Another Sanyo DP42848 Good Sound/No Picture

[johnboy1313]

Re: Another Sanyo DP42848 Good Sound/No Picture

Any idea where I might find that number?

Also, the only two success stories I've seen with this problem on this model of TV both said that they changed the Main Board and got the TV to work again. Could I be barking up the wrong tree? Are there some tests I can run on the main board to see if it's the culprit?

[tom66]

Re: Another Sanyo DP42848 Good Sound/No Picture

LCD panel number will be on the back of the display panel itself (not on the casing of the TV.) E.g. "CHI-MEI OPTOELECTRONICS CM42XXXXXX MADE IN TAIWAN"

[johnboy1313]

Re: Another Sanyo DP42848 Good Sound/No Picture

I used the link in your signature to find the service manual for this TV. I found these two pages to be interesting. In the first picture, there's a note that says that the TV "If power failure is detected 3 times in 15 minutes, the set will enter the standby mode and cannot be switched on" until it is unplugged and allowed to set. To test if this was what was happening, I purposely powered the TV on and off three times in a row. On the 4th time, it powered on and shut the screen off again. I thought I was onto something, but apparently not.

In both the first pic and the second pic, the diagrams show pin 18 on IC800 to be "POWER_ON". I see nothing in the manual that says that I should be able to probe for power at that pin. When I look at the control port function list for IC800, I see several pins that say High/Low. For instance, pin 17 is LED control for the indicator light. It says under the description, "LED control Power On:High, Standby:Low" What are they referring to with High and Low? Are there to be two different voltages at that pin or am I misunderstanding something?

[johnboy1313]

Re: Another Sanyo DP42848 Good Sound/No Picture

So, I've had a breakthrough of sorts. I'm just not sure what it means, if it means anything at all. In the bottom picture in the post above. In the lower left corner is a connection labeled "K8L". Currently, with that connected when the power is turned on, there is a click followed by a ~2 second pause until the back lights come on. They stay on for a second or two and then turn off. With K8L disconnected, the lamps will light immediately at power on and stay on for ~15 seconds, with a picture. With the lights on, I see no streaks across the screen, which if there were streak(s), I would assume would mean a bad CCFL. Am I right?



With that said, at connection CN4 on the lower picture above, I'm getting 24VDC at both the power supply and the inverter. With K8L connected, I get ~3.5VDC at both the main board and the inverter. The 24V is correct. I don't know if the 3.5V is correct or not.

Does any of this mean anything?

[budm]

Re: Another Sanyo DP42848 Good Sound/No Picture

The 3.5V reading on the inverter board pin is probably the BL_ON signal which is generated by the main board, most inverter board will use voltage>3v to turn on the inverter, <1v for OFF. The spec of the LCD will tell exacly what it should be.

[johnboy1313]

Re: Another Sanyo DP42848 Good Sound/No Picture

I see no streaks across the screen, which if there were streak(s), I would assume would mean a bad CCFL. Am I right?

I see the streaks now. Not enough experience to know what to look for.



I stand corrected. Two bad bulbs

[budm]

Re: Another Sanyo DP42848 Good Sound/No Picture

Well, john, you are pretty good for beginner and be able to remove the LCD panel without damaging it.
I wonder if it has a bunch of small blue ballast caps for each lamps like this:
http://s807.photobucket.com/albums/y...nt%20FLX-3210/
Great job locating the exact problem.

[johnboy1313]

Re: Another Sanyo DP42848 Good Sound/No Picture

Well, john, you are pretty good for beginner and be able to remove the LCD panel without damaging it.
I wonder if it has a bunch of small blue ballast caps for each lamps like this:
http://s807.photobucket.com/albums/y...nt%20FLX-3210/
Great job locating the exact problem.

I'm not through the woods yet. The lamps look like they have a lead electrode on each end and from what I can tell by looking online, they're 950mm X 3.5mm.



Both ends are identical.

