Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
With the LEDs on:
The anode (red wire) for the LEDs was at 86V with respect to chassis ground
The cathodes (blue wires) were at 10.8V with respect to chassis ground
Sorry I didn't record all of the other vbltages again....
lamlash
Member
Last Activity: 09-30-2019, 06:40 AM
Joined: 08-05-2019
Location: newcastle
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
Hi guys, the TV is now fixed. I stripped it apart again and refitted the polariser/diffuser sheets more carefully. Picture is perfect now.
I can't say 100% what the fix was. The reset procedure (vol- / AV / power button) eventually did it but that only worked after stripping the whole TV to pieces and re-assembling. Maybe there was a bad connection on the LED strips, maybe the freezing of the EEPROM was effective and just needed the reset procedure too.
When I get time later I'll post up a...Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
Thanks, I can't find the relevant page in the service mode that shows if there are lamp errors.
Is it possible the LEDs are all working but I somehow mis-assembled the panel? I've had the entire TV in pieces!Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
Wait - I have it working... kind of. I just tried the reset procedure one more time (power plug out, hold down vol-, AV and power button then plug in power again). And it works.
But now I have a screen that is a little dark on the left hand side, like the left hand strip of LEDs is not as bright. Otherwise working perfectly.Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
OK thank you very much for your help. I've reached the end of troubleshooting now and will tell my friend that we can take a chance on a Board A with the exact same part number. There are a few on ebay which are claimed to be tested and working for around £30. Or he can buy a new TV!
Thanks againLeave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
Can you let me know if the following is correct?
1. The TV won't come on because BL_SOS is at 3.3V (asserted)
2. The BL_SOS signal originates in the main board (Board A)
3. The BL_SOS signal goes into to the power board at connector P2 then out of P4 and into the LED driver
4. The LED driver inhibits the voltage booster circuit so the anode only has 24V on it and the PWM signals for the FETs for the cathodes are not switched
So my focus of investigation should be Board...Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
Hi, the EEPROM freeze didn't work. I froze IC8901 and IC8902 then powered the TV up. No change : no red standby LED, about 44 fast flashes of the green LED then nothing once a key is pressed on TV or remote.Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
Thanks I will try it tonightLeave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
I'm not sure if you're serious!
About 30 years ago there was an urban myth that you could wipe the security code from a car radio by putting it in the freezer. I think it was a wind up so I'm sceptical about this too!Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
? Freeze it ? Put the main board in the freezer? Are you kidding?&Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
On my TV those anode wires for the LEDs are red. They are only at 24V DC which is nowhere near enough voltage for the LED strips which seem to need at least 70V per strip from what I can tell. I will have a look at the schematic for the LED driver board later today....Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
OK. So here's the readings:
P2
1. 5.75V
2. 5.75V
3. 0V
4. 2.1V (seems to be falling)
5. 2V (falling)
6. 2V (falling)
7. 0V
8. 0V
9. 5.7V
10. 2.7V (falling)
11. 2.8V (falling)
12. 5V (falling)
13. 0V
14. 0V
15. 0V
16. 0V
P4
pin 4 is at 3.2V, the others are 0VLeave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
Can't see anything like that on the back of the board. Photos attached....Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
I'm not sure I understand what you mean. Here's a picture of the connectors on the power board....Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
I tried this on my DVM. They all read about 0.740V on diode mode but they didn't light up at all. I'm sure all the LEDs are OK because they all have the exact same behaviour. I think I need to look at the LED driver PCB in more detail....Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
I need to learn more about this - could you send me a link to that post please?...Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
I tried this and the blue wires all seem to be at a floating voltage. There isn't any distinct change in the meter reading when the power is switched on. I did this with the LED panels wired up but the TV screen panel disconnected. Everything else was connected....Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
Here's the LED driver.
Returning to the LED strips themselves, my bench top power supply only goes up to about 30V so I cannot test each string of 14 LEDs using 42V limited to 200mA. However I have tested each individual LED and they all work but the IV characteristic of the individual LEDs was very strange. I had to bias them with at least 5.1V forward voltage before they light up individually (with the power supply leads directly across each LED one at a time). The the current has to be limited to...Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
Thanks.
Each strip has 42 LEDs. The circuit arrangement is 3 parallel sets of 14 series-connected LEDs.
When you say 200mA, is that for the complete strip (so each LED would have a drive current of 66mA)? I'll got and try it!Leave a comment:
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Re: Panasonic Viera TX-L32E3B won't power up, green LED flashing
OK thanks. I have dismantled too many parts to test the LED strips using the TV power supply. Do you know approximately what the I-V operating point of each LED should be? I could connect each LED to a current limited bench top power supply. Does 3V limited to 10mA seem reasonable to light up each LED without damaging it?
Here's a photo of the connector - I can't see any problem with them....Leave a comment:
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