[rescue] Sun T5240 power supply failure?

John Hudak jjhudak at gmail.com
Mon Feb 29 15:24:29 CST 2016

Sparky eh?  Cool.......

Well you didnt say if the machine died or not after you saw the sparks.

Things can cause sparks that may not harm the PS or the boards.
These things include:
Build up of dust, moisture, 'critters' - Generally what happens is that a
bridge is formed between two voltage lines, e.g. the 120/220 vac lines
inside the PS, or 5VDC to GND.  Once a bridge is formed, it creates a short
circuit and the electrical energy will ionize the bridge (if it is weak
enough), clearing the bridge and the PS continues to function.  If the
bridge is large enough - e.g. capable of carrying the electrical current,
then the weakest link in the current path will overheat/vaporize causing
sparks (and in most cases, releasing the magic smoke..lol).  If this
happens, the PS needs to be repaired

Other things that can cause bridging (aka shorts) include failing
capacitors, resistors, transistors, diodes, etc.  If the failure mechanism
is a short, the inrush of current will cause them to vaporize, and
depending on the path, may  take out other components.  The reasons for the
failure include power surges, power cycling, and component degradation over
time that may cause increased current draw, resulting in the weakest link
in the path failing.

Of note, there was a well know capacitor failure problem in the 2006-2010
timeframe (IIR the dates correctly) where the mfg produced bad quality
capacitors that after about 2-4 years, depending on use, would burst.
Quite anazing to see.  Many PC MB along with Apple all in one MB were
affected by the bad  caps. The MB in one of my PCs had the electrolytic cap
explode, sending aluminum paper pieces all through the machine, and the
only thing left on the MB were the two leads soldered to the board...quite

One needs to do some troubleshooting of your PS to determine what has

One of the common activities done on older machine is to 're-cap' the
PS....e.g. replace all the electrolytic capacitors with new ones.

good luck

On Mon, Feb 29, 2016 at 3:21 PM, Steven M Jones <smj+rescue at crash.com>

> On 02/28/2016 23:13, chris t wrote:
> > One of the power supplies on my new T5240 just shot out a bunch of
> sparks,
> "New?"  New to you, but not new from the factory, or NOS? I think this
> model was introduced around 2009...
> Did you have contact with this machine during it's prior service life?
> PSUs are not immortal, and if you weren't working with it before, you
> don't know what (ab)use it may have seen.
> "Sometimes people just explode. Natural causes." -- Repo Man
> > Anyone else see this sort of thing happen?  I'm pretty spooked, to be
> > honest.
> I haven't had a PSU go sparky, but I've certainly had them fail. And as
> Peter mentioned, there are sometimes transient or permanent wiring
> issues cropping up.
> You might want to try:
>   * using a multimeter to check levels at the outlet(s)
>   * putting a UPS and/or line conditioner between T5240 and outlet
>   * using a Kill-o-watt or similar to monitor power draw from machine at
>     next power-up
> Hope that helps,
> --S.
> _______________________________________________
> rescue list - http://www.sunhelp.org/mailman/listinfo/rescue

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