Samsung 940NW - 2 seconds to black - now just black!

[kktlam]

Re: Samsung 940NW - 2 seconds to black - now just black!

Hi RetiredCaps,

I measured F301 again just to be sure: it was continuous (0.05 ohm, using 200 ohm range.)

DC voltages at CN2, whether the logic board was connected, read:
15 V terminal: 13.49 V
5 V terminal: 5.13 V

Kevin

[retiredcaps]

Re: Samsung 940NW - 2 seconds to black - now just black!

Did you check fuse F301?

[retiredcaps]

Re: Samsung 940NW - 2 seconds to black - now just black!

What are the DC voltages at CN2 (connector)?

[kktlam]

Dear experts,

I have been to many other hobbist/expert forums but only this one exhibits such helpfulness and wealth of knowledge! (Troubleshooting electronics remotely is a hard thing to do!) This is such a great forum and I congratulate and thank everybody who has contributed.

So here is another newbie's (typical) story:
My friend wanted me to help fix a monitor as titled, exhibiting the "2 seconds to black" symptom, with the video still visible under flashlight. I opened it up, replaced all the caps with new low-ESR ones, but it became worse: now the backlight doesn't even come on, and the video signal is gone! Only the blue power LED stays on for 2s and then flashes slowly at about 1 flash per second.

Now having "gotten my hands dirty" I want to get this monitor fixed, and so hoping you folks can give me some ideas! I have already done the following (according to the sticky thread):

- Replaced all the radial electrolytic caps except the main filter (big) capacitor
- Checked the resistance of all the MOSFETs (no shorts), fuses (no opens), and transformer secondaries (identical resistance); I "assume" all are OK.

Suggestions are welcome!! Attached are PSU board photos.

In advance, a big THANKS!

Kevin