Dell T5500 m/b part's list - L114 parameters

[beta5500]

New on this forum. Wandering if anyone knows where to find Dell T5500 motherboard part list, specifically I'm after inductor L114 - inductance & current. It got sizzled. Just to put in context - guessing some members could be suggesting to get new m/b - I'm retired and enjoy warming up the soldering iron from time to time, while the eye can see and the hand steady, to keep the brain ticking.

All other elements in that circuit look & test OK, after turning on LED 1 & 2 turn green, than shut down. PSU tests fine.
Your help appreciated

 

[notb]

I doubt this is the best place you could have asked this question.

Have you tried Dell's community forum?
https://www.dell.com/community/Dell-Community/ct-p/English
People there know Dell's stuff very well. Dell employees are also present.

 

[beta5500]

Thank you for your time taken to respond.
Following your suggestion now

 

[micropage7]

New on this forum. Wandering if anyone knows where to find Dell T5500 motherboard part list, specifically I'm after inductor L114 - inductance & current. It got sizzled. Just to put in context - guessing some members could be suggesting to get new m/b - I'm retired and enjoy warming up the soldering iron from time to time, while the eye can see and the hand steady, to keep the brain ticking.

All other elements in that circuit look & test OK, after turning on LED 1 & 2 turn green, than shut down. PSU tests fine.
Your help appreciated

maybe you can put the pic in here so people know what it is

 

[E-Bear]

New on this forum. Wandering if anyone knows where to find Dell T5500 motherboard part list, specifically I'm after inductor L114 - inductance & current. It got sizzled. Just to put in context - guessing some members could be suggesting to get new m/b - I'm retired and enjoy warming up the soldering iron from time to time, while the eye can see and the hand steady, to keep the brain ticking.

All other elements in that circuit look & test OK, after turning on LED 1 & 2 turn green, than shut down. PSU tests fine.
Your help appreciated

read this. https://www.dell.com/community/Desk...ng-T5500-motherboard-part-number/td-p/5091740

 

[beta5500]

micropage7 - pic enclosed (apology for poor quality). What's left of it is the black-ish 5-star on the right, while its 2 still healthy "cousins" are on the left, approx dimensions 4 x 1.5 x 0.5 mm . The space between them appears to have been made ready for use but left unfilled.

E-Bear - checked that thread, thank you. It's about m/b version number, not individual parts (components) on it.

 

[Caring1]

I'd suggest picking up another Motherboard for spare parts or applying power to the existing motherboard and testing those two neighboring units with a multi-meter.

 

[silentbogo]

micropage7 - pic enclosed (apology for poor quality). What's left of it is the black-ish 5-star on the right, while its 2 still healthy "cousins" are on the left, approx dimensions 4 x 1.5 x 0.5 mm . The space between them appears to have been made ready for use but left unfilled.
View attachment 120505

E-Bear - checked that thread, thank you. It's about m/b version number, not individual parts (components) on it.

Those look similar to laptop DC input filtering. If all you want is get it running, I suggest to do the following:
1) Remove the rightmost choke and possibly the other ones if they are fried (those should have a very low resistance, if you check w/ MM)
2) Check if there is a short on the output side (no short circuits). Do it after removing all dead inductors
3) If you don't have a donor board or parts source, then you can try and replace those with regular wire jumpers. You will not have any input filtering, but the board should work.

If you have a chance, make a larger picture of this area, so I can check which power rail that is.

EDIT: if you have a local parts retailer or any type of donor board with known parts, you may try something like HCB2012-series inductors.
http://www.coils-tech.com/upload/file/Datasheet/HCB2012_Series.pdf
These are quite common. HCB2012-121T20 should get the job done. Worst case scenario - it'll blow up like the other one and you'll lose a 25c worth of parts ))

 

[E-Bear]

micropage7 - pic enclosed (apology for poor quality). What's left of it is the black-ish 5-star on the right, while its 2 still healthy "cousins" are on the left, approx dimensions 4 x 1.5 x 0.5 mm . The space between them appears to have been made ready for use but left unfilled.
View attachment 120505

E-Bear - checked that thread, thank you. It's about m/b version number, not individual parts (components) on it.

