Sanyo DP46480 2s to black

[tom66]

Re: Sanyo DP46480 2s to black

Can someone confirm what I expect, or correct me?
1. On top is the LCD panel. It's glass and has to be supported evenly or it's own weight will crack it. It's not rigid. The back is more delicate then the front, I plan to lay it face down on a table with some bubble wrap on it.

It's reasonably flexible and you can bend it slightly without damaging it, but it's not recommended. I would say you should lay it on some cushions or a spare duvet. Also be extremely careful with the driver flex attached to the panel such that you don't damage these or the picture will have artefacts on it. (Usually black lines.)

2. Next is some type of light diffuser. I don't know what to expect here, is it multiple sheets? Can I scratch it? The lcdparts website shows them just lifting it up and leaning it behind it. That is my plan, it must be fairly rigid?

It's both . There are some thin diffuser sheets (from two to five, depending on the LCD quality.) Then there is usually a rigid thick plastic light guide plate. Neither are particularly easy to damage, as the plastic is difficult to scratch. Avoid getting marks on them from fingerprints though - this would leave a mark on the picture (you can clean them with a damp cloth.)

3. Then I have reached the bulbs and I have to find a way to test them!

Simply turn on the TV and the bad bulb(s) will be easily visible; it/they will either not light or only partially light.

[CommTechRepair]

Re: Sanyo DP46480 2s to black

It was certainly a bad tube! It was cracked good, but all the other bulbs turned on just fine. Thank you for your help. Now I have to find a compatible tube, hopefully be back in business.

[killian6pk]

Re: Sanyo DP46480 2s to black

Go back to the LCD site you just looked at for the transformer info. Give them the name and model number of the tv and they should be able to get you the correct lamp.

[selldoor]

Re: Sanyo DP46480 2s to black

It was certainly a bad tube! It was cracked good, but all the other bulbs turned on just fine. Thank you for your help. Now I have to find a compatible tube, hopefully be back in business.

People have also had good service from ccflwarehouse.com
they also have an ebay site plazmo industries

[killian6pk]

Re: Sanyo DP46480 2s to black

It was certainly a bad tube! It was cracked good, but all the other bulbs turned on just fine. Thank you for your help. Now I have to find a compatible tube, hopefully be back in business.

I have changed quite a few lamps in monitors lately and a warning is in order. The lamps are very fragile. Make sure especially with the one you will be dealing with to keep is supported along its length, just because they are so long. Also don't put any undue pressure on them while getting them seated. I am sure these are very expensive so you don't want to have to buy another.

[CommTechRepair]

Re: Sanyo DP46480 2s to black

I put the new bulb in and it went in nice and smooth. It unfortunately didn't solve the problem. I set up the power supply and main system board to test it out before putting the panel back on. Every light comes on this time, they all look the same brightness but it then turns off.

Could another bulb be bad but still turn on like it worked?

[selldoor]

Re: Sanyo DP46480 2s to black

I dont know that you ever bottomed out the inverter transformer test.
Not many pins so do it the long way - power off for 5minutes, Meter on 2000 ohms
number the pins in your head or write it down and measure
1>2 1>3 1>4 1>5 and so on
then 2>3 2>4 2>5 and so on
then 3>4 3>5 and so on until you have covered them all One pair should be high ohms when you find that pair check it on each transformer and post the result

[CommTechRepair]

Re: Sanyo DP46480 2s to black

I took one of the transformers off to see which pins had which windings. The high ohm windings where as follows:

1. 800
2. 804
3. 806
4. 805
5. 808
6. 798
7. 798
8. 807
9. 802
10. 799
11. 805
12. 796

I also measured the lower ohm winding and found I measured 1/2ohm on all of them. I tried to test for any shorts between the primary and secondary and it measured 4.2kOhm in circuit. They look in parallel so I shorted out a primary/secondary winding in another circuit with a wire and it them measured 0 Ohm. That seems to tell me theres no problem with primary to secondary shorts.

[CommTechRepair]

Re: Sanyo DP46480 2s to black

I've noticed recently someone else who owned the TV before me replaced the capacitors in the power supply. You can tell the capacitors are all Nichicon and Rubycon now with leads that are a little long, and solder work that looks a bit off.

Watching the voltage from the power supply to the inverter board on the scope I can see a 4% voltage drop. It sits at 24V and when the backlights turn on the voltage drops 1V until the lights blink off (under a second on-time now, a lot fast it seems since I took the front LCD panel off). Is that voltage drop enough to set off a protection circuit?

[selldoor]

Re: Sanyo DP46480 2s to black

It would be useful for others reading in future if you could marke up the transformer showing te secondary pins.
In order to try and troubleshoot this we need to be able to see the boards so can you take pictures of both sides of the power supply main board and inverter board. Need them to be clear so we can see the board numbers.

