Barco LCN-42 No Power

[Jasgriff]

Re: Barco LCN-42 No Power

Ok checked the VCC of the SMPS IC and it is showing 13.4v. This seems to be right. I will check the Mosfet now.

Ok 390v On the mosfet I have included a pic of the whole bottom of the board and how I measured it.

[Jasgriff]

Re: Barco LCN-42 No Power

You cannot see the gas discharge components as they are just hidden in this picture.

See the big grey component on C1 I think this is where the noise is coming from.

I will take a proper picture of where the flashes are coming from and I will check that the SMPS ic has power and the Mosfet that I changed.

Apparently I have to watch a film now so I will try and do that once its finished.

[budm]

Re: Barco LCN-42 No Power

I think they are Gas Discharge tubes for surge protection (I do not see then on the top view of the power supply board picture), they should not flash (Conduct)unless there are surges, they should be rated at about 400v or more.
Can I see the pictures?
Well, the circuits are still not working. We replaced the damaged parts for the 18VDC power supply. We need to see if we have Vcc the SMPS IC you just installed, also recheck your soldering works just incase, right now the middle pin (Drain) of the new MOSFEt should have DC voltage on it, can you verify that?

[Jasgriff]

Re: Barco LCN-42 No Power

Noticed something else...

GT1 + GT2 which are near the main fuse flash when I turn the power on. They look like Zener Diodes im guessing they are not supposed to flash?

[Jasgriff]

Re: Barco LCN-42 No Power

Right Parts fitted!

I first turned it on for a short period of time and could hear a slight noise.

Not sure if it was anything to worry about I turned it off and then tested the fuse etc to see if it had tripped again and it hadnt.

I powered it back up and the 24v rail seems fine but the 18v one has no power. I also tried the 5v rail and this was just over 5v and steady.

Does this mean the new smps ic and the transistors have worked because I now have power to those rails or was that smps looking after the 18v rail and thats why its not working?

[Jasgriff]

Re: Barco LCN-42 No Power

Right got the bits before I fit the transistors.....

Q201 = npn
Q202 = pnp

I recall it being the other way around so I thought I would check

[budm]

Re: Barco LCN-42 No Power

The suspense is killing me!

[Jasgriff]

Re: Barco LCN-42 No Power

SMPS have arrived. Hopefully I will have them in my possession tomorrow night. Then we can see whats going on

Also just won 2 more monitors to play about with which I should have in a couple of days.

[Jasgriff]

Re: Barco LCN-42 No Power

Can't wait!
Is it 3k or 30k?
30k in post #57

Yeah 30k sorry.

Wont get the SMPS until Monday unfortunately.

[budm]

Re: Barco LCN-42 No Power

Can't wait!
Is it 3k or 30k?
30k in post #57

[Jasgriff]

Re: Barco LCN-42 No Power

3K SMD's have turned up today and they have been fitted.

So just waiting for the SMPS and the transistors then we are ready to go.

[Jasgriff]

Re: Barco LCN-42 No Power

Well I have ordered 4 mosfets 3 chips 10 resistors and seven fuses so I have a few spares to try out.

I can imagine its difficult working things out when its not in front of you.

Here is another one of the board that I took to show you which parts provide which voltages.

[budm]

Re: Barco LCN-42 No Power

Crossing my fingers that I got the digram correct per what I could see from the pictures, long distant troubleshooting is not easy, that is why real good pictures come in to play.

[Jasgriff]

Re: Barco LCN-42 No Power

Well hopefully I will have a new one here on Friday

[budm]

Re: Barco LCN-42 No Power

Yes I would have replaced it than taking a chance of blowing up new parts and caused more damages.

[Jasgriff]

Re: Barco LCN-42 No Power

So you would both change the IC rather than giving it a try?

I knew what your answers would have been so I have removed that IC also.

I did lift the pad on pin 7 this pin is not used luckily! It also looks like Pin 8 HV is not connected to anything, not sure if its an optional thing?

http://www.datasheetcatalog.org/data...swapill4cy.pdf

Ok had to order them from the US so I guess I will have to wait a few extra days to see if it fires up

[tom66]

Re: Barco LCN-42 No Power

It will also blow the fuse and could damage the PFC diode and bridge rectifier in rare circumstances.

[budm]

Re: Barco LCN-42 No Power

If the SMPS IC is not putting the pulses to switch the MOSFET on and off but stuck with steady High output, the MOSFET will be fully on, and that can damage the MOSFET and the transformer.

[Jasgriff]

Re: Barco LCN-42 No Power

I still have a feeling that the SMPS IC may be damaged also due the fact that the resistors and the transistors are damaged also.

Will it cause any more damage if I try?

[budm]

Re: Barco LCN-42 No Power

I still have a feeling that the SMPS IC may be damaged also due the fact that the resistors and the transistors are damaged also.