MX4000 TV shuts off after a few seconds (Last error power fail)

Hello, I have a Bang & Olufsen MX4000 television. The TV turns on perfectly but after a few seconds the TV switches off. When I enter service mode, this message appears: "last error pf"(power fail). I have changed the capacitors C29, C31, C32, C44, C46, C48, C52, C53, C61, C82, C100,C120, C121, C131, C132, C134 and C137 but the problem persists. I hope you can help me. Thank you very much.

Nobody can help me?

Take a look here.

https://archivedarchivedforum2.beoworld.org/forums/p/11692/87246.aspx#87246

This is a post from the archived forum. You can do asearch there on your own.

Powerfail is the self protection system built into the design,it monitors the various sections of the tv for excess consumption,and shuts the set down to avoid damage.The operation is explained in the tv service manual,and also some advice on faultfinding.

In my experience,the most common cause of shutdown is faults in the deflection and high voltage sections.A useful test is switching the tv on in it's audio only mode ie audio-aux via the remote,or shift radio.If the tv comes on(no picture) and stay's on,this will confirm this.

"usual suspects"in the deflection stage are C102 dry jointed,the transistor itself TR33 and diodes D80/81,but other soldered joints may be suspect now of course.The actual pins of the line output transformer can push through the pcb over the years.

Great little telly's,worth tinkering with,but take care,some high voltages abound even when the set is off.

Nick

I replaced the transistor TR33 and C102 with another one. I have taken advantage of these two pieces of the PCB of a TV MX6000. I have measured diodes D80 and D81 and the result is 518 and 514 respectively. I have also checked welds. I do not know what to do ...

EDIT:I turned on the TV and pressed "V.TAPE" but the TV goes off.

The failure could be anywhere in the set,but is most likely to be in the high voltage/deflection stages.

V.Tape of course is a function that would use this stage,so if the problem is there,the set will still shut down!

You need to try the set in it's audio mode by pressing "audio-Aux" or "shift -radio".What happens if you do this?

Nick