Antec 350 Recap Epic Fail

[bigbeark]

Re: Antec 350 Recap Epic Fail

Thanks everyone, really appreciate the help.

I repeated my testing of the bridge rectifier with a better ohm meter with better probes. I placed one probe on the solder spot where the heatsink was attached to the PCB and the other probe on each of the legs of the bridge rectifier in turn. This time every leg showed almost no resistance between the leg and the heatsink anchor point. Can I conclude that bridge rectifier KBU8J is internally shorted?

The fuse (beside the green disk) shows no continuity - it is blown. That rubber sleeve will be destroyed getting it off to see what the rating is. Thanks Ben7. I totally missed seeing it.

What appears to be carbon tracking is not. There is some sort of clear plastic lacquer which ends right above the duller black plastic of that coil.
I will indeed remove the big caps and clean that gunk off.

[delaware74b]

Re: Antec 350 Recap Epic Fail

I see carbon tracking around the small transformer in the lower left corner of your first photo, reattached and circled in yellow.

Also, removed -any- and -all- of that brown glue on that board. I had a power supply in an HP DC5100 small oven short out because of the glue.

Was there a plastic shield installed under the circuit board?

[ben7]

Re: Antec 350 Recap Epic Fail

This PSU uses an IC instead of a fuse. I used the Ohms setting on my multimeter, but did not detect a short to ground on the bridge rectifier.

I did see a slight deflection of the needle between the negative and positive legs but that
was not a repeatable reading. I assume the rectifier became charged and would discharge over time.

On the left side of the picture, there is a fuse, it is standing upright, in some plastic shrink-wrap tubing.

[bigbeark]

Re: Antec 350 Recap Epic Fail

Because the switch is off, that does NOT mean there is no voltage in the circuits. It likely was a N-GND short, or possibly they messed up big time and put the switch on the neutral, so the components are always live (on hot wire)

Is the fuse measuring good?

Check the bridge rectifier to see if it is shorted.

I would think the MOSFETs would be OK. (usually the heatsink is connected to the positive DC rail. but I may be wrong)

This PSU uses an IC instead of a fuse. I used the Ohms setting on my multimeter, but did not detect a short to ground on the bridge rectifier.

I did see a slight deflection of the needle between the negative and positive legs but that
was not a repeatable reading. I assume the rectifier became charged and would discharge over time.

[bigbeark]

Re: Antec 350 Recap Epic Fail

Imagine your finger conducting the primary heatsink and the case... Yeah that happened to me... It was an Antec Smartpower 450 and the switch was at the off position but it was connected to neutral..

Did you find the shorted part?

I have some other PSUs where a screw is threaded from the case into the Primary heatsink, obviously this is intended as a safety feature.

If the heatsink can "go live" why is the heatsink not directly grounded to he case, which of course is grounded to the power cord?

[c_hegge]

Re: Antec 350 Recap Epic Fail

^
I've done a similar thing, to a similar PSU (an Antec SL350) and was saved by a similar device.

[goodpsusearch]

Re: Antec 350 Recap Epic Fail

This saved me: http://www.conrad.com/Siemens-RCD-Fa...-int&pi=628032

[bigbeark]

Re: Antec 350 Recap Epic Fail

Imagine your finger conducting the primary heatsink and the case... Yeah that happened to me... It was an Antec Smartpower 450 and the switch was at the off position but it was connected to neutral..

Just after it happened, I said to myself, lucky I didn't touch that heatsink...

That must be frightening and painful at the same time. OUCH!

[goodpsusearch]

Re: Antec 350 Recap Epic Fail

Imagine your finger conducting the primary heatsink and the case... Yeah that happened to me... It was an Antec Smartpower 450 and the switch was at the off position but it was connected to neutral..

[ben7]

Re: Antec 350 Recap Epic Fail

This 350-watt Antec was non-working. Three fuyuhu caps in the secondary were vented, so I recapped this PSU, removing every blasted fuyuhu cap and replacing with quality caps.

I had securely reassembled the PSU, but the top was off, and as I attemped to push the power cord in (switch was off) there was a loud pop and some sparks. The primary side heatsink was apparently live and touched the case.

Visual inspection confirmed this, slight heatsink melt and blackened area on inside of steel case.

So I'm guessing one of the components on the primary heatsink was shorting directly to ground. However, I repeat, the rocker switch was in the OFF position.

What happened to cause this? I went over all the caps I replaced and everything was done properly. There is no burning on any components that I can see.

I have now removed the wires so I could remove the heatsink, but the wiring was untouched when the short happened.

How do I test the Mosfets for short to ground? There is no continuity between any of the pins on the big MOSFETS and no continuity to the heatsink except at the mounting screws The smaller one has continuity between pins 2 & 3, but none to the heatsink except at the mounting screw.

Because the switch is off, that does NOT mean there is no voltage in the circuits. It likely was a N-GND short, or possibly they messed up big time and put the switch on the neutral, so the components are always live (on hot wire)

Is the fuse measuring good?

Check the bridge rectifier to see if it is shorted.

I would think the MOSFETs would be OK. (usually the heatsink is connected to the positive DC rail. but I may be wrong)

[bigbeark]

This 350-watt Antec was non-working. Three fuyuhu caps in the secondary were vented, so I recapped this PSU, removing every blasted fuyuhu cap and replacing with quality caps.

I had securely reassembled the PSU, but the top was off, and as I attemped to push the power cord in (switch was off) there was a loud pop and some sparks. The primary side heatsink was apparently live and touched the case.

Visual inspection confirmed this, slight heatsink melt and blackened area on inside of steel case.

So I'm guessing one of the components on the primary heatsink was shorting directly to ground. However, I repeat, the rocker switch was in the OFF position.

What happened to cause this? I went over all the caps I replaced and everything was done properly. There is no burning on any components that I can see.

I have now removed the wires so I could remove the heatsink, but the wiring was untouched when the short happened.

How do I test the Mosfets for short to ground? There is no continuity between any of the pins on the big MOSFETS and no continuity to the heatsink except at the mounting screws The smaller one has continuity between pins 2 & 3, but none to the heatsink except at the mounting screw.