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Old 02-02-2017, 05:17 PM   #1
Spork Schivago
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Default Suggestions for an HP M3970CM repair.

Hello,

I have an HP M3970CM motherboard here. There's a four pin header that says PUMP. The customer moved the motherboard to a new case. The power supply has a two pin header. For some reason, he thought the two pin header plugged into the four pin header. It killed the motherboard. When I manually try jump starting it (shorting the pins on the panel header), the fan will almost start. It'll jump a little. He fried something out on the motherboard and I was hoping someone might want to give some suggestions as to what he might have fried.

I was thinking he might have actually fried the CPU. I've checked the various fuses. There's three caps near the 4-pin header. I pulled them, they're good. It's a socket AM3r2 and I don't have a CPU I can try in there. Any suggestions? I'm thinking of just telling him he needs a new board, but the ones I've found are a bit pricey.

Thanks!
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Old 02-02-2017, 05:31 PM   #2
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Default Re: Suggestions for an HP M3970CM repair.

have you got a picture of it ?
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Old 02-02-2017, 06:13 PM   #3
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Default Re: Suggestions for an HP M3970CM repair.

I'll upload them now, but I don't know if they'll do any good. The one that shows the header with the word PUMP is where he plugged the power into it. I'm thinking it might very well be the CPU that's dead. I can't really think what component(s) would fail that would make the board act this way (minus the fuses that I've already checked). The CPU fan just jerks for a second when I try turning it on, the power supply doesn't turn on at all. If I only plug 20 of the power supply pins into the motherboard, we get a little action, but when I plug in those extra 4 pins, nothing.

Hopefully someone with a little more knowledge will be able to give me some test points on the board or something to check for various voltages or something.

Thanks petehall347.
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Old 02-02-2017, 06:28 PM   #4
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Default Re: Suggestions for an HP M3970CM repair.

be good to at least know which pins were shorted or what sort of power was put into the board in the wrong place and access to a schematic / service manual .
knowing what pump does would be a starting point .. i looked for a manual but found nothing .

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Old 02-02-2017, 06:47 PM   #5
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Default Re: Suggestions for an HP M3970CM repair.

The pump header is to power a pump for liquid cooling. This person didn't use a liquid cooling setup. I can put a DMM to the power supply plug he had plugged in there, but I'm guessing it was 12VDC. Notice the cap next to that one heatsink. It's discoloured, but tests fine. There's a few components that are discoloured around that silver heatsink. Is that the AMD 970 chipset under there? I see the AMD 970 chipset uses a SB950/SB920 southbridge. Is that built into the AMD 970 or something? I couldn't find a replacement AMD 970 or maybe I'd attempt to replace the one under the heatsink (if that's what's under there).

Here's a link to the manufacturer's website for this PC:
http://support.hp.com/us-en/product/.../model/5296860

It lists the board as an Angelica2 M3970AM, however, the sticker on the board says M3970CM. From what I can tell, the 2nd to last letter is maybe just a revision. There's an AM, BM, CM (maybe more?).
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Old 02-02-2017, 06:48 PM   #6
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Default Re: Suggestions for an HP M3970CM repair.

If I had a compatible processor, I'd put it in, just to test if the CPU is fried or not, but I don't have any AMDs that new. Also, I doubt it'd be any help, but I believe Gigabyte makes the board.

I'll add that I can power parts of the board manually with my programmable PSU, but I don't know if that's a good idea or not. Would that damage anything if I only provide 5VDC to the PSU connector? Also, I'd be flying pretty blind like. When the PSU kicks off, I'm assuming very little of the board is getting power. I could force some power through there, but I figure if the PSU won't stay on, it's probably for a good reason. Maybe there's a short somewheres. It's a multi-layered board so I can't just follow traces.

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Old 02-03-2017, 02:07 PM   #7
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Default Re: Suggestions for an HP M3970CM repair.

wondering what would happen without cpu installed ...
should it give a series of beeps like it would if no ram installed ...
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Old 02-03-2017, 02:36 PM   #8
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Default Re: Suggestions for an HP M3970CM repair.

