Barco LCN-42 No Power

[Jasgriff]

Re: Barco LCN-42 No Power

It definitely looks more silver than grey its got a shine to it.

Q203 is also shorted. One of the legs of that connects to the resistor so that could have been what caused it?

[budm]

Re: Barco LCN-42 No Power

I Know, I will look through my spare boards and see if they have one of these five band power resistor and see what the value should be. Does it look Gray or Silver to you? If it is gray, then that will be real odd ball value.

[Jasgriff]

Re: Barco LCN-42 No Power

If it is the Source resistor, I would think so since most of the power supply I worked on has Source resistor from 0.1~0.47 Ohm range. That 3rd band with silver color (it looks silver to me from the pictures)

According to the calculator it cant be silver on a 5 band resistor?

http://www.maplin.co.uk/search?criteria=resistor

Here is where I will be going tomorrow to get a couple of fuses. There is no sign of a resistor that looks like its going to do the job. Its a poor version of radio shack.

[budm]

Re: Barco LCN-42 No Power

If it is the Source resistor, I would think so since most of the power supply I worked on has Source resistor from 0.1~0.47 Ohm range. That 3rd band with silver color (it looks silver to me from the pictures)

[Jasgriff]

Re: Barco LCN-42 No Power

Yes, I figured that out in post #19, but I guess you didn't see the post before post #20?

4th band looks brown.

Long time since I was in college learning the bands off by heart lol.

[Jasgriff]

Re: Barco LCN-42 No Power

That looks like the Source resistor for the MOSFET next to it, more likely to have Source to Drain shorted out, since the voltage drop on this resistor will be use for the Overcurrent feedback for the SMPS IC, if the value is too high then it will cause the power supply to shutdown too earlier, if it is too low, then it will not go into shutdown when the current is already exceed the current limit of the MOSFET and other power component. I would think it will be about 0.20 Ohm MOX type 1W (you can calculate the Wattage if you know how much current is expected to flow through this resistor). By the way, I can see a lot of failings solder joints.

Yes I noticed that they looked bad when I reviewed the pictures. I will go over the whole board and give them a touch up.

Do you think that resistor is that low considering the bands that can be seen?

[retiredcaps]

Re: Barco LCN-42 No Power

The middle band cant be silver according to this website.

Yes, I figured that out in post #19, but I guess you didn't see the post before post #20?

4th band looks brown.

[budm]

Re: Barco LCN-42 No Power

That looks like the Source resistor for the MOSFET next to it, more likely to have Source to Drain shorted out, since the voltage drop on this resistor will be use for the Overcurrent feedback for the SMPS IC, if the value is too high then it will cause the power supply to shutdown too earlier, if it is too low, then it will not go into shutdown when the current is already exceed the current limit of the MOSFET and other power component. I would think it will be about 0.20 Ohm MOX type 1W (you can calculate the Wattage if you know how much current is expected to flow through this resistor). By the way, I can see a lot of failings solder joints.

[Jasgriff]

Re: Barco LCN-42 No Power

The middle band cant be silver according to this website.

http://www.diyalarmforum.com/5-band-resistor-calc/

I have attached a better pic.

[retiredcaps]

Re: Barco LCN-42 No Power

Does Red Black Silver Brown Green look about right for that resistor?

With the above, according to the URL below, it is invalid.

http://www.hobby-hour.com/electronic...calculator.php

The silver might be gray? It is the 3rd and 4th band I'm unsure of. Initially I thought the 3rd band was silver and it still looks more silver than gray to me. However, I see the 3rd band can ONLY be gray due to it being a 5 band resistor.

That would make it 2.08k ohm 0.5% resistor if the 4th band is brown.

Maybe post another pic showing it rotated 180 degrees and try cleaning the resistor up with some isopropyl alcohol?

[Jasgriff]

Re: Barco LCN-42 No Power

Does Red Black Silver Brown Green look about right for that resistor?

[Jasgriff]

Re: Barco LCN-42 No Power

See if it reads close to 0.0 Ohms. If yes, then it is okay.

edit: It is odd that J33 shows 000 and J34 shows just 0.

It shows 000 as I store that off another board and replaced the blown one.

It reads close to 0 OHMS and I have traced it back to the nearest components each side and it still shows as close to 0 OHMS.

See I did such a good job you couldn't tell it was re soldered lol

[retiredcaps]

Re: Barco LCN-42 No Power

I will Check the Rectifier and Mosfet now.

Maybe hookup a light bulb in series after replacing all the components since the fuse is blown?

http://www.repairfaq.org/samnew/tvfaq/tvtslbt.htm

[retiredcaps]

Re: Barco LCN-42 No Power

Does the Jumper repair look good enough?

See if it reads close to 0.0 Ohms. If yes, then it is okay.

edit: It is odd that J33 shows 000 and J34 shows just 0.

[retiredcaps]

Re: Barco LCN-42 No Power

if do you you possibly have access to the service guide for it?

How good are you at guessing file names?

I found

http://www.fspgroupusa.com/fsp4173m01/p/769.html





but neither show a schematic of the power supply.

[Jasgriff]

Re: Barco LCN-42 No Power

Whenever I see a blown fuse, I always check the bridge rectifier and power mosfet to see if they are shorted.

I will Check the Rectifier and Mosfet now.

Here is a proper picture of the blown resistor it is showing as 'OL' so its definitely gone.

[Jasgriff]

Re: Barco LCN-42 No Power

I am sure that if I can see 2 failed caps then the others will more than likely be in poor condition.

I have fixed the SMD Jumper so now I am thinking replace the Fuse the Resistor and patch the broken track then give it a try?

Could that resistor blowing be responsible for the board damage?

Does the Jumper repair look good enough?

[retiredcaps]

Re: Barco LCN-42 No Power

Blown Fuse!

Whenever I see a blown fuse, I always check the bridge rectifier and power mosfet to see if they are shorted.

[retiredcaps]

Re: Barco LCN-42 No Power

Safe to say its well and truely gone though? Do you know what wattage it might be it looks massive.

Try and measure the resistor out of circuit first to see if the first digit is a "2" for the "red band" on your Fluke 175. It might even show up as 19??? or some close variation.

I'm not the greatest at spatial awareness so I'll pass on the guessing. However, it looks like you have a lot of room around it so if you guess really high for wattage, then it will fit and you have a safety margin.

[retiredcaps]

Re: Barco LCN-42 No Power

Looks like a couple of caps have had it.

In the motherboard and ATX PS sections of this forum, a lot of people say that OST branded caps can fail without bloating. I see some OST caps on your board.