Panasonic TX-L32U3B will not power up

[Bing]

I have a 32" panasonic TX-L32U3B LCD tv that i have that i am a bit stuck on,
when tv is plugged in and turned on all you get is green led on front on, when i first tried it did briefley come only for few seconds, the psu looks ok there is no legend for the rails but voltages are as follows
0 v
0 v
0 v
0 v
3.1 v
0 v
0 v
5.8 v
2.8 v
0 v
16.1 v
16.1 v
16.1 v
0 v
5.8 v

when i tried to power up tv with the psu output removed i did not even get green light on.
Any help on this would be great thanks for reading.

[Bing]

Re: Panasonic TX-L32U3B will not power up

Here are images of main and power pcbs

[Bing]

Re: Panasonic TX-L32U3B will not power up

Better image of main board

[nomoresonys]

Re: Panasonic TX-L32U3B will not power up

https://www.youtube.com/watch?v=4v8DcqCNG4A testing power supply.

[nomoresonys]

Re: Panasonic TX-L32U3B will not power up

I have a 32" panasonic TX-L32U3B LCD tv that i have that i am a bit stuck on,
when tv is plugged in and turned on all you get is green led on front on, when i first tried it did briefley come only for few seconds, the psu looks ok there is no legend for the rails but voltages are as follows
0 v
0 v
0 v
0 v
3.1 v
0 v
0 v
5.8 v
2.8 v
0 v
16.1 v
16.1 v
16.1 v
0 v
5.8 v

when i tried to power up tv with the psu output removed i did not even get green light on.
Any help on this would be great thanks for reading.

By this, do you mean you unplugged powersupply from mainboard?

[Bing]

Re: Panasonic TX-L32U3B will not power up

I got the voltages from the main board being plugged into PSU but after I got readings I then disconnected mainboard after just to see if backlight came on.

[nomoresonys]

Re: Panasonic TX-L32U3B will not power up

Thats a tough one, very strange that there are no legends.

[nomoresonys]

Re: Panasonic TX-L32U3B will not power up

With a legend its not to hard to figure out how to jumper the powersupply to try to turn on backlights, I have no clue without a legend tho, might need a schematic.

[nomoresonys]

Re: Panasonic TX-L32U3B will not power up

Guess its also possible that the backlights shoud have come on with mainboard unplugged but something else is wrong.

[budm]

Re: Panasonic TX-L32U3B will not power up

Can I see the pictures of the whole backside of the TV showing all the boards?
I also need the pictures of the TV model number sticker to see if it has chassis number printed on the sticker or not
Chassis LA14?

[Bing]

Re: Panasonic TX-L32U3B will not power up

Here are the images you asked for thanks for replying

[budm]

Re: Panasonic TX-L32U3B will not power up

OK, the chassis is GLP26, so will have to search ELEKTROTANYA to see if they have service info there or not.

[vinceroger69]

Re: Panasonic TX-L32U3B will not power up

service manual may not be exact match but same chassis

[will62]

Re: Panasonic TX-L32U3B will not power up

Also found a schematic for the TNPA5361 board. Note that on the OP's voltage readings, there is 3.1V on the INV_SOS pin. The signal comes from the driver IC's "fail" pin.

[Bing]

Re: Panasonic TX-L32U3B will not power up

Ok that's interesting so does that mean that the fault is with the IC or does inv mean inverter circuit? Is so how would I go about troubleshooting this? Thanks for replying

[will62]

Re: Panasonic TX-L32U3B will not power up

This is from another Panasonic set. The component numbers are probably different, but it gives you an idea of how Panasonic uses the "INV_SOS" signal:


"The INV_ON/OFF command (high) of the MPU, IC8001 of the A board,
enters the P-Board to turn on the inverter circuit. The inverter circuit
produces AC voltages that power the backlight fluorescent lamps . The
output of the inverter, approximately 2Kvp-p is provided to the LCD panel
via the connectors P5, P6, P7 and P8.

To avoid catastrophic failures, when the inverter circuit is defective, the
INV_SOS command is output to IC8001 to trigger the shutdown of the TV."


The INV_SOS signal is coming from the inverter driver IC, so I would say that you have a problem with the inverter or lamps.
I'm trying to locate a datasheet for the IC.

[nomoresonys]

Re: Panasonic TX-L32U3B will not power up

Great info will62 and very well explained.

[will62]

Re: Panasonic TX-L32U3B will not power up

Thanks nomoresonys. I couldn't find a datasheet on the BD9247F. I did look at similar chips from the same chip maker, and it appears that they don't follow a consistent pattern with the "fail" pin. On a BD9240, a low signal on fail is an error. On the BD9244, a low signal is normal. So, not sure if low or high indicates an error with this BD9247F.

Read the linked thread. He also had a high signal on the INV_SOS. He did a reset to resolve it:

https://www.badcaps.net/forum/showthread.php?t=67544

[Bing]

Re: Panasonic TX-L32U3B will not power up

Well I just done a reset same as the they did in the link and TV is now working fine!! Thanks for that much appreciated!

[will62]

Re: Panasonic TX-L32U3B will not power up

Hey, that's great!