[CommTechRepair]

Re: Sanyo DP46480 2s to black

It is a AUO 19.46T03.020 Backlight Inverter, the part can also be seen here:

http://www.shopjimmy.com/auo-19-46t0...t-inverter.htm

[billansor]

Re: Sanyo DP46480 2s to black

Hi
It has been a while since I have posted and during that time have learned a great deal..... One of the sets that have been a biggie in the learning curve has been the Sanyo's

In this series Sanyo and for all others there are a current sensing line that lets the main board (micro) know if too much current is being pulled.... Having said that, there is also a similar current sensing line that is in the inverter board too.. Multiple redundancies...

This Sanyo has numerous issues with bad bulbs and also bulbs that are weakening. Since you have the shell opened and if you are able to separate the panel and diffusers so that you can see the bulbs light up, you should be able to get that there are other bulbs that are in rough shape or pinkish...

The other thing to be aware of while someone has replaced the caps, it probably would not hurt to dig a print up to make sure that the caps are the right ones....

As far as the inverter transformers go, you do not want to see much of a variation between each...

You do not want to see much variation in the secondaries of each transformer... An example would be.... lets say each transformer measures between 390 to 405.... But you came across one that was 375... I would consider that one bad.... Even perhaps 380..

My two bits....

Bill

[CommTechRepair]

Re: Sanyo DP46480 2s to black

Thanks Bill,

I tried to look for bad bulbs and while doing so the power supply stopped working. Not sure if it's a new hurdle or the original problem showing itself.

Right before the power supply stopped working I saw one bulb phase out before the rest shutdown. Made a cool effect. I don't think the power plug was secured well from the supply to the inverter. Other then that quirk it didn't look like any were blue, but I can't say for certain.

It intermittently works, I looked at it this morning (sat for 10 hours) and all the lights came on and then shutdown like it has been. After two tries it stops working all together again.

I took the power supply out and supplied it 3.3V to the PS_ON pin from the system board. I can hear the relay click but there's no output voltage. The voltage stops right before the FET's that drive the transformer, which makes sense because nothing is driving the gate. I took the FET's out and tested them with a power supply and multimeter. They had a 10V on voltage but they worked fine.

I suspect it could be the IC driving the FET's. It is an SSC9510s, and it connects directly to the FET's. The only suppliers I have found are in China. Does anyone know where I might find one that is in the United States so I don't have to wait 2 weeks for it to arrive?

[CommTechRepair]

Re: Sanyo DP46480 2s to black

Just as an update I found the relay ( LKS1AF-12V ) was pulling down the 12V S-VCC line. The coil resistance was 278 Ohms, where the specification calls for 576 Ohms +/- 10%. Don't have one on hand but I'm hoping it will be the main problem.

[CommTechRepair]

Re: Sanyo DP46480 2s to black

I still have the 2s to black problem. Since I've last posted I had one transformer start smoking on me. I pulled the transformer and measured it's secondary resistance and it was only 2% off, I don't understand what was smoking. I replaced all the transformers that were greater then 1% of the average. That didn't solve anything.

I adjusted the timer capacitor on the CCFL driver IC and that allowed me to keep my bulbs running for longer. Instead of less then a second it will run for about 20 seconds. Now I can look for something visually wrong with the bulbs but I see nothing. They ignite fine everytime, but the circuit detects a problem. It must be the bulbs? What else can I check?

[budm]

Re: Sanyo DP46480 2s to black

Are the small blue ballast caps OK? Check for leakage resistance.

[CommTechRepair]

Re: Sanyo DP46480 2s to black

Yes one for each transformer.

[budm]

Re: Sanyo DP46480 2s to black

Thsoe caps limit the current flow through the lamps, if they have resistance leakge, the lamp will draw a lot of current.

[CommTechRepair]

Re: Sanyo DP46480 2s to black

I checked the caps with an ESR meter, and didn't get any reading which I take to be good. Not sure if I can make that measurement with it connected to the secondary of the transformer though. I remember reading that my meter does not like inductances.

I tried it also with a multimeter. I'm not sure exactly what I'm measuring. I put ito n ohms setting and measure the cap and after I hold it there long enough to put some charge into the cap I get these readings in Kohm:

84.4
65.5
60.1
68.2
65.3
65.3
60.3
65
65.1
64.9
93.7
65.5

Two are high, 84.4 and 93.7 but that isn't leakage through the cap if it is higher? Plus can it be possible to know what to expect with that kind of measurement?

[CommTechRepair]

Re: Sanyo DP46480 2s to black

I have a second inverter board I compared my values too. The numbers are consistent. It's back to just the bulbs pulling too much current then?