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NoelC

Long Term System Stability?

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NoelC    1,371

Funny you should mention electrolytic caps...  My son and I took apart our recently non-functional Precision 470 workstation this evening and wouldn't you know; 3 of them have let out the magic stuff from inside.  Parts on order...

 

-Noel

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NoelC    1,371

Yep.  Rubycon 6.3v 2200 uF and 1500 uF with the "K" scoring on the can end.

 

Bad470Caps.jpg

 

Bad470Caps2.jpg

 

-Noel

Edited by NoelC

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TELVM    172

^ Not a very common sight to watch Ruby MCZs (one of the best ever brands and series of lytics for mobos) puking their guts that way. Guess they must have been subjected to tons of heat.
 
I'd suggest improving case ventilation radically with more fans, and placing DIY heatsinks on those three mosfets close to the damaged caps to unload heat from the area:
 

UrvHeemD.png

  • Ruby MCZ 1500uF 6.3V are 1960 ripple / 0.016 ESR

It might be difficult to get brand new Ruby MCzs nowadays. A good replacement would be Nichicon HN (specs)

  • Nichicon HN 2200uF 6.3V 10x20: 2900 ripple / 0.010 ESR
  • Nichicon HN 1500uF 6.3V 10x16 (bit taller than the 10x12.5 MCZs): 2280 ripple / 0.011 ESR

^ Both have slightly higher ripple tolerance and slightly lower ESR than the Rubys, which is good.

Edited by TELVM

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NoelC    1,371

There was a lot of dust build-up - almost like a blanket.  I suspect neglect was the culprit.  Plus the placement of these as related to the processor fan shrouds seems to be such that air does not flow strongly over them.

 

Thanks for the tips.  I didn't put much effort into getting exact brand replacements, since these had failed.  Maybe I should rethink that.

 

Since I did not realize the minor specs would matter, I had already ordered several replacements (not expensive) based on only the specs (same uF, V, and 105C), I did not consider the additional data you noted.  Should I just ignore the first order (not expensive) and seek better specs?

 

Those that I ordered are Illinois Capacitor JWT 1500 uF 6.3v 105C Radial and Panasonic FJ 2200 uF 6.3v 105C Radial ("Low ESR").  I'm looking for the additional specs now.  One thing that has me initially concerned is that I don't see a "JWT" moniker listed at all at Illinois Capacitor.

 

-Noel

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TELVM    172

Beware that those caps are filtering the VRM output to the Northbridge, which is mission critical for stability, and that's why top-notch and expensive Ruby MCZs were used there.

 

They shouldn't be replaced with just any cap of same uF and voltage, they need to be of same or better ripple tolerance and ESR (higher ripple is better, lower ESR is better).

Can't find specs of Illinois caps 'JWT' series.

The Panny FJ 2200uF 6.3V 10x20 are 2550 ripple / 0.013 ESR => might work OK, but they are inferior to the MCZs (lower ripple, higher ESR => badder).

 

 

On Precision 470 cooling: Do these Northbridge caps benefit from the flow inside the green ducts? Or do they remain outside the ducts?

 

From these pics it looks like they are in a dead zone right between the ducts:

 

1370842218_518522534_2-Dell-Precision-47

2011-10-10121015.jpg

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NoelC    1,371

The taller 2200 uF one is definitely between the ducts.  I will have to check carefully whether the 1500s are in or out.  Perhaps I can work up some kind of mod that will improve airflow there.  This is not going to be a mission critical system, but will be used for training so it will be nice if I can restore it to its prior reliability (it used to run Vista x64 for months between update initiated reboots).

 

I can get Rubycon ZL 1500s.  Not being a wizard with spec sheets yet, and not seeing a ZL spec sheet at the same site you referenced, I'm not sure where to look.  Is the ZL a lower spec model?

 

Thanks, by the way, for all the attention and time you're spending on this.

 

One more question:  Given that I'm going to pay a bit more attention to the cooling, should I replace the Rubycon caps that have not obviously failed?

 

-Noel

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TELVM    172

The Ruby ZL are inferior to the Panny FJ for this application  :no:  .

 

I'd try to get Nichicon HN or, even better, Nichicon HZ.

 

While we're at it I'd replace all the lytic caps on that mobo, or at least the most mission critical ones (CPUs VRMs, Northbridge VRMs, RAM VRMs). If the comp is ~2005 vintage they must be tired after a decade.

 

It's my pleasure, I like tinkering with comps  :yes:  .

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MrMaguire    17

I agree completely. All of those capacitors have been constantly subjected to the same stress and heat since 2005. My bet would be that the ones that haven't failed already, will fail soon after you get it working again.

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