is a matter of me spending times to look at the schematic to give you step by step to troubleshoot it down to component level. 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.
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?

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

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.

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?

No it doesn't.

[budm]

Re: Sony KDL 32L4000 Troubleshooting

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.



No it doesn't.

So your new board is:
"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. " This does not make sense to me, if you run the power supply board by itself without having it connected to the main board so when you plug in the AC power cord it will be in standby mode which means the Voltage on the PS-ON pin should be at around 4V, it cannot be at 0V because it has pull-up resistor R151 to keep the power supply off BY PULLING PS-ON PIN HIGH when it is not connected to the main board, you can tell if the power supply is really off or not by checking the DCV on the main filter cap, it will be only around 160V.
The 15V, 24V, and the 30V should not be present when you run the power supply board by itself.
If you look at he schematic you will understand why the power supply board will not be on when it is not connected to the main board, the only power supply section that will be running is the 4VSTBY power supply.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

I am not following you.

if you run the power supply board by itself without having it connected to the main board so when you plug in the AC power cord it will be in standby mode which means the Voltage on the PS-ON pin should be at around 4V,

Which is what I said

PS ON is 4.16 in standby and 0 once powered on

The 15V, 24V, and the 30V should not be present when you run the power supply board by itself.

This is what I am seeing. If no connection or if all connected, but power button not pressed there is no 15V, 24V or 30V. Once the power button is pushed then all voltages become available.

Two other observations I noticed. With the new board attached, the standby LED is not lite, but on turning the power on the power LED is lite and the TV does come on.

Secondly, when i disconnect the power cord from the outlet, I continue to get voltage on the 4 VSB connectors for a few minutes (I assume this is the main filter cap discharging); however, on the bad board the voltage is gone in about 15 sec.

[budm]

Re: Sony KDL 32L4000 Troubleshooting

"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.":
Based on your last reply, it is not true then that if the PS-ON is not tied to ground the power supply board WILL come on, so lest forget about it for now. We know you have bad power supply at this point.
So back to the bad power supply board:
1) if you run the power supply board by itself without having it connected to any thing, when you power it up the Relay RL1 will be clicking on and off, correct? If this is true this problem will have to be fix first because some how is able to come on without having the PS-ON grounded, RL1 should never come on without grounding the PS-ON pin.
2) if you run the power supply board by itself without having it connected to any thing and you GND PS-ON pin you do not have > 360VDC on the main cap, correct?