With the motherboard version number you get exactly what ypu need to search for and get the plans

 

[beta5500]

Caring1 - tested the two inductors adjacent to the sizzled one (still in-board) - they appear OK, but since my last post discovered a cracked and shorted SMD capacitor nearby, so will do more checking tomorrow (night time in my part of the world now). Thank you for help.
Went on a shopping spree & picked a dead T5500 for about 13$ (no RAM, no disk) and a working one for about $90 (E5520, 6x 1GB RAM).


silentbogo - your suggestions much appreciated, filled big gaps in my knowledge.

On your point 3 - I didn't try because I didn't think it could work by just jumping the space (lesson learnt, again, presume nothing). The discovery of cracked and shorted capacitor (1 of 3 in parallel) prompts me to do more careful checking.
Now with 2 other units (both with m/b version D883F, which is earlier - after quick check there doesn't appear to be any difference in the area of interest) I should have enough to replace all faulty parts.

Will make a better pic of a larger area tomorrow in daylight hours & post.
Once again, your comments were of great help.


E-Bear - searched the net for the plans, circuit diagrams and list before posting here, alas, no luck. Still awaiting response from Dell Community Forum.

 

[silentbogo]

The discovery of cracked and shorted capacitor (1 of 3 in parallel) prompts me to do more careful checking.

Also don't forget to check that rail after you remove the cap. Just in case.

 

[MrGenius]

With the motherboard version number you get exactly what ypu need to search for and get the plans

Out of genuine curiosity...

Search as in how?

Get as in where?

I've only ran across 1 complete motherboard schematic online...EVER! They seem to be rarer than hen's teeth. You make it sound easy. Is there a secret?

EDIT: BTW a quick google search with the version number from that thread you linked yielded absolutely nothing.

 

[beta5500]

silentbogo - thank you for the hint. The pic of a larger area attached, as per your earlier request.

The dead m/b that I was going to use as a donor showed the inductor intact, but the tester disagreed, showing an open circuit (on 200 ohm range). Confirmed by a 2nd M/M. But noticed a different SMD capacitor cracked within the parallel-trio, and short confirmed. So, we have 2 different m/b versions with essentially the same damage.

Not believing in coincidence, after some reading about the aging process of ceramic capacitors, I'm now inclined to think that it was the weakest within the capacitor's triplet that failed, with the resultant short causing fatal damage to the inductor - same story in both m/bs.

Quickly ordered a tape of 10uF/25V SMDs, but then started thinking about why the "triplet" instead of just a single cap? Triple points of failure, triple soldering, higher overall cost. Found many more of those on the m/b (some could be seen in the pic, south of the cpu socket), as well as many "twins".

At this stage didn't pull a healthy nearby inductor (they all show about 0.2 ohms in-board, don't have an accurate low range resistance meter) from dead m/b, as if the above thinking proved correct, then both non-working m/bs should be easily recoverable. Might first try some inductors from dead hdds, to see if that works. If not, then see if it's worthwhile to pull L114 from the working m/b to test inductance.

Once again, thank you all for hints and help.

 

[silentbogo]

At this stage didn't pull a healthy nearby inductor (they all show about 0.2 ohms in-board, don't have an accurate low range resistance meter) from dead m/b, as if the above thinking proved correct, then both non-working m/bs should be easily recoverable. Might first try some inductors from dead hdds, to see if that works. If not, then see if it's worthwhile to pull L114 from the working m/b to test inductance.

Oh... all of that damaged stuff is just EMI filtering on +12V_EPS. Basically you can remove all damaged caps, replace all chokes with big-ass wire jumpers and call it a day. It should work just fine. That's one of the examples of "over-engineering", where an additional feature introduced yet another point of failure. Gotta love those.
You can even replace all 3 ceramic caps with a single 47uF tantalum and it will be much better/sturdier than before.

