Dell Precision 470

[smason]

A friend of mine gave me his Precision 470 to fix.
It's a dual Xeon, in use as a Linux server.

Symptom, power LED is yellow.

I opened it up, and there are several bloated caps on the motherboard.
Mostly the 6.3v ones. Some Nichicon HNM series and a couple of Rubycons.
All of the Matsushita FL and the 3.3v ones near the procs look fine.

I'm hoping the power supply is fine, and it's just these caps.

Tempted to put in some Panny FM and FCs, as I have stock, but I guess I should look up the specs, as it's more critical than the monitors I'm used to using Pannys in.

[smason]

Re: Dell Precision 470

Update 1:
looked at the specs, pannys were a bit lacking in the ripple dept. so I decided to go with Nichicons, added to the order I was about to place anyway.

[smason]

Re: Dell Precision 470

Wow, I forgot how much I hate working on motherboards.
Intersting, the 2 bloated Rubycons off by themselves were very bad 1500uf measured 8uf and 58ohms ESR.

The 3 Nichicons grouped together, 1 bloated - the bloated one was bad, the other 2 measured almost perfect.

Will re-assemble tomorrow and test. <crossing fingers>

[Uranium-235]

Re: Dell Precision 470

remember dells commonly have the positive side marked

[smason]

Re: Dell Precision 470

remember dells commonly have the positive side marked

Yeah, I just barely noticed that in time.

[smason]

Re: Dell Precision 470

Wow, I forgot how much I hate working on motherboards.
Intersting, the 2 bloated Rubycons off by themselves were very bad 1500uf measured 8uf and 58ohms ESR.

The 3 Nichicons grouped together, 1 bloated - the bloated one was bad, the other 2 measured almost perfect.

Will re-assemble tomorrow and test. <crossing fingers>

Got it all back together and.... same problem.
Time to look at the power supply.

[smason]

Re: Dell Precision 470

OK, getting back to this, spent a bit of quality time on it tonight.
Was able to get the power supply to fire up by pulling PS_ON to gnd.
It measures good on all outputs, with a very light load.

So a question. The system has a yellow indicator on the power switch BEFORE you try to turn it on. My understanding is the only thing it sees from the power supply at this stage is 5Vstandby (which is fine, and the motherboard LED is green) and the PS_ON line, which by the way is only 4.8v unloaded.
What would the motherboard be complaining about, the PS_ON voltage being low?

[smason]

Re: Dell Precision 470

Another hour wasted, still dunno wtf is up.
Following the logic of my last post (motherboard only gets 5vstby and ps_on in powered off mode, and the slightly low 4.8v of the ps_on might be doing it,
I connected the power supply, minus the ps_on line, and fed the motherboard the ps_on line from a good power supply, yes with proper grounds etc. Power button still yellow.
disconnected the second supply, and grounded the ps_on line of the main supply, and the supply powers up. CPU coolers come on, but no boot (I don't expect it to boot, as there's probably some more power on logic needed, and it still "thinks" there's a fault <yellow power button>

I measured the 5V-stby it's 5v. So I don't know what the motherboard thinks is wrong.
So now I'm leaning toward it being a motherboard problem.

[Pentium4]

Re: Dell Precision 470

Are you getting a screen, POST, etc? Or is it just a black screen?

[smason]

Re: Dell Precision 470

Are you getting a screen, POST, etc? Or is it just a black screen?

Nothing. It doesn't seem to try to post when I force PS_ON on the PS, but I suspect there's other logic required to get a motherboard to start than just having the supply come on.

[Pentium4]

Re: Dell Precision 470

Yeah. I had a dead server board with some bulged Sanyo caps on it. When I got really close to it, I could smell one of the little IC's. It smelled really burnt, but only when I got my nose really close to it. I'm guessing that is what killed the Sanyo caps. This server would not POST either

[smason]

Re: Dell Precision 470

Now that I think of it, the owner mentioned having some usb issues. Tomorrow I'll check the USB ports and circuitry, maybe something there is pulling a voltage down.

