Samsung 2493HM/BN4400195A: let's cut it finally!

[Behemot]

All those other threads got so messy I decided to start a new one and try to go through all possibilities to bring it back to the alive ones. I still got that first one, unable to repair it with possibly bad main transformer or resonant transformer So if not both, at least making one out of two would be possible solution.

So I got second one, with that yellow bloat carbonated almost at each spot, both transistors, 0R22 resistor and one fuse blown. At least it was easy to get rid of that glue. Cleaned it everywhere, I've replaced transistors, resistor and fuse.

When I plug it in just as it is, I get +5 V SB OK. With inverter connected and running on light bulb, I get no image but the bulb blinking and some noises like if something was in short from inside the display.

I found no bad semiconductors - at least not shorted, still there is possibility of some of those bloody zeners not working. I do have 2kV O-scope probe this time so I can proceed with measuring the main transformer primary, but is there anything else to check first? I also do have Karl-Heinz Kübbeler's universal tester as CT-Micro v1.0 from Mikhail so I can do more proper testing of components this time!

• replaced main transistors
• replaced RM801 0R22
• replaced fuse
• cleaned all that stuff
• checked semiconductors with diode tester
• checked CM812 fine (15,6 nF)
• checked RB801S (44R) - measures 33 ohms in curcuit
• checked RB808 (2R) OK
• checked RB802 and the other one (100k), OK
• checked caps, they are good to replace but nothing drastically out of spec on first sight
• main stransformer primary measures 74 mH
• measured CM809 65 pF

[selldoor]

Re: Samsung 2493HM/BN4400195A: let's cut it finally!

If there is an arcing/ shorting noise from the display then make up another test bulb
and try and eliminate the noise. Have you tried the test bulb you have in place of each bulb?
Now wondering if you have a test bulb in place of one ccfl or you mean your using the dim bulb test on the mains input.

[Behemot]

Re: Samsung 2493HM/BN4400195A: let's cut it finally!

I have the bulb in series with the power supply board, to protect it from burning if there is any problem on the hot side.

[selldoor]

Re: Samsung 2493HM/BN4400195A: let's cut it finally!

Yes that what I wondered.
How about plugging the bulbs from set one into the inverter to see if they light and noise stops?

[Behemot]

Re: Samsung 2493HM/BN4400195A: let's cut it finally!

What is set one? All six lamps were connected to inverter.

[Behemot]

Re: Samsung 2493HM/BN4400195A: let's cut it finally!

CM809 measures 100 pF out of circuit, should be 47, will replace and try.

[selldoor]

Re: Samsung 2493HM/BN4400195A: let's cut it finally!

What is set one? All six lamps were connected to inverter.

You said
I still got that first one, unable to repair it with possibly bad main transformer or resonant transformer So if not both, at least making one out of two would be possible solution.

So I was suggesting plug its back lights , or one of them into this second set/monitor/ machine

[Behemot]

Re: Samsung 2493HM/BN4400195A: let's cut it finally!

I see. Well that PSU was not working either so I don't really see how that could help. Both had blown transistors and that 0R22 resistor, don't think there is anny difference in the selection, just maybe the second was easier to clean of the glue so it may be done better.