If that PUMP header is supposed to supply power it will probably have a MOSFET or regulator or something which is supposed to control it.

When he applied power to it instead, probably that part has blown from the reverse voltage and gone shorted. That will be why the board doesn't start up - the PSU or the board sees the short and shuts down again straight away to stop things catching fire.

Unless the CPU supplies power to the PUMP connector, I doubt it has been damaged.


Without a schematic it will be hard to figure anything out though. You could check the assorted SOT-23 devices nearby to the connector and maybe the 8-Pin chip at the end of the PCI-E slot for shorts. It's possible they are responsible for the PUMP control, since they are nearby - although it's not guaranteed.

Do you have a pinout for the PUMP connector and do you know what he plugged in where?

If you are really unlucky he may have sent 12v into a 3v or 5v logic input (for reading pump RPM or temperature or something) and blew the SIO chip or such.
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Old 02-03-2017, 02:53 PM   #9
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Default Re: Suggestions for an HP M3970CM repair.

Quote:
Originally Posted by Spork Schivago View Post
If I only plug 20 of the power supply pins into the motherboard, we get a little action, but when I plug in those extra 4 pins, nothing.
Which 4 pins? 12v AUX for CPU or the detachable 4-pin connector of a 24-Pin main ATX connector?

If you think the CPU is shorted, try running without the CPU. If the board turns on (it won't POST obviously) then maybe it is the CPU.
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Old 02-03-2017, 07:58 PM   #10
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Default Re: Suggestions for an HP M3970CM repair.

Quote:
Originally Posted by petehall347 View Post
wondering what would happen without cpu installed ...
should it give a series of beeps like it would if no ram installed ...
Without a CPU installed, I'd think it'd do what it's doing now, maybe minus the fan jerking like it is. I would think without the CPU, the system would be officially dead. Hitting the power button wouldn't even turn on the PSU, that'd be my guess. But it's just a guess. Tomorrow, I'll setup an experiment with a known good system and give it a try.

Thanks for the idea. For what it's worth, I'd like to add that one of the first few tests I ran was removing the RAM and trying to turn it on, to see if it'd beep. It didn't. That's when I started thinking maybe a fried CPU.

I found another broken board on e-bay. The guy selling it wants around 20$. He says as-is but answered my questions. All caps are flat and he says he wants to say the person he got it off of said the video didn't work. These boards don't have on-board, so maybe that board isn't dead, or if it is, maybe it's a bit easier to fix than this one. The only problem is no CPU. Being an AMD 6-core, I bet that CPU goes for at least 100$. I could buy that 20$ board and nothing might not be wrong with it at all, but I might never know because maybe the CPU in this one is fried. It's around 220$ for a "factory refurbished" working board.
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Old 02-03-2017, 08:05 PM   #11
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Default Re: Suggestions for an HP M3970CM repair.

Quote:
Originally Posted by Agent24 View Post
If that PUMP header is supposed to supply power it will probably have a MOSFET or regulator or something which is supposed to control it.

When he applied power to it instead, probably that part has blown from the reverse voltage and gone shorted. That will be why the board doesn't start up - the PSU or the board sees the short and shuts down again straight away to stop things catching fire.

Unless the CPU supplies power to the PUMP connector, I doubt it has been damaged.


Without a schematic it will be hard to figure anything out though. You could check the assorted SOT-23 devices nearby to the connector and maybe the 8-Pin chip at the end of the PCI-E slot for shorts. It's possible they are responsible for the PUMP control, since they are nearby - although it's not guaranteed.

Do you have a pinout for the PUMP connector and do you know what he plugged in where?

If you are really unlucky he may have sent 12v into a 3v or 5v logic input (for reading pump RPM or temperature or something) and blew the SIO chip or such.
Thank you Agent24. Would that book you recommend go into this kind of stuff? If so, perhaps I should purchase it after all. You've given me a good starting point. I didn't think any of those SOT-23's had anything to do with that header. I don't have a pin-out for the header, but I haven't looked. It's a four-pin header, he plugged a two-pin connector into it. I don't know which of the four pins he had the 2-pin connector on, but I could take an educated guess. When I got it, he had messed it with it more, so there's a chance he just went through and tried every combination.

