Barco LCN-42 No Power

[Jasgriff]

Re: Barco LCN-42 No Power

I have found some PNP transistors with 100 Vceo but i'm struggling to find a 100ma one?

Farnell.co.uk

Would one of these do? Looking at your diagram I will need 1 NPN and 1 PNP.

[budm]

Re: Barco LCN-42 No Power

Most power supply works the same way, if you understand the basic, then when you trace out the connection on something you have not seen before, then it will make sense to you how it works, I hope I explain it well. When the SMPS goes high, it will turn on Q201 which will supply the VCC (12~15VDC? to the Gate of the MOSFET to turn it on), when it goes low, Q201 will turn off, Q202 will turn on and will discharge the internal Gate capacitor (insulation) inside the MOSFET to make sure it stops conducting ASAP (when it is told to turn off) due to charge remain on the Gate insulation, most circuit will use Diode for this function. This ON and OFF happens at very high speed, 50~100KHz, depends on circuits design.

[budm]

Re: Barco LCN-42 No Power

The NPN Q201 check OK right? What is the current rating? Higher rating is OK.

[Jasgriff]

Re: Barco LCN-42 No Power

The NPN Q201 check OK right? What is the current rating? Higher rating is OK.

Ahh i was worried that the rating was the draw? but its just the maximum that it can with stand.

Both Transistors are broken.

How about these 2?

http://www.diodes.com/zetex/_pdfs/3.0/pdf/FMMT593.pdf

http://www.farnell.com/datasheets/302332.pdf

[budm]

Re: Barco LCN-42 No Power

They will be fine, just make sure to not mix up the PNP, NPN when you install them.

[popeye]

Re: Barco LCN-42 No Power

Make sure you resolder all the DJ's I can see a lot of them.

[Jasgriff]

Re: Barco LCN-42 No Power

Make sure you resolder all the DJ's I can see a lot of them.

Disc Jockeys or bad solder joints?

[Jasgriff]

Re: Barco LCN-42 No Power

Quick update on where I am at with this one.

Ordered some 1 Watt 0.22 OHM metal film resistors and 3 Watt 0.22 OHM wire wound resistors. 1 to replace the blown and the others for spares.

Ordered a batch of T8AH fuses in case the board blows another.

Ordered the replacement Power Mosfet 11N80C3

Ordered some 33k SMD resistors to replace the 2 blown ones that connect to the transistors.

Ordered a bottle of Isopropyl Alcohol for getting rid of the flux and gunk.

Quick update....

The 3 Watt resistors came before the 1 Watt ones so I fitted one of those.

The power Mosfet has arrived and been fitted.

The Fuses have arrived

The Isopropyl Alcohol arrived and I gave the connections a good clean all around.

The transistors have been ordered today along with some caps to start replacing those too.

I'm going to go over those poor solder joints not to make sure that they dont cause any issue.

[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.

[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

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.

[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.

[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

[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

Well hopefully I will have a new one here on Friday

[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 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.

[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.

[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

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

Yeah 30k sorry.

Wont get the SMPS until Monday unfortunately.