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?
CommTechRepair
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Last Activity: 05-18-2013, 03:39 AM
Joined: 08-03-2012
Location: Milford
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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...Leave a comment:
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Re: Sanyo DP46480 2s to black
Yes one for each transformer.Leave a comment:
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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...Leave a comment:
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Re: Dell SE198WFPf - Backlights go off after 2 seconds
This thread came up for my search on a datasheet for a OZ9937GN. A 9937 is not the same as a OZ9938. I couldn't find a datasheet, but the brochure I've attached includes application notes with the pin-outs....Leave a comment:
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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.Leave a comment:
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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...Leave a comment:
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Re: Sanyo DP46480 2s to black
It is a AUO 19.46T03.020 Backlight Inverter, the part can also be seen here:
[url]http://www.shopjimmy.com/auo-19-46t03-020-backlight-inverter.htm[/url]Re: Sanyo DP46480 2s to black<br /> ...rter.htm[/url]...Leave a comment:
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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...Leave a comment:
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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:[LIST=1][*]800[*]804[*]806[*]805[*]808[*]798[*]798[*]807[*]802[*]799[*]805[*]796[/LIST]
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...Leave a comment:
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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?Leave a comment:
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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....Leave a comment:
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Re: Sanyo DP46480 2s to black
I'm attempting to take the LCD panel off so that I can get access to the CCFL tubes. I don't know anything past what I've learned here:
[url]http://www.lcdparts.net/howto/troubleshooting/LCDTVCCFL.aspx[/url]
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.
2. Next is some type of light diffuser....Leave a comment:
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Re: Sanyo DP46480 2s to black
I don't know exactly which pins lead to the secondary winding. I uploaded a picture of the pins I measured. The measurements were consistent with each other and with a second inverter board I have of the same part. From 0.81ohms to 0.82ohms.
The two smaller pins I suspect is the primary winding just measured a short, I don't have a meter sensitive enough to measure it....Leave a comment:
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Re: Sanyo DP46480 2s to black
I don't think measuring EMF with the scope will tell me if a bulb is bad. It would tell me the high voltage exists on the transformer, but nothing about the current.
Are CCFL like fluorescent lamps I have above me. They start at a very high voltage but that drop to 25V from then on. Maybe they fail when the voltage drops, instead of my assumption the circuit is gone into a protection mode.Leave a comment:
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Re: Sanyo DP46480 2s to black
On that train of thought the unused pins are silk screened onto the inverter as IPWM, and DET.
Edit: I have a service manual for a similar model using the same system board I found in another post on the forum. The pins are definitely not used.Last edited by CommTechRepair; 08-08-2012, 03:23 PM.Leave a comment:
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Re: Sanyo DP46480 2s to black
That trick worked very well. I had to go through each one with a new power cycle since the inverter shuts down pretty quick. I had two questionable waves, not much smaller but by half. After I checked all of them I went back and retested them made sure my distance was consistent and they were fine too. So if the transformer putting out a wave at a consistent level at the same distance is a good indicated that the bulbs are working then they are all good!
I am very stumped! One thing I'm confused about is I expected there to be feedback...Leave a comment:
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Re: Sanyo DP46480 2s to black
Any hints on how to get to them? I could put some nonconductor over the pads when I push the inverter into place so that it doesn't light that set, but will that cause harm being unbalanced?
[URL="https://www.badcaps.net/forum/attachment.php?attachmentid=44793&stc=1&d=1344458148"]Picture of CCFL connections[/URL]
[I]Sorry I don't know how to link to images without them loading inline[/I]Re: Sanyo DP46480 2s to black
Any hints on how to get to them? I could put some nonconductor over the...Leave a comment:
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Re: Sanyo DP46480 2s to black
It's a large 46" TV, so I don't have any tubes. I don't know of a way to test it in the short amount of time until it shuts down. It must be the same idea however, a bad CCFL tube will turn on even if it's failing?Leave a comment:
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Sanyo DP46480 2s to black
I have a Sanyo DP46480 that when you turn it on the backlights come on after a few seconds, stay on momentarily then shut off. The TV continues to run with sound in the background and I can see video if I hold a flashlight up to it.
So far I've put an oscilloscope on the power connectors from the power supply board to the main system board. There was no ripple and voltages where good. I compared it to the expected voltages that are silk screened on the board.
The power connector from the power supply to the backlight inverter board has 9 pins, 4 marked ground, 4 marked...Last edited by CommTechRepair; 08-08-2012, 01:45 PM.
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