There's 7 little SMD components right behind that 4-pin header. They might be hard to see in the picture. They're extremely hard and I'm certain some of them are dead. It might be impossible for me to replace those. I could remove them, but I might not ever get them back on, because of how small they are.

For those SOT-23's, are you talking just about the ones around that 8-pin chip or are you talking about all the SOT-23's that are anywhere near the 4-pin header? I have a device that will allow me to check those SOT-23's, but I have to remove them. Is there a way to test them for a short while they're in-circuit still or do they have to come off? For the 8-pin, just take a DMM and check the continuity between all the various pins? Thanks!
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Old 02-03-2017, 08:08 PM   #12
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Default Re: Suggestions for an HP M3970CM repair.

Quote:
Originally Posted by Agent24 View Post
Which 4 pins? 12v AUX for CPU or the detachable 4-pin connector of a 24-Pin main ATX connector?

If you think the CPU is shorted, try running without the CPU. If the board turns on (it won't POST obviously) then maybe it is the CPU.
I should have specified, the detachable 4-pin connector for the 24-pin ATX connector. That one. Yesterday was the first night I got more than 4 hours or so of sleep. Last night, I got around 4 again. The baby been keeping me awake, I don't remember exactly what it did, but I'll plug it in tomorrow. I want to say I tried with the 4-pin CPU power unplugged and it didn't do anything, but I'll try removing the CPU, I'll try the various connectors for the PSU, I'll try all that.

Are you sure if the CPU is dead, the PSU will at least turn on if the CPU is removed?
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Old 02-03-2017, 09:03 PM   #13
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Default Re: Suggestions for an HP M3970CM repair.

With the CPU completely removed, I get nothing, even with the 4-pin from the 24-pin ATX connector removed. With the CPU in, I get nothing, not even the jerk that I was getting, but I remove the 4-pin from the 24-pin ATX connector, then the PSU fan will spin for a second. It'll go around probably 10 full rotations, no noise or anything, slower than it should be. I've tried with and without the 4-pin CPU power connector. That doesn't seem to matter.

The only way I can get the PSU fan to move is by shorting the two pins on the front panel header. The CPU fan doesn't move at all, ever.

It's really dirty, the whole board. The person smokes and I think this is smoke residue, mixed in with dust. It's very hard telling if a component looks burned out or if it's just dirty. I have some distilled water. I wonder if it'd be wise to try and wash it in the distilled water to clean it up a bit.
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Old 02-03-2017, 10:11 PM   #14
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Default Re: Suggestions for an HP M3970CM repair.

A working motherboard *should* start up and run (fans spinning) without a CPU, it just won't beep or do anything else, because there's no CPU to run the BIOS code.

A shorted CPU would prevent the board from turning on, but the fact yours doesn't start up even with the CPU removed shows its most likely the board itself which is dead. Given what the guy did to it, that makes sense.

The book I mentioned would be a good read for motherboard repair in general - but it won't really help in this case because we don't have a schematic for the board.

Distilled water is good for the final rinse off, but you will need some kind of cleaner too. Check the sticky here: http://www.badcaps.net/forum/showthread.php?t=1463
Some people also run boards through a dishwasher, or so I've heard.

You can test all the SOT-23 components near the header without removing them, just check there are no shorts between the pins. You might get lucky.

If you can find which rail the short is on (check all the rails resistance to ground from that 4-pin connector on the main ATX, since it acts differently, the problem circuit may be powered from that connector) you might be able to apply power externally and find out which part heats up.
Use current limiting so it heats rather than smokes (and you can still read the label). There's the trick of putting alcohol on the board and seeing where it evaporates first. That will show you what is getting hot.

Other than that, without a schematic, you're pretty much out of luck, I'd say.

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Old 02-04-2017, 05:02 PM   #15
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Default Re: Suggestions for an HP M3970CM repair.

I took the DMM and set it to continuity. I checked the resistance between all the SOT-23 pins, there was always continuity, but nothing that says anything like 0 ohm. I had a couple that showed something like 14Kohm or so. I could check again if you think that isn't right.