[smason]

Re: Dell Precision 470

Thinking this through a bit more, when you connect AC power to many Dell models (when they're working properly) they DO do a brief power on (fans lights etc.) so it may indeed be looking for some response from something other than just 5VStby.

[Uranium-235]

Re: Dell Precision 470

Thinking this through a bit more, when you connect AC power to many Dell models (when they're working properly) they DO do a brief power on (fans lights etc.) so it may indeed be looking for some response from something other than just 5VStby.

yeah i've noticed that too before. But they usually never 'yellow' button during this activity. USB problems? Sounds to me like the chipset is going bad. There is a chance that the bloated caps over-volted the southbridge, northbridge, or CPU (which BTW, have you tried replacing that?)

wait, cut that, its a fucking xeon (..does research..) yeah 604 Xeon chips

funny, my poweredge 1800 (also dual Xeon 604 /w DDR2 3200) has about the same specs, nothing but rubycons on this board. fucking dell cheapening out

[Nathan]

What it took to fix our Dell 470 motherboard.

I just had a couple days of fun repairing a Dell Precision 470 motherboard and thought I would share what we found with you nice people. (A little late..sorry)

Short version: In my case, the failed capacitors killed the Power Controller IC (IC5) on the motherboard.

Initial symptoms:
The system had a Amber lite on the front panel. The system would not power on at all. When the chassis was opened, we noted the "Aux Power" (amber) and "STR_LED" (green) were illuminated any time the AC power cord was plugged in to the power suply.
Visual inspection revealevd that C149 and C150 had vented.
The power supply was eliminated as possible failure with known good Power supply.

Corrective action:
ALL electrolytic capacitors were replaced. System still had the same problem.
No capacitors measured unusally high ESR or out of tolerance.(except C149 and C150)

We discovered that the Gate on one of the MOSFETs on the motherboard was shorted directly to GND.
The short was eventually traced back to the PWM/triple linear regulator IC on the motherboard. (IC5) Pin 10 (LGATE) was shorted to Pin 9 (Gnd) The part number for this component is HIP6521. This was ordered from Digikey and the IC was replaced. This repaired the motherboard to operational status.

FYI- Observed Normal operation = When AC power is applied the fans spin and The STR_LED illuminate for a moment and then stop until the power button is pressed.
Well wasn't that fun....
Regards,

[smason]

Re: What it took to fix our Dell 470 motherboard.

I just had a couple days of fun repairing a Dell Precision 470 motherboard and thought I would share what we found with you nice people. (A little late..sorry),

Hi, welcome to Badcaps. Not too late, I haven't scrapped it yet.

Thanks for the info! I'll definitely check that out when I get a minute.

Been a busy 2 weeks here, with flooding, no power for a week at work, then a record humidity day that caused an A/C unit to belch water into a server rack.
Totally fried a Dell PowerEdge 1950 (will post a thread with crispy photos later)

[smason]

Re: Dell Precision 470

Well, it's not that chip but it may be something in the neighborhood.

Pin 6 measures 1.8 ohms to ground. Pulled the chip, chip measures ok, pin 6 still 1.8ohms to gnd on the board. Pulled the FET that's connected to pin 6, same.
There are 2 bypass caps and 2 electrolytics all in parallel that all read 1.8 ohms. I pulled one ceramic, it's fine, the other is on the top side between the electros, so I'll need to pull them all to check the ceramic. Or it could be anything else

[Nathan]

Re: Dell Precision 470

F.W.I.W.- I measure ~11.2 ohms from pin 6 "PHASE" to Pin 9 "PGND" on IC5 (Intersil- HIP6521) on a working 470 motherboard.
(with or without CPU installed)

[smason]

Re: Dell Precision 470

Thanks, that's helpful.

[Per Hansson]

Re: Dell Precision 470

If you want i have a recapped 470 mobo that I don't use, drop me a PM if you are interested.

Photots of it here: https://www.badcaps.net/forum/showthread.php?t=5974