My Dynex 350W lost it's mojo

[bigbeark]

Last night I fired up my Gigabyte box, uses an Inte li875 chipset. This machine has always had a speed up/slow down action on boot up.
It was booting but I was getting "video out of range" message when it went to load Linux Mint. This NEVER happens on Linux machines. So I started looking around and found that I must have dislodged the 12v auxiliary power
4-pin connector. This is a 20-pin ATX machine, by the way. When I turned on the rocker switch on the PSU, I heard a pop. After that the machine would start up, but not boot.

I swapped in another Dynex PSU and the machien booted right up with no racing from the PSU.

So I took the cover off the old PSU (which was really almost new). No heat damage of any kind, no domed caps, nothing. The fuse must be intact or the PSU wouldn't run(?).

What should I look for?

I hooked up my dubious Thermaltake power supply tester and it shows nothing is wrong!!

How do I use my multi-meter to test this PSU?

I will recap if the thing is not burned out totally, but want to ensure it's worthwhile.

I would appreciate your suggestions.

[shovenose]

Re: My Dynex 350W lost it's mojo

A pop suggests that one of the switchers could be bad

[c_hegge]

Re: My Dynex 350W lost it's mojo

Agreed. Check the primary switching transistors

[bigbeark]

Re: My Dynex 350W lost it's mojo

Agreed. Check the primary switching transistors

So according to http://en.wikipedia.org/wiki/File:AT...ransparent.png, these would be attached to the heatsink that is between the large primary caps and the transformers?

Can I test these with a multimeter? What is the proper testing method? Thanks, Barry

[seanc]

Re: My Dynex 350W lost it's mojo

Did you smell anything 'cooking'?

[bigbeark]

Re: My Dynex 350W lost it's mojo

Did you smell anything 'cooking'?

No smells or smoke at all. Just a "pop" when I turned the rocker switch to ON

[370forlife]

Re: My Dynex 350W lost it's mojo

I think what you might be hearing is the switch arcing a bit when you switch it on. Does the power supply still turn on?

[bigbeark]

Re: My Dynex 350W lost it's mojo

I think what you might be hearing is the switch arcing a bit when you switch it on. Does the power supply still turn on?

I think I found the problem. Looks like the red wire that attaches to what I think is a square "X" capacitor (next to the transformer) is not connected to one leg of that cap, but should be. The wire is loose, You can see its sort of pushed out of the PCB, I think the two wires should have been joined by a puddle of solder. There is a black scorch mark there. Tell me what you think.

[shovenose]

Re: My Dynex 350W lost it's mojo

definitely something happened there-probably the high-voltage caused an arc aross the bad connection, making a pop noise

[momaka]

Re: My Dynex 350W lost it's mojo

It's hard to tell from the pictures, but if the red wire is indeed loose or has become unsoldered, then that's definitely the problem. As shovenose suggested, the noise could have come from the bad connection.

[ratdude747]

Re: My Dynex 350W lost it's mojo

thats the voltage selection switch wire... that would explain it if you are on 120v (USA or canada)... if 240v, then nothing because turning the switch on would burn the unit out. switching it off on 120 drops the voltages... and ehnce why you have a problem.

resolder that wire. the scorch if from the AC arcing...

[Agent24]

Re: My Dynex 350W lost it's mojo

Looks like part of that pad\track has actually been ripped off. I'm guessing they built it badly, there was too much strain on it and it broke.

Might work just fine if you reconnect that wire

[bigbeark]

Re: My Dynex 350W lost it's mojo

The red wire was loose. Upon closer inspection, I realized that it was supposed to be attached to a common ground plate in that area. The solution was to attach it to another wire that was firmly attached to the ground plate. Seems to have done the trick as test board now posts. Was able to document all the caps while I was in there so I can in future do a recap. Other than the caps, which are a mixture of CapXcon and FCon, the Primary side is complete with no fudges, although the Primary caps are only 470uf 200V.