Sync Master 940n fuse

[rtstorm]

Hi, monitor did not light up backlight. I replace caps on it and i have 1-2 sec backlight and then secondary fuse blown. can you help me

[philliesfan30m]

Re: Sync Master 940n fuse

that mosfet on the heatsink might be bad. get the number off the mosfet. you might have other problems as well.

[rtstorm]

Re: Sync Master 940n fuse

it is MBFR20100CT i check it with diode test and OK

[philliesfan30m]

Re: Sync Master 940n fuse

test the mosfets on the other heatsink

[selldoor]

Re: Sync Master 940n fuse

Check you put the caps in the right way round?

[rtstorm]

Re: Sync Master 940n fuse

other one is DMO565R it has a 6 leg. CAnnot find datasheet

[rtstorm]

Re: Sync Master 940n fuse

caps is in the right way

[rtstorm]

Re: Sync Master 940n fuse

is this readig ok on CCFL transformer i have shorted all primary

[lexwalker]

Re: Sync Master 940n fuse

other one is DMO565R it has a 6 leg. CAnnot find datasheet

Not that one (which sounds like FSDM0565RB switched mode PWM power I.C)...

is this readig ok on CCFL transformer i have shorted all primary

Check the attached image. Remove the MOSFETs (as highlighted in yellow) and measure them off the board. These are surface mount MOSFETs. Also a reading of 1.3kOhm is little high for the transformer secondary windings (usually around 1.1kOhm or less). Possible bad transformer...

[Davi.p]

Re: Sync Master 940n fuse

very nice added graphics in your post #8 image.. which program do you use?
Also follow Budm posts, he links always a method to test for bad ccfl using unusable broken low-consumption cfl lamps.

[rtstorm]

Re: Sync Master 940n fuse

@ Davi.p - program is 'Jing' and its a free screen capture tool, i use it all the time

You ment sticky thread?

[rtstorm]

Re: Sync Master 940n fuse

that 2 MOSFETs is a 4502C how can i test them? In datasheet i can understand where is the D,G,S

[rtstorm]

Re: Sync Master 940n fuse

i check them, and i this i found a fail

one og them is shorten on pin2 and pin 7, other is 71kOHM and thay are the same markings (4502C AA6PN)

[Davi.p]

Re: Sync Master 940n fuse

ok let us to know if you fix it when you will change it.

[rtstorm]

Re: Sync Master 940n fuse

ok, i will order it and feedback when arives

[lexwalker]

Re: Sync Master 940n fuse

that 2 MOSFETs is a 4502C how can i test them? In datasheet i can understand where is the D,G,S

According to the service manual, supposed to be AM4512C but it seems the manufacturer were using AM4502C on your unit...

i check them, and i this i found a fail

one og them is shorten on pin2 and pin 7, other is 71kOHM and thay are the same markings (4502C AA6PN)

Yups, that would have possibly cause the fuse to blow. You may want to replace both of them (with new ones) just in case. As for the 2 seconds to black, check the secondaries of the second transformer and see if they are the same as the first transformer. As mentioned earlier, 1.3kOhm sounds a little high...

[rtstorm]

Re: Sync Master 940n fuse

i replace 2 MOSFET and monitor is now working, thank you all.