JVC LT-55CF890 backlight on but no image

[notallbad]

Re: JVC LT-55CF890 backlight on but no image

These are the voltage comparisons from the connected panel boards and the spare disconnected from panel board at the LVDS connector.

[dskall]

Re: JVC LT-55CF890 backlight on but no image

If these are voltages with tv on and ldvs connected. You don't seem to have any data coming in from mainboard.

[notallbad]

Re: JVC LT-55CF890 backlight on but no image

ok, well I did get a spare main but symptoms remain the same. Is it poss I have bought a faulty board with the same problem, I suppose its poss.
Shall swap boards and see how voltages compare.

Yeah TV on and lvds connected, though there was no video input but it is a smart tv so should have the main display showing.

[dskall]

Re: JVC LT-55CF890 backlight on but no image

Might press menu and other buttons while you are checking to make sure you are sending out data. The paired lines going into processor should have around 1.2v.

[notallbad]

Re: JVC LT-55CF890 backlight on but no image

Amazingly its just come on, connected to internet and now doing a software update! For better or for worse.

[dskall]

Re: JVC LT-55CF890 backlight on but no image

TaDa.

[notallbad]

Re: JVC LT-55CF890 backlight on but no image

On for a while and done a couple of power cycles and still ok. Shall continue to use for a while before moving it about or removing power completely.

So not entirely sure what the problem was/is but working at the moment.

[dskall]

Re: JVC LT-55CF890 backlight on but no image

You cussed at it didn't you. I found cussing at them can get them to work for no reason.

[vinceroger69]

Re: JVC LT-55CF890 backlight on but no image

On for a while and done a couple of power cycles and still ok. Shall continue to use for a while before moving it about or removing power completely.

So not entirely sure what the problem was/is but working at the moment.

These fire tvs seem to suffer a lot from firmware/mainboard issues not sure what made your set start too turn on etc now but lets hope the latest update has sorted the issues out.

[notallbad]

Re: JVC LT-55CF890 backlight on but no image

sadly not, back to no image again. Lasted for one evening working perfectly even had power completely removed the following day and worked when plugged back in but after being on stby for the day it went back to fault.

I do feel its fw/emmc/mainboard related and think just unlucky getting a faulty 2nd main but if its a common problem might not be so easy getting a reliable main anyway.

[vinceroger69]

Re: JVC LT-55CF890 backlight on but no image

sadly not, back to no image again. Lasted for one evening working perfectly even had power completely removed the following day and worked when plugged back in but after being on stby for the day it went back to fault.

I do feel its fw/emmc/mainboard related and think just unlucky getting a faulty 2nd main but if its a common problem might not be so easy getting a reliable main anyway.

i wonder if jvc will provide you with the firmware for this set it maybe worth a email/phone call.

[notallbad]

Re: JVC LT-55CF890 backlight on but no image

Further details

[menlinks]

Re: JVC LT-55CF890 backlight on but no image

hi,I don't know if it can help you

[notallbad]

Re: JVC LT-55CF890 backlight on but no image

I'm 100% sure its the main processor on the main board, applied pressure to the large heat sink and image now back! Needs reballing I guess but dont have equipment to do that.

[vinceroger69]

Re: JVC LT-55CF890 backlight on but no image

I'm 100% sure its the main processor on the main board, applied pressure to the large heat sink and image now back! Needs reballing I guess but dont have equipment to do that.

is this on your replacement board?

[notallbad]

Re: JVC LT-55CF890 backlight on but no image

no, on the original board.
the replacement board I bought has the same symptoms (no image) but unable to get it to show an image by applying pressure, perhaps too far gone.

I do have another board on its way, fingers crossed though suspect this is going to be a common fault on these boards.

[notallbad]

Re: JVC LT-55CF890 backlight on but no image

For info/ref

14v & 0.02v on this cap

[cheeky2]

Re: JVC LT-55CF890 backlight on but no image

Just make sure your main board is 23587576 otherwise you will inevitably have issues with it (assuming that this is the original main board from your TV that is pictured).

[notallbad]

Re: JVC LT-55CF890 backlight on but no image

the 1st replacement board was the same and did get something change on the screen when applying pressure but not an image.

[notallbad]

Re: JVC LT-55CF890 backlight on but no image

For info/ref.

VSS1 -7.3v
VSS2 -14v

diode fluctuating 8.5v and steady -14v

12.3v on that top cap next to the 4 test points