47LV5400 Component Values and Schematics

[Elwood]

I'm not ready to troubleshoot this board yet because there is a visible component failure. L502 blew! Can anyone tell me the value of this inductor? I tried reaching out to the folks who sell the repair kits for this board and they said that component is not a common failure item.

[diif]

Re: 47LV5400 Component Values and Schematics

I don't think it's value is too critical, but I'd suspect something else maybe shorted, like the mosfet(s) below it.

[yokoono]

Re: 47LV5400 Component Values and Schematics

Correct. I don't think that coil is faulty either. Only if it is interrupted. The defect is elsewhere.

[Elwood]

Re: 47LV5400 Component Values and Schematics

ummm look closely at the image. The choke is not there. It disintegrated! If you have a schematic and/or could tell me the value of the choke it would be helpful. If you have the part/no for the mosfet maybe I can check that it is not shorted.

[will62]

Re: 47LV5400 Component Values and Schematics

Looks like the 42LV770s uses the same components for the 0.9v power. I think that L502 is a BLM18PG121SN1D. As others said, that's probably not your only problem.

Edit: added a SM that may help

[budm]

Re: 47LV5400 Component Values and Schematics

Start by checking the resistance of C503 or 505 or 513.
Same for the MOSFET's as suggested.

[Elwood]

Re: 47LV5400 Component Values and Schematics

Thanks for the info Will62! I saw your reply this afternoon and couldn't wait to get home to give it a go. I tore into it and removed the caps. Still shorted! Damn. I immediately felt sad. Next, I cut the trace leading to IC501. Still Shorted. Removed, Q503 and of course no more short. I will try Digikey and Mouser unless anyone has a better suggestion. I'll order a couple of each just in case. Any other suggestions appreciated.

[budm]

Re: 47LV5400 Component Values and Schematics

Shorts between what?
So the high side MOSFET Q503 is shorted between S and D, but was there shorts between GROUND and the output side of the L502?
MOSFET Q503 is on the high side, if it shorted out it will not cause you to see short circuit between GROUND and the output side of L502.
Check the resistance between Ground and L505 to see what you get.

[R_J]

Re: 47LV5400 Component Values and Schematics

If removing Q503, removed the short from L502, and Q503 was shorted, you will likely also have Q508 shorted as it's Source connects to ground, Also check R577 & R578, if either one is open, IC501 may be damaged. I would also check from L505 to ground to make sure there is no short on that +0.9V_core line.

[Elwood]

Re: 47LV5400 Component Values and Schematics

If removing Q503, removed the short from L502, and Q503 was shorted, you will likely also have Q508 shorted as it's Source connects to ground, Also check R577 & R578, if either one is open, IC501 may be damaged. I would also check from L505 to ground to make sure there is no short on that +0.9V_core line.

Q503 was shorted from gate to ground. The resistors are OK. Q508 appears to be OK but I would change it if I can get one.

No luck finding the Mosfet in the USA or Canada but lots in China and elsewhere. In my industry the Chinese semiconductors were bad news but I don't think this will be the case on a 25-cent item. Anyhow, I was hoping to wrap this up. I messaged a USA ebay seller who sells parts for this board as they also do repairs. He replied quickly and said he only stocks the common failure parts. In my research I found a spec sheet that said the device was commonly used in laptop motherboards so I will try a laptop repair center on Monday. Any other sources I should try?

[R_J]

Re: 47LV5400 Component Values and Schematics

Q503 was shorted from gate to ground. The resistors are OK. Q508 appears to be OK but I would change it if I can get one.

No luck finding the Mosfet in the USA or Canada but lots in China and elsewhere. In my industry the Chinese semiconductors were bad news but I don't think this will be the case on a 25-cent item. Anyhow, I was hoping to wrap this up. I messaged a USA ebay seller who sells parts for this board as they also do repairs. He replied quickly and said he only stocks the common failure parts. In my research I found a spec sheet that said the device was commonly used in laptop motherboards so I will try a laptop repair center on Monday. Any other sources I should try?

Looking at the schematic, How could you have a short from gate to ground within Q503? Q503 drain or source does not connect to ground.

