dikom 22 lcd blown mosfet replacement

[dellxps15]

hi all today i got this tv with 1 sec backlight and no lcd image. after open it i found one blown mosfet Q11. after remove itr and check value i see it was lcd vcc, so did a jump after turning tv on and image (without backlight) comes in.

mosfet is mb9495e and cant find it anywhere. source was 5 volt, gate 5 volt and when i turn tv on gate goes to 0 , so it should be a n channel mosfet.

any suggestion on wich common mosfet i can use on that ? it will power lcd a 22 inch.

mainboard code is HD_D7102 rev 3.0 and its a common mainboard for low price tv-ready.

if i can fix that mosfet for low price, i can go and change ccfl for around 30€ and bring that dead tv back to life

[tvtimmy]

Re: dikom 22 lcd blown mosfet replacement

Check u19. It looks cracked.

[dellxps15]

Re: dikom 22 lcd blown mosfet replacement

tnx for reply. u19 is ok. was just some thin dust or similar

[SMDFlea]

Re: dikom 22 lcd blown mosfet replacement

Its an N channel mosfet, theres many differet parts with that part number 9435A ,i did find a datasheet though BM9435A

EDIT: see the attached Teac lcd221sd-service-manual. It has a different mainboard and the circuit may be different. Search for Q11 and 9435A

[budm]

Re: dikom 22 lcd blown mosfet replacement

5V on Source pin means it is P-CH, so for it to be on the Gate has to be about 3V < than Source pin, you have 0V when unit is turned on so that is correct.
That MOSFET is for supplying switched Voltage for the T-CON.
The link on post #4 is fine to use.

[SMDFlea]

Re: dikom 22 lcd blown mosfet replacement

Sorry budm,i did mean P-CH ,it was a typo .

[budm]

Re: dikom 22 lcd blown mosfet replacement

Sorry budm,i did mean P-CH ,it was a typo .

That's what I thought since you did find the correct MOSFET.

[dellxps15]

Re: dikom 22 lcd blown mosfet replacement

wow tnx very much for the reply. so if i get a FAIRCHILD 9435 would also be ok right ?

and if i use a normal p-channel that i have for notebook ?

like this one http://aosmd.com/pdfs/datasheet/ao4407.pdf


better stay safe and get that 9435 series ?

[budm]

Re: dikom 22 lcd blown mosfet replacement

The 4407 looks to have the same pinout and handle more current and lower Rds, but the typ. Vgs is higher (-2.25V VS -1.5V).
You can try it out but you need to check the Voltage between Gate and Source to make sure it is at least 2.25V or more to make sure it is fully on.

[dellxps15]

Re: dikom 22 lcd blown mosfet replacement

when board is off i have 5 volt on gate and source. when power on the board i have 5 volt source and 0 volt gate.

[budm]

Re: dikom 22 lcd blown mosfet replacement

when board is off i have 5 volt on gate and source. when power on the board i have 5 volt source and 0 volt gate.

Just to be sure, you need to measure between Gate and Source pin, not Ground.

[dellxps15]

Re: dikom 22 lcd blown mosfet replacement

hi all, today after first ship didnt arrived, i ordered a second time that mosfet and tv was giving image back, but i noticed some weird issue :

if tv start with backlight, i have no sound, and if i disconnect the backlight 12 volt connector that goes to the transfoermers, i have audio working fine, but as soon as i plug the backlight cable and got perfect image on lcd, audio dont work annymore.

what could be the cause ?

also that tv has an integrated dvd rom. if i playback a movie, i have no audio and after 5-10 mins the image start goin on and off and voltage measuring goes crazy, i didnt try the dvd video playback with the backlight cable disconnected to see if i have audio.

sometimes both audio and backlight were working, but audio was not 100% working, it randomly goes on and off.

[dellxps15]

Re: dikom 22 lcd blown mosfet replacement

i made some measurement and when i have audio, on red dot i have 11.5 volt, while when there is no audio, i have 5.12 volt.

sometimes i have 11.5-11.8 volt on that red dot with working backlight and audio too is working fine.

[dick_barton]

Re: dikom 22 lcd blown mosfet replacement

That's the mute input pin to the audio amp. Check the headphone socket is in good condition.

Check connector J9 that the mute switch pin 7 is secure

[dellxps15]

Re: dikom 22 lcd blown mosfet replacement

ok i see that m/ss on similar schematic posted on N#4 . i tryied plug in headphone and as i plug them i ear sound on headphone, but inssert and remove headphone didnt give back sound to speakers.

also if i turn off tv, if tv start without backlight i ear sound, but if tv start with backlight, i have no sound

[dellxps15]

Re: dikom 22 lcd blown mosfet replacement

i dont have that j9. it must be a separate j pinout as i have 3 pin for ch+ ch- source menu vol+ vol- and power on/off.

also audio without touching anything sometimes work after a while sometimes goes off, on again.

other big problem is dvd play. as write on previous post, if i play a dvd rom, i have image but no audio and after 5-10 min video goes on and off and volts reading goes crazy.


im suspecting a big chip failure at this point.

ive found a similar board with different brand for 20€, but dunno if it will work fine, will last fine and even more dunno if that tv is worth the repair ( its not even hd ready.. selecting a dtv hd channel it say not supported)

[dellxps15]

Re: dikom 22 lcd blown mosfet replacement

update: after some time tring to figure out wat was wrong, i ear a noise from psu when backlight and audio were both working. i measured psu volts (its external 12v 5A) and measured 12volt when tv is powered off. when i power on tv volts goes down to 6 volt then back to 10-11.5 volt max and psu was getting really hot.


i tried with bench psu and each time i got stable 12 volt ofcourse and Ampere were going from 0.11 in standby to 4.5 when tv was powering on and go to a stable 4.04A when tv was on with both backlight and audio working on each power on off try i did.
today i opened the psu and found the 120uf 400volt capacitor blown, another 1000uf 16v blown. ill replace all caps in here and post results tomorrow.

[dellxps15]

Re: dikom 22 lcd blown mosfet replacement

update of today: i replaced the caps on psu and now tv is working fine and in all function

tnx for the help

[dick_barton]

Re: dikom 22 lcd blown mosfet replacement

Thanks for the follow up.

[nomoresonys]

Re: dikom 22 lcd blown mosfet replacement

Nice work, many times an audio problem as you described is a good indication of a bad cap/s. I would have suggested it but I guess I assumed that you already looked them over.