Sanyo DP 42848 No picture

[topfli8979]

Have a Sanyo DP42848 lcd, upon intial plug in, get picture then it shuts down. Also known as "2-seconds to black". No bulged caps on ps,inverters,or main.
Did find a couple shorted mini 3 leg fet's that show short, ONLY when the tv is plugged in but not powered on. When unplugged from the wall NO SHORT.
Any input?

[topfli8979]

Re: Sanyo DP 42848 No picture

Alll of the voltages are fine,24,12,+5 standby, all steady even after tv loses picture.

[tom66]

Re: Sanyo DP 42848 No picture

Check BLON is steady.
Pictures would also be appreciated.

[johnboy1313]

Re: Sanyo DP 42848 No picture

I had the same problem with the same model. Turned out to be two burned out ccfl bulbs. Check my posts.

[topfli8979]

Re: Sanyo DP 42848 No picture

Yeah I have read through every post for sanyo lcd. I dont know what's going on. Bl_SW goes to 3volts on power up then drops out to millivolts when screen goes to dark.

[tom66]

Re: Sanyo DP 42848 No picture

Main board failure.

[topfli8979]

Re: Sanyo DP 42848 No picture

Ok, was thinking that also. I do have a sanyo dp46841 with a cracked screen. Working main board, identical to the 42 main in every way except for the k5l backlight connector is not on the 46 board, but has a spot for it, could I just solder the connector from the 42 onto the 46 board?

[tom66]

Re: Sanyo DP 42848 No picture

Possibly. There is the chance of panel incompatibility between the boards, but it's likely to work.

[johnboy1313]

Re: Sanyo DP 42848 No picture

On my set, with the connector circled in the pic below unplugged from the main board, the backlights would light for ~15 seconds rather than ~2 with the connector plugged in. If this is the case, I'd still suspect burnt out bulbs. If I remember correctly, my BL_SW voltage dropped out as well when the backlights shut off.

Note, I'm pretty sure this was the connector, it ran to the master inverter. I do remember that it was only two wires and this is the only two wire connector that I see in my pictures. If you could post a clear picture of the back of your TV with the cover off, it might jog my memory.

[johnboy1313]

Re: Sanyo DP 42848 No picture

OK, I guess I should have read my own thread a little closer.

From my thread...
"With K8L disconnected, the lamps will light immediately at power on and stay on for ~15 seconds, with a picture."

So, if that connector is labeled K8L, it is the correct one. If not, look for K8L and disconnect it.

[topfli8979]

Re: Sanyo DP 42848 No picture

I saw that in your thread last night, and disconnected kl8. All it did was come on instantly and shutoff just as fast as with it connected.

[topfli8979]

Re: Sanyo DP 42848 No picture

I tried changing k8l connector to a spare identical board I had from a sanyo 46 lcd, the tv would not even recognize it. Would not do anything. So from there I went to disassemble the panel and have a look at the ccfl's. They are all intact and working correctly, no burnt or broken bulbs.

[kevinm34232]

Re: Sanyo DP 42848 No picture

Tom could he jump BL_SW with another source and see if the backlight stays on? Could that be a permanent fix?

[tom66]

Re: Sanyo DP 42848 No picture

It might keep the backlight on, but if the main board is switching off the backlight, chance is everything else is too, i.e. video outputs and/or power supply.

[topfli8979]

Re: Sanyo DP 42848 No picture

I am gonna keep searching on the main board for the short, these boards are $100 online. Sanyo Tv not worth that kind of money for board repair. Will let ya know if I find anything.

[topfli8979]

Re: Sanyo DP 42848 No picture

I wanted to share this, when I was removing the front lcd panel to look at the ccfl's. The backlight seemed to stay on longer with the panel connected to t-con. Almost 15 seconds. As soon as I hooked everything back up, went back to 2 seconds to dark.

[budm]

Re: Sanyo DP 42848 No picture

It may use the error signal from T-CON board to tell the unit to shutdown. Do you have the LCD PANEL model number as printed on the panel? Also monitor the voltage on the T-CON board fuse to see what you have when you turn on the TV and after it goes into shutdown.

[topfli8979]

Re: Sanyo DP 42848 No picture

14.88 volts, same with backlight on and after backlight shutdown.

[budm]

Re: Sanyo DP 42848 No picture

That seems too high, mot upper limit for T-CON is about 15V at most. Is your meter batteries good? LCD panel spec will tell us what the voltage should be for this LCD panel.

[topfli8979]

Re: Sanyo DP 42848 No picture

Lcd panel model # T420HW01 V-2.

There is not a sticker specifying what the voltages should be.