[Elwood]

Re: 47LV5400 Component Values and Schematics

Sorry, I should have said gate to source. The source connects to the 0.9V Core which is very high current and reading from it to ground is as good as ground to my meter. The 0.9V output is very high current so I'm not expecting to see any difference between this line and ground. If this is not the case, please let me know.

[R_J]

Re: 47LV5400 Component Values and Schematics

ok, so Q503 must have ALL pins shorted, gate to source and drain.

[Elwood]

Re: 47LV5400 Component Values and Schematics

My bad. Shorted source to drain. If the gate was shorted the 4.7 ohm resistor would have probably blown and it didn't.

[budm]

Re: 47LV5400 Component Values and Schematics

Sorry, I should have said gate to source. The source connects to the 0.9V Core which is very high current and reading from it to ground is as good as ground to my meter. The 0.9V output is very high current so I'm not expecting to see any difference between this line and ground. If this is not the case, please let me know.

"reading from it to ground is as good as ground to my meter" What does that mean 'as good as ground"? What is the resistance reading between Ground and Source (or L505)? High current has nothing to do with it.

[Elwood]

Re: 47LV5400 Component Values and Schematics

I wasn't sure what you were getting at because the output voltage is 0.9V and the current is max 7350 mA so the resistance should be around 0.12ohms. Even if the current was half of that, the load would still be barely readable with my crappy meter. That got me to thinking that I should check the power supply output caps as one might be shorted. I removed C522 and C525 and the line is still looks shorted to ground. Does anyone know if the core current is always near the 7350mA rating or only when running full out? Does anyone have a schematic of the rest of the board? Is it time to assume the 35230 is bad and find myself a used board?

[budm]

Re: 47LV5400 Component Values and Schematics

I wasn't sure what you were getting at because the output voltage is 0.9V and the current is max 7350 mA so the resistance should be around 0.12ohms. Even if the current was half of that, the load would still be barely readable with my crappy meter. That got me to thinking that I should check the power supply output caps as one might be shorted. I removed C522 and C525 and the line is still looks shorted to ground. Does anyone know if the core current is always near the 7350mA rating or only when running full out? Does anyone have a schematic of the rest of the board? Is it time to assume the 35230 is bad and find myself a used board?

That is not how it works in this case, it does not mean you will see 0.12 Ohms at the output because the loads not resistive loads, if your meter shows < an Ohm right now you have right now it means you have short circuit. The loads in this case are active loads, I.E. Transistors, IC's, not constant loads so some of the loads may not come into play until they are turned on (or bias on). Those loads will not be able to be turned on by your Ohm meter so the resistance reading should be in K Ohms range at the output of that power supply.
You need to check that lower MOSFET Q508 to see if it is shorted or not by removing L505 to isolate the loads from that Half bridge drive MOSFET's. The MLC caps on the output can also be shorted too if the lower MOSFET tested OK.

[Elwood]

Re: 47LV5400 Component Values and Schematics

That is not how it works in this case, it does not mean you will see 0.12 Ohms at the output because the loads not resistive loads, if your meter shows < an Ohm right now you have right now it means you have short circuit. The loads in this case are active loads, I.E. Transistors, IC's, not constant loads so some of the loads may not come into play until they are turned on (or bias on). Those loads will not be able to be turned on by your Ohm meter so the resistance reading should be in K Ohms range at the output of that power supply.
You need to check that lower MOSFET Q508 to see if it is shorted or not by removing L505 to isolate the loads from that Half bridge drive MOSFET's. The MLC caps on the output can also be shorted too if the lower MOSFET tested OK.

Before posting the last message I cut the trace on the output side of L505. The the short is definitely further down the line. I also removed the heatsink to see if there were any visible signs of damage. Further, I checked all caps on the bottom of the board in that area. C292 was giving about the same reading so I removed and checked it. Still no luck.

[Elwood]

Re: 47LV5400 Component Values and Schematics

Without a schematic or guidance I can't go any further. Now looking for an inexpensive used 47LV5400 EAX63333404(0)

[will62]

Re: 47LV5400 Component Values and Schematics

There are 6 more filtering caps on the back side of the board. The chip probably went before any of them, but you can check them if you want.