Author Topic: tx-42A400b (Read 652 times)

t1412 · « **on:** January 08, 2019,14:04:29 »

hi fella's anyone got service manual for this tv panasonic tx-42A400B, you turn the tv on screen flashes up for second the red standby light flashes slowly backlight working tester with backlight tester at the connections on the psu, psu voltages 5.1v no 3.3 thanks for your time

shaun

Mulja tv repair portal · « **on:** January 08, 2019,14:04:29 »

jordan · « **Reply #1 on:** January 08, 2019,15:23:43 »

https://www.electronica-pt.com/esquema/tv/panasonic-esquemas-tv/panasonic-tx-42a400b-chassis-km25e-32804/

downunder · « **Reply #2 on:** January 09, 2019,03:23:17 »

Hi Shaun,

I take it the red LED is flashing code 1 which is a backlight fault. The LED driver board is usually bullet-proof, unless it's had external interference like fluid spilt on it.

While I'm thankful for the LED tester, it doesn't always reveal a faulty LED string because it a low current device and doesn't duplicate the operating condition of the LEDs (which are usually wound up to maximum brightness). Do you mean the 3.3V is missing?

Some punctuation marks would be helpful. Bruce

Mulja tv repair portal · « **Reply #2 on:** January 09, 2019,03:23:17 »

Turnip · « **Reply #3 on:** January 09, 2019,12:58:21 »

Hi Shaun,

Agree with Bruce, had a similar set where code 1 was the biz, though the edge lights tested OK, in and out of the set.
New led strip from China sorted the code issue, though still can't sort any duff Leds on the old strip - Chris.

t1412 · « **Reply #4 on:** January 09, 2019,13:04:03 »

hi bruse thanks for the info, if the backlight as gone i should be able to see an image, which i don't, so a bit confused,

downunder · « **Reply #5 on:** January 10, 2019,00:52:49 »

Well no, Shaun. Once an error has been detected and the CPU generates an error code, Panasonic TVs are locked down thereafter. 1 second to black after switch on is usually a backlight fault in most LED TVs.

So, you have standby-5V present at all times. What about Power-On and BL-On voltages ? You may in fact have a faulty A-board (Main).

Mulja tv repair portal · « **Reply #5 on:** January 10, 2019,00:52:49 »

t1412 · « **Reply #6 on:** January 12, 2019,01:35:37 »

change the mainboard still the same i'll test the led thanks

Turnip · « **Reply #7 on:** January 12, 2019,10:44:37 »

Hi Shaun,

Leds don't always show as faulty. Had one with the 'one flash' where all four strings on the long side strip checked OK, even out of the set with 300 m/a up them (Strip got rather hot though, off the heatsink)

Answer was a new strip £40+ locally or £18 freepost from China if you don't mind the fortnight wait - Chris.

sinclairtv · « **Reply #8 on:** January 13, 2019,11:31:14 »

So has this set got sidelight or back lights.

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