Motherboard burn out

Hi again. Still curious as to what this chip is. I have attached a pic with blown fuse..chip..? I may have to zoom further to read number but with a little sleuthing I might be able to find this part.

I am totally brand new at electronics but quite interested if anyone has any ideas on this I would love to hear.

Thanks for any info,

Jack

Given that it's a 2-pin part, my guess is a diode.  A close-up look at them they are marked like diodes.

Thanks very much for your reply gunrunnerjohn. I'll see if I can track one down around here. Maybe off an old computer board if not new supply.

Might be that's only thing wrong with this one. Being curious opens new doors lol.

I couldn't find the E3 marking in my index for a 2-pin part, so I'm not sure what it is.  E3 referenced some 3-pin diodes...

Is it burned up or just flux.  Hit it with a tooth brush to see if it cleans off.  G

Put some alcohol on the toothbrush for better cleaning results.

@gunrunnerjohn posted:

I couldn't find the E3 marking in my index for a 2-pin part, so I'm not sure what it is.  E3 referenced some 3-pin diodes...

John I looked through a few old books and found the E-3 as a diode but further checking as no longer in production

Hey thanks for all the info. I grabbed the toothbrush and isopropyl alcohol and scrubbed it up. Looked brand new. Upon real close inspection it still looks like it could be blown. Sure a lot tougher to tell bad ones when cleaned up. So, inspect very carefully first and then clean up and dial down to your suspicious ones.

I'm including another photo as good as I can get with my Galaxy S21! I still suspect faulty chip here.

Looks fine to me, but do you have VM.  Do a diode check on it.  If it was shorted it would be burned or burned off. Plus that has nothing to do with your smoke issue.  G

Very good thought GGG. I just now checked them both. Good one shows .0L one way and .001 the other way.

Suspect one shows .072 one way and .064 the other. Bingo!

You're right as it has nothing to do with my smoke issue but everything to do with the wire on bottom of fan shorting out on frame! You should have heard it sizzles and smoke then. Wire smoke not diesel smoke!

Thanks again for all your interest.

That is not uncommon in the circuit for some diodes.  Your not just measuring the diode.  So if you have a good board compare how it reads.  It may be the same.  G

AAMOF, it is normal for that board, I checked a working board and one of those diodes appears to be directly shorted.

The IC directly above the diode looks blown also.

I feel this kind of went astray trying to chase down components we "think" were damaged by visual indication- very hard to do in SMT components and being honest, not always the most effective method. I'm saying that because we know the exact event the caused the issue- the fan was shorted to frame. In that event 2 things likely happened. #1 AC voltage was applied and was backfeeding up the P5V line that powers the fan and the tachometer sensor PCB- 2 things known to use the 5V DC circuit and again would be really unhappy with AC applied. We then also assume the N channel MOSFET on the low side of the fan motor to (DC PCB GND) likely might have blown from the AC current as well.

So realistically, we might have killed 2 major board functions. We might have damaged the P5V regulator section and anything else using that DC 5V rail. Obviously it took out the external tachometer board, but measuring to see if we still have 5V present might be a better status or troubleshooting. I personally do not know what all ICs are involved in this portion of the circuit.

The other function likely killed is the FAN MOSFET. https://ogrforum.com/...4#133615320937078554

@gunrunnerjohn posted:

No, the smoke fan FET is Q209, and it's a NTJD4105CT1G, available at Digikey.

Also, this topic https://ogrforum.com/...6#163461606365601006

@gunrunnerjohn posted:

Not something you want to attempt to fix if you have to ask that question!   It's a tiny surface mount component Q209 on the bottom of the PS/3 board.  It's 2mm x 1.25mm in size, and needless to say, soldering the six pins is a challenge with anything but the finest tip iron or a hot air tool.

Again, I'm not saying other components are not burned or failed, but at the same time, I'm trying to make what I felt was a more sensible testable approach.

#1 test if P5V rail is actually a stable 5V DC to PCB ground. Again, this is because we know we shorted the fan P5V lead either directly or through the motor to AC potential- we may have killed or damaged this DC rail voltage and the regulator controlling it, and any other components that were on this rail.

#2 likely replace the failed smoke FET, Q209, a NTJD4105CT1G- which also would have likely failed in the event- again AC frame passing through the motor or direct short to frame. FETs tend to fail shorted first, then eventually burn open circuit in really bad situations.

Using this diagram of the PS3 Diesel board outputs, again we are looking for 5V DC between grey P5V outputs and PCB GND typically purple wiring.

Yes Chuck, it did look suspicious. As to the other E3's, there is 7 on the board and only 1 that reads high both ways.

When the board is faulty, pop off the suspects and use multimeter to check offboard I guess? At this stage I've nothing to lose and experience to gain lol.

With stronger magnification there should be better ID? I have probes out to different electronic suppliers, I'll keep you posted.

@Jack VSLR posted:

Yes Chuck, it did look suspicious. As to the other E3's, there is 7 on the board and only 1 that reads high both ways.

When the board is faulty, pop off the suspects and use multimeter to check offboard I guess? At this stage I've nothing to lose and experience to gain lol.

With stronger magnification there should be better ID? I have probes out to different electronic suppliers, I'll keep you posted.

Yes, in many cases, because the control circuit is complicated (example let's say there are external snubber diodes in parallel to an FET) then test results on the board may not be obvious as to what component is bad.

At the same time, due to the small nature of SMD components, resoldering them after removing them generally is not good. So if you remove the component, you probably are replacing it with new.

Again, sorry if I'm coming into this late, I'm just trying to prevent the shotgun parts cannon approach to fixing a board.

This is also where the MTH PS3 board tester can be useful (I don't have one myself sadly just being this late in the game), but even an upgrade kit wiring harness and remove the tach sensor so you don't damage it if the 5V rail is wonky or out of specifications.

Again my thought is, figure out how bad of shape we are in. If 5V rail is damaged, the board might not be repairable or not worth the effort.

If the 5V rail is intact, maybe you get lucky and it's just the smoke fan FET.

Awesome Vernon, for sure that's a great approach. I like the logic. I'm pretty sure it was the green wire that shorted on frame. Makes sense to trace that back.

Yes, I did have to replace speed reader too.

Also, the 2 topics I posted in the earlier reply, technically they were 2 different components and aspects of a smoke failure (smoke heater control VS fan control)

In this topic, the heater MOSFET a larger 8 pin device (Q227 is the smoke heat FET, NTMS5835NLR2G) is what actually failed and was because the heater wiring was effectively shorted https://ogrforum.com/...4#133615320937078554 That said, that just happened to be where john kindly mentioned the smoke fan motor FET part number.

Then further searching to show the location of the actual smoke fan motor MOSFET (Q209, a NTJD4105CT1G) was more detailed in this thread again, huge thanks to gunrunnerjohn

https://ogrforum.com/...6#163461606365601006

You can't compare readings on the same component on different parts of the board.  You missed the point of it is part of an integrated circuit.  You don't know what else you are measuring.  You need to compare an apple to an apple.  Same component and location on another KNOWN good board.  Only way you can tell if a reading is normal in that spot.  Otherwise remove it from PCB and test it.

If you short a DC wire 5V/Ground on a PS-3 board to AC frame you short more than just the 5V source.  Every component that uses 5V or PCB ground is exposed to AC voltage and can be damaged.  So the main processor and other chips get destroyed.  PS-3 does not handle that well.

So does this board work with the exception of smoke?  If not, it is toast most likely.  If it does work with exception of smoke, replace smoke components and hope it is restored.  G