JVC LT-42TG30J no sign of life at all

[Andyd1970]

Hi Guy,

I have a JVC LT-42TG30J, if you add power to it and touch the "on" switch on front panel you get a tone from touching the "on" but no sign of life at all.

Am I right I need to check for the 5V standby voltage?

[Andyd1970]

Re: JVC LT-42TG30J no sign of life at all

ops!! Forgot the pictures The PSU is a vestel 17PW82-3

[tom66]

Re: JVC LT-42TG30J no sign of life at all

This is probably a main board issue as you will not get a beep without 5V but worth checking PSU voltages anyway

[Andyd1970]

Re: JVC LT-42TG30J no sign of life at all

Hi Tom,

Can you help with expected voltages on particular pins on the PSU please.

[Andyd1970]

Re: JVC LT-42TG30J no sign of life at all

The PSU is:

Vestel 17PW82-3

[tom66]

Re: JVC LT-42TG30J no sign of life at all

Don't have a schematic so you'll have to wing it. Usually looking for 3.3V/5V/12V.

[OracsRevenge]

Re: JVC LT-42TG30J no sign of life at all

Hi,

I have the same model TV, did you ever find a fix for yours?

Same symptoms for me, I have the PSU and main board circuit diagram and went through the Standby and run voltages, all ok. PSU seems fine, no bulging caps. disconnected the PSU cable and jumpered it so I could run the PSU and jumper the backlight on, all tests ok.

I bought a main board from Ebay and it didn't cure the issue, but ...

It has a different fault now, where before the touch panel buttons beeped and there was no backlight showing or standby led, now, I can turn the TV on and off via the remote and the backlight now glows, nothing showing on the screen and still no standby led.

There are no LEDs showing on the TV to indicate on/off/standby (not sure if the processor turns this led on and off though) but the touch panel standby button seems to work ok.

To determine if the main board is working and its a problem with the panel/tcon/cable, I tried to boost up the volume to full, change input source via remote, etc but nothing other than a very low hiss from the speakers. (assuming this is just the audio amp minimum hiss)

As this board does something different to the previous board, can I assume the new board is DOA?

The seller says its from the same model of TV, but it has a slightly different part number (physically looks the same) I am assuming any difference would be minor.

Although the PSU run voltages, 3.3, 5, 12, 24 all check out fine, could there be some other PSU issue with control lines, etc that would stop the main board booting?

Finally, I see a lot of mention around resetting JVC TV's using a combination of button holds whilst power-cycling. This doesn't seem to work for the touch sensitive keyboard (has no separate menu button). Is there any way to force the main board to reset, or to upload new software via USB. The service manual says you can via SUB, but can't find the firmware anywhere on the JVC site or the net.

Any help gratefully received.

Thanks

[OracsRevenge]

Re: JVC LT-42TG30J no sign of life at all

P.s.

PSU is a vestel 17PW26-5
Main Board is a Vestel 17MB70-5P

Thanks

[nomoresonys]

Re: JVC LT-42TG30J no sign of life at all

try putting the number on the white sticker of the mainboard you bought into shop jimmy n see if it says it matches your panel, if you have trouble just post the mainboard number here, and I'll help.

[OracsRevenge]

Re: JVC LT-42TG30J no sign of life at all

Thanks for the reply, the white sticker details on the old and new boards are below

Old
10076189 23041760 8 42"
26848955 LGEWUN-SCB1 GB
V11100_MB70(JVC)


New
10076189 23041760 423 42"
26875102 LGEWUN-SCB1 GB
V11131_MB70(JVC)


I couldn't find part number matches on Shop Jimmy unfortunately.

I am hoping that because there is no standby led and no static volume increase from the speakers, the remote is working to switch the backlight on/off and the touch keyboard is working (old main board did nothing at all) that the new main board is DOA and I can get it replaced.

[nomoresonys]

Re: JVC LT-42TG30J no sign of life at all

kind of hard to find this board seems like, what is your panel number should be on the back chassis?

[nomoresonys]

Re: JVC LT-42TG30J no sign of life at all

is this your panel number? LC420WUN-SCB1 (PL), see if these numbers match, the price is way too high, just trying to see if numbers are right. http://www.chsinteractive.co.uk/elec...60-jvc-etc.htm

[nomoresonys]

Re: JVC LT-42TG30J no sign of life at all

Thanks for the reply, the white sticker details on the old and new boards are below

Old
10076189 23041760 8 42"
26848955 LGEWUN-SCB1 GB
V11100_MB70(JVC)


New
10076189 23041760 423 42"
26875102 LGEWUN-SCB1 GB
V11131_MB70(JVC)


I couldn't find part number matches on Shop Jimmy unfortunately.

I am hoping that because there is no standby led and no static volume increase from the speakers, the remote is working to switch the backlight on/off and the touch keyboard is working (old main board did nothing at all) that the new main board is DOA and I can get it replaced.

if your standby voltage isnt there, its more likely a power supply issue, your mainboard may be ok.

[nomoresonys]

Re: JVC LT-42TG30J no sign of life at all

do you have a digital multimeter?

[OracsRevenge]

Re: JVC LT-42TG30J no sign of life at all

Hi, yes I checked all the standby and run voltages, all are fine. It's just the Standby led that doesn't come on. I guessed that as blinks via cpu control, if the cpu was not booting then the led may not work too.

The code you mentioned above does look like the panel is an LG I can't find a separate sticker on the chassis.


Thanks

[nomoresonys]

Re: JVC LT-42TG30J no sign of life at all

seems to be pointing to mainboard issue, its strange your stndby light doesnt come on, I think I read somewhere that a bad mainboard could possibly cause it not to come on.

[OracsRevenge]

Re: JVC LT-42TG30J no sign of life at all

Thanks, I will speak to the vendor and request a replacement.

[Alastair E]

Re: JVC LT-42TG30J no sign of life at all

No surprise you wont find a VESTEL part on shop-jimmy, They are mainly European sets. I dont think any Vestel junk was sold in USA.

They did sell in Iceland though....

[tom66]

Re: JVC LT-42TG30J no sign of life at all

Vestel PSUs have designs to accept 100-270V AC in, but AFAIK they haven't sold any models to the US yet (consider it a blessing!)

[Alastair E]

Re: JVC LT-42TG30J no sign of life at all

Vestel PSUs have designs to accept 100-270V AC in, but AFAIK they haven't sold any models to the US yet (consider it a blessing!)

Aye!--They dont know how lucky they are!