Benq FP91G+ Monitor

[matthmal]

Re: Benq FP91G+ Monitor

check thes mosfet in the inverter FU9024N e c5707 ! and 'success that face to the white screen to monitor. controls the condensers 0.22 between the C5707.

which one's should I check?

[killian6pk]

Re: Benq FP91G+ Monitor

which one's should I check?

What he was trying to say is that BenQ boards have not only the 5707's but they also have another part that looks exactly the same. On the picture of your powerboard on top you can see a part location number of Q805 and next to C821 there is another one of those. I think he gave you the correct part number for them if I recall correctly. You should pull each of them and check them also as they go bad usually right along with the 5707's. Check the part numbers and list them and Bud can tell you how to test them. I have repaired several BenQ boards and each of them have had that part be toasted right along with the 5705's.

[matthmal]

Re: Benq FP91G+ Monitor

The model numbers are as follows:
Q805:
D10PF
06
GK05W546

Q812:
D10PF
06
GK1C1545

[budm]

Re: Benq FP91G+ Monitor

Spec sheet. If this MOSFET has shorted out S to D, the backlights will be fully on bright and not be able to adjust the lamp brightness. It is driven by the PWM signal to vary the B+ feeding the backlights ROYER Oscillator output circuits.

[lexwalker]

Re: Benq FP91G+ Monitor

After re-soldering the C5707 transistors, I now have a new symptom. The monitor works for a while and then turns off. I switch it on again and works for a couple of minutes or hours and shuts down again.

I tested the 3 pin voltage regulator and got the below results:
Pin 1 -> 3.3V
Pin 2 -> 1.8V
Pin 3 -> 0.00V

I still need to test the regulator when the monitor fails though as I tested it while it was on and working.

Came across this monitor quite a few times before, and I suggest you check the primary side as well. Quite a number of them had rather "dry" main filter/smoothing capacitors (that 100uF 450V thingy). One I've fixed had major primary side failure with the main MOSFET, current sense resistor, etc all blown as well (including a dry main filter/smoothing capacitor also). Thus I would suggest replacing all those capacitors on the primary side also. Check and/or replace the current sense resistor and MOSFET (either a 2SK3264 or STP7NK80ZFP) also...

[Davi.p]

Re: Benq FP91G+ Monitor

matthmal i'm sorry, i've seen now that i don't have read with full attention your post, i read that you've changed only 2 5707, in that monitors there are always 4 and must be replaced all 4 'cause ususally 1 or 2 goes evidently short, the other 1 / 2 goes short under normal activity, maybe yours goes short after some minutes, i don't think you have to change things on primary side like lexwalker says 'cause you first can try the previous and at least try voltages on secondary.

TO Retiredcaps:
i'm unable to translate "You are going to give someone" but the message is almost clear, i think is not an huge job to put a "?" at the end of a phrase, it makes more clarity to an already difficult (for me , maybe for you is all "freshwater") theme . I don't like the smilies icon you put, i don't think i have to receive a smash from you!