Benq FP91E no power

[sternelch]

Hello,
i have a Benq FP91E.
Some months ago it had 2 seconds to black so i opened it and saw some elkos looking dead so i changed it and the screen was working again.
Some time after that it again had 2 seconds to black so I changed all elkos (except the one on the left top corner, because I think they are only for sound?) and resoldered the transformers and C5707 (on top of the picture).

It works some months but now the screen is black (not even 2 seconds) and also the power led isn´t working.
I measured the C5707 and think they are ok...
pin 2->3: 560Ohm
pin 3->2: ~120kOhm
pin 1->2,1->3: ~18MOhm

Mainfuse and Picofuse are also working (0.3 Ohm)

The board is still "cheeping" like it was before when i opened it with power plugged in.

As you can see the a trace "burned" as i tried to run it disassembled, hopefully nothing bad happened, the trace has still a connection.

Greetings from Austria.

[lexwalker]

Re: Benq FP91E no power

i have a Benq FP91E.
Some months ago it had 2 seconds to black so i opened it and saw some elkos looking dead so i changed it and the screen was working again.
Some time after that it again had 2 seconds to black so I changed all elkos (except the one on the left top corner, because I think they are only for sound?) and resoldered the transformers and C5707 (on top of the picture).

It works some months but now the screen is black (not even 2 seconds) and also the power led isn´t working.

When it first occured, should have gave it a major re-capping especially all those capacitors on the inverter side. Usually for 2 seconds to black, you should check the inverter transformers.

I measured the C5707 and think they are ok...
pin 2->3: 560Ohm
pin 3->2: ~120kOhm
pin 1->2,1->3: ~18MOhm

Do you really know how to test a NPN transistor? Use the continuity test on the multimeter. Ensure that you use the correct polarity (red for +ve and black for -ve). There should be low resistance reading between pin 1->2 (base to collector) and 1->3 (base to emitter). Then there should be very high resistance or open reading between 2->1 and 3->1 in opposite polarity. Also pin 2->3 and 3->2 (both polarity) should be high resistance or open. Make sure you identify pin 1 (base) properly. Datasheet here: https://cdn.badcaps-static.com/pdfs/...37131164fb.pdf

Mainfuse and Picofuse are also working (0.3 Ohm)

The board is still "cheeping" like it was before when i opened it with power plugged in.

As you can see the a trace "burned" as i tried to run it disassembled, hopefully nothing bad happened, the trace has still a connection.

If the board has "cheeping" sound, its quite likely coming from the transformers. From the looks of the tops of those capacitors, seems like Teapo...