I took the DMM and did the same with that 8-pin IC and I want to say there was just two pins that showed 0 ohm. I'll try finding a datasheet for it, but I'm thinking those two pins might be GND. If it sounds like the CPU is good, that's kind of good news. It makes buying a new motherboard for him not so nerve racking. I always hate saying okay, you need <blah> and when <blah> comes, it doesn't fix the problem. Most of the time, there's a way to check <blah> to see if it's bad or not. Sometimes, it's just a educated guessing game. It's most likely it's just the board and not the CPU. Thanks!!!!
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Old 02-05-2017, 02:59 AM   #16
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Default Re: Suggestions for an HP M3970CM repair.

Sounds fine to me. Only a dead short (0 ohms) would cause the system to fail start-up.

I wouldn't expect an 8-pin chip to have two ground connections. That sounds a bit funny. You could investigate that, although it may be nothing to do with the problem. What is written on that chip?
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Old 02-05-2017, 12:43 PM   #17
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Default Re: Suggestions for an HP M3970CM repair.

I've seen ICs, like dual 555-timers, that have essentially two ICs built into one chip. I was thinking it could be something like that.
Code:
AS358M
G1 (maybe?)
217JJ3
https://www.diodes.com/assets/Datasheets/AS358_A.pdf

It does not have two GNDs. I'll double check the continuity and make sure I'm remembering it correctly.

Each pin of that 4-pin pump header has an SMD component. I'm wondering what would happen if those SMD components would have shorted out. I'm thinking of just removing them. The 4-pin PUMP header wouldn't work, but if they're faulty (and I'm assuming at least one is), maybe they're preventing the PC from starting and removing them will allow it to start up. It's very hard to check the continuity of them and read any markings, if there are any markings, because of how small they are.

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Old 02-05-2017, 12:57 PM   #18
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Default Re: Suggestions for an HP M3970CM repair.

Here's the continuity of the components next to the header. I'll write what I think they are and then the continuity I measured:
Code:
black SMD resistor: 8.17 Kohm
black SMD resistor: 100 ohm
black SMD resistor: 3.91 Kohm (but started at 3.67 Kohm and counted up until it stopped at around 3.91 Kohm)
SMD capacitor: 3.50 Kohm (just counts up and up and up)
black SMD resistor: 0.0000 ohm (could this be causing the issues?)
black SMD resistor: starts at 5 Kohm and counts up to around 6.40 Kohm
SMD capacitor: starts at 9 Kohm and counts down!!!
I guess I'm going to remove those SMD components, if I can. What can it hurt at this point? One of them doesn't look like it's in good shape at all (the SMD capacitor looking one). It appears to be crumbling.

I went back to the 8-pin IC and double checked. I must have been remembering it wrong. There are no two pins that show 0.0000 Ohm resistance, but there's one that shows 0L (Overload, infinite resistance), that's what I must have been remembering.
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Old 02-05-2017, 05:58 PM   #19
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Default Re: Suggestions for an HP M3970CM repair.

Removing them didn't make a difference. I think we're just going to call this board bad and try to find a replacement. Without a schematic, it's more or less a guessing game.
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Old 02-07-2017, 06:28 PM   #20
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Default Re: Suggestions for an HP M3970CM repair.

what does the 2 pin header on the power supply look like? never heard of any standard psu connectors that are 2 pin. did u try using another of your own psu or the same psu that came with the customer's system to power the board? your posts arent clear about this. i have a feeling the psu may be fried instead and cant start up, not the mobo. just need to know what kind of a connector that 2 pin psu connector is to prove or disprove this feeling.

u better test the psu as well to make sure its working. dont want the customer to buy a new board and it doesnt work just because the psu failed.

just wish oems made their stuff idiot proof so the wrong connector doesnt get plugged into the wrong header! but why would u want it to be idiot proof when oems dont even want ppl messing around with their hardware? and so i dont get upset when ppl dont make 4 extra pounds of e-waste by trashing a board with good caps on it!

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