[johnboy1313]

Re: Another Sanyo DP42848 Good Sound/No Picture

What type of bulbs are those anyway? So far, the only ones I can find have a short thin electrode sticking out of the ends.

[johnboy1313]

Re: Another Sanyo DP42848 Good Sound/No Picture



From the back of the LCD panel.

[budm]

Re: Another Sanyo DP42848 Good Sound/No Picture

The lamps do not look like it has any blackened at the ends which is typical when lamps are worn out.
It they are not socketed? If they are, then you can move it to other position.
I think some one here had done some lamp replacement on this type of lamp setup, hopefully they will chime in.
Spec sheet:
By the way, this is a great site for LCD panel info:
http://www.gblcd.com/data_center_lcd_panels.htm

[johnboy1313]

Re: Another Sanyo DP42848 Good Sound/No Picture

It's hard to see in the picture but the fifth lamp up is blackened at one of the supports about a third of the way in from the right. The bottom lamp is not blackened or cracked anywhere that I can see.

[johnboy1313]

Re: Another Sanyo DP42848 Good Sound/No Picture

Found an ad on Craigslist for a guy that buys broken flat screens. I gave him a call and he said he was out of the business. He wasn't buying anymore TV's. That's fine, I just need some parts. Turned out the only parts he had left were the ones I needed. He sold me three bulbs, the two I needed and an extra for $25. It's been on for a half hour. No buzzing, no popping, no flickering. Thank you Craigslist, thank you Tom66, and thank you Budm. If you look close, you can tell which ones I replaced. They were a little shorter than the others, but no big deal.

[budm]

Re: Another Sanyo DP42848 Good Sound/No Picture

You are so lucky.
By the way, can I post your pictures in my photobucket so it may help other people as well? Thanks.

[tom66]

Re: Another Sanyo DP42848 Good Sound/No Picture

Nice fix!

[johnboy1313]

Re: Another Sanyo DP42848 Good Sound/No Picture

bud, post the pics where ever you see fit.

tom, thanks.

[tocold4u2]

Re: Another Sanyo DP42848 Good Sound/No Picture

i hav the same tv doing the same ,, i would like to check the bulbs,,and plug connector..how do you get to the bulbs and or plug?
thanks

[DakotaKid]

Re: Another Sanyo DP42848 Good Sound/No Picture

You can check out another thread here for additional info: https://www.badcaps.net/forum/showthread.php?t=18453
When you take the back off you will see a plug connector pigtail with white plugs and most likely pink and white wires at the left and the right sides that is plugged into the inverter board and panel on each side. Remove the metal shields on each side to get to the inverter boards. The left side master inverter "M" has multiple plug connections from the boards in the TV plus the ribbon connecting it to the slave inverter "S" over on the right side. You can do a neon/small wattage fluorescent tube test as described in the "2 seconds to black" guide to find out if the inverters are good. My slave inverter was bad. I never did open my panel to see if there was a bulb blown but I'd guess there might be a bad or going bad bulb that possibly caused the inverter to go. You'd be very fortunate to only have bad bulbs like johnboy did. To get to the bulbs you have to disassemble the entire TV and remove the LCD panel and filter sheets. This TV actually comes apart pretty easy by removing the black plastic frame that has the boards attached to it. Then keep removing screws on the panel till you get to the tubes. Good luck.

[tocold4u2]

Re: Another Sanyo DP42848 Good Sound/No Picture

ok thanks....the left side i hear a buzzing noise when the backlight comes on,,, just like his post or yours,,o,i forget which one it was. was thinking maybe just a loose wire,,,idk.

[tocold4u2]

Re: Another Sanyo DP42848 Good Sound/No Picture

my prolbem is ,,when you get it down to almost the bulbs how to get it to power on to c if the bulbs are bad or not?? i had it where i could peek in from the bottom corner, and i did see two bulbs that were black/greyish in the middle of the bulbs,,,,would those two bulbs be bad??