Another thing to check is those darkened caps around PWM controller. VRM by itself looks perfect, I doubt any damage went beyond the filtering stage.

 

[beta5500]

The darker SMDs are actually inductors (too hard to see in the pic - they are prefixed with "L") and measured in-board they had ~0.2 Ohms.

Followed your advice on a single cap, but decided to stay with the inductor, for its usefulness (perhaps) as a fuse, if nothing else.

The first m/b was easy - after replacing the faulty parts - Power ON, and it started as if nothing was ever wrong with it. Cautious not to call victory too soon I subjected it to a 7 day marathon under near full load, which it passed. Since then it has been under routine use - all as expected.

But the 2nd m/b (that's the one pictured above) - a very different story.
Replaced parts, checked soldered connections - OK, rails - OK, only 1x 1GB RAM, power ON, after Dell logo went into BIOS - all normal, saved BIOS, power down. Populated RAM with 3x8, power ON, BIOS again - all OK, out of BIOS with restart, and, fault 1-2 blink and s/d. Tried Power ON again - fault 1-2 and s/d.
After some thinking decided to return to LKGC with 1x1GB. Was able to get into BIOS again, but on exit & restart - fault 1-2 & s/d. Thinking maybe cold good, warm faulty left it without power for an hour, then for a day, still fault 1-2.
Pulled out PSU, de-dusted, checked - all OK.
Pulled out m/b for more checking and spotted a tiny patch of greenish patina on a small SMD cap just below the faulty ones. When tried to scrape off the patina, one side on the cap has moved, exposing corroded pad and almost completely corroded metal on the cap, but, enough was left to measure the capacitance. Cleaned all and replaced (it looks like some kind of corrosive liquid was splashed through the front grill). Connected all, Power ON, fault 1-2 again.
I am thinking about feeding the CPU rails from 2 separate PSUs, via a current limiting (18A - that's what's printed on Dell PSU) resistance of around 0.7 Ohm to force the power to stay on, and search for the problem.

Is there any easier way to find the offending circuits/parts ?

Once again, many thanks for help, without which I wouldn't be able to get this far.

 

[silentbogo]

The darker SMDs are actually inductors (too hard to see in the pic - they are prefixed with "L") and measured in-board they had ~0.2 Ohms.

No, I mean the actual caps near CPU PWM controller (C1887 or something like that, and the nearby ones). Those have darkened solder and slight solder bulging, which usually means overheating. Caps may look OK, but that's what I usually see on moisture-damaged laptops all the time.

Is there any easier way to find the offending circuits/parts ?

Just ye olde multimeter and random poking on all voltage rails is a good start. Unlike Optiplex and other consumer PCs, this one has more specific failure codes. 1-2 is a general power failure, e.g. one of the PWRGD signals is missing at startup. Start with measuring all major rails at startup (CPU, RAM, NB/SB, +5VSB, +3VSB, +5V and +5VUSB, BIOS voltage etc), if all is good, then start checking PWM controllers and any available testpoints related to any PWRGD or PWROK signals (very hard and time-consuming without schematic). Could be anything from malfunctioning PWM controller, to once again some bad caps or tiny SOT23 transistors, or even a corroded trace.
The first place to look is definitely the one I mentioned above: CPU VRM controller, nearby suspicious caps and resistors.

 

[beta5500]

Thank you for prompt response and extra comment about darkened caps - will focus on those. Didn't realize overheating can accelerate the corrosion process so much.

Also found some corroded traces (perhaps caused by the same liquid splash I mentioned earlier), some quite severely, but they all checked OK. Looks like this m/b might have had multiple causes contributing to failure.

Will follow your suggested order of checking, and then perhaps try to revive an old T5400 that has been sitting dead for over a year.