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Nokia Mono Plus II - Dead with Stand-by LED flashing

 
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arabidopsis



Joined: 02 Jul 2011
Posts: 1
Location: Portugal

PostPosted: Sat Jul 02, 2011 7:27 pm    Post subject: Nokia Mono Plus II - Dead with Stand-by LED flashing Reply with quote

Hello!

I have a TV Nokia, chassis Mono Plus II for repair (first time I met this chassis).
It does not power up but makes a short hiss (apparently tries to start and shuts down immediately) and Stand-by LED remains flashing.

Voltage in the switching supply capacitor was only 175V and after replacing input rectifier diodes (all measured OK but one dropped 85V!), was corrected to the required 325V.
Except for the TEA2164, all significant components in the switching supply were measured or replaced.

However the voltage supply to pin 16 of TEA2164 remains at 3.4V (should be 10-14.5V) and voltage at pin 3 is 4V, when it should be <1V (overload protection?).
Any suggestion about what can be causing this?

If it's anywhere in the switching supply, it does not make much sense, as the microprocessor is driving the LED and, for that, needs power that is provided by the TEA2164 + BUF405.
Anyway, replacing the TEA2164 for testing or repair is not an option (at 40€ unit cost, better trash the TV).

I can't find repair tips for this fault anywhere and most replies I found in web forums are simply useless.

I just hope someone here knows this chassis and can shed some light on the origin of this fault.

Thanks in advance for any help.

Jose
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torbjorn



Joined: 07 Jun 2007
Posts: 370
Location: Sweden

PostPosted: Fri Jul 08, 2011 11:51 am    Post subject: Reply with quote

I have encountered the same symptom due to a faulty flyback transformer in a Nokia Euromono chassis. Try the classic troubleshooting method of disconnecting supply to the horizontal output, load the power supply with a 230 V 40 W bulb and check if the power supply then delivers correct voltages. Of course, it could be any other problem with the horizontal output too, not necessarily the transformer.
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