BlueCase DT500 KN1009P31154 Hissing and shutting down

[rogfanther]

Hello,

Another one in the realm of the not-so-true real watts. I asked an importer if for "nominal power" he meant that the number appeared in the name of the psu.

Well, this came with a bunch of others to try fixing.

It hisses a lot, without load. 5VSB is ok, also the other voltages when jumpered on. No caps bulged ( those in the picture are the original ones ) .

When jumpered on with load ( just one hard disk ) it shuts down and won´t start. Tried changing the rectifiers, same thing.

Tried changing the caps one at a time, to try in identifying the culprit, also no go. Even after changing all of them, it still hisses and shutdown.

With the paper tube trick, it seems the sound comes from the big transformer.

As I´m already out of good caps to use, ( need to decide which brand/series/values to buy even from Badcaps or from other places ) and cannot spend too much money in this psu, I need to decide what to do.

What more could be causing this, other than the transformer ? The supervisor chip is a HS8109.

The original caps are all from that brand with a big "C" inside a "S".

Thanks.

[selldoor]

Hi - have you now replaced ALL the caps Including the BIG Yalecon ones
I doubt if they are good caps.

Are these the Caps you refer to
http://capacitor.web.fc2.com/image2/cs01.jpg

What brand/series did you use for replacements

Picture of the bottom of the board might help - have you tried resoldering the transformer connections

EDIT - did the green cap bottom left leak onto the board - did you clean it up properly.

[rogfanther]

No, not replaced the yalecon ones. I only have those cheap 330uF ones from gutless wonders.

I used a bunch of Nichicon PM and HE, also Panasonic FM that I had lying around.

Here are the pictures of the bottom.

No cap leaked, the smudges are remains from glue that was between the caps and the toroid.

Will try resoldering the big transformer.

Edit : transformer resoldered, same thing. Hiss without load, won´t start ( but stops hissing ) with load.

[Th3_uN1Qu3]

Hissing means oscillation, irregular operation of the control circuit. Sounds like something is gone in the driver circuit since it stops under load. Check the driver transistors (they will be somewhere near the base drive transformer, in the secondary side, usually C945 in TO-92, but depending on the controller and its supply voltage they might be 1A ones, in a fatter package) and the drive circuit in the primary, on the other side of that transformer. Here you have a schematic, values may not be exact but the basic circuit will be the same.

http://www.smpspowersupply.com/ATX_p..._schematic.pdf

By the sound of it, i'm fairly certain that one of the driver transistors is gone, everything else is probably okay. Replace both of them and give it a try.

[rogfanther]

They are D1616A. Replaced them with BD139, that was the most similar we could find in the store. Will need to check in the junk pile at home if I found the exact same part.

But the behaviour remains the same. Voltages ok without load, shutdowns with load.
I also measured the diodes around the transistors ( Q1 and Q2 in your drawing ) , but all of them measure ok. The cap in a position C8 is a 10uF x 50V, also measures ok (10.5uf ) .

[Th3_uN1Qu3]

Not sure BD139 is good for switching, i've only seen them in audio. Try a closer replacement. Once you're sure those are okay but still no go, check D8/D9 (most likely those will be 1N4148) and C9/C10.

[everell]

Originally Posted by Th3_uN1Qu3

Hissing means oscillation, irregular operation of the control circuit. Sounds like something is gone in the driver circuit since it stops under load. Check the driver transistors (they will be somewhere near the base drive transformer, in the secondary side, usually C945 in TO-92, but depending on the controller and its supply voltage they might be 1A ones, in a fatter package) and the drive circuit in the primary, on the other side of that transformer. Here you have a schematic, values may not be exact but the basic circuit will be the same.

http://www.smpspowersupply.com/ATX_p..._schematic.pdf

By the sound of it, i'm fairly certain that one of the driver transistors is gone, everything else is probably okay. Replace both of them and give it a try.

The schematic is very interesting. The PWM IC is not labeled, but the pinout matches the "chip of the year" 2008. Perhaps this schematic is for a "economy" Solytec psu?

[Th3_uN1Qu3]

It is labeled on the right. It's a SG6105.

[rogfanther]

Hi,

Still searching for suitable replacements for those transistors, and waiting for some caps to arrive in the mail. While I don´t see why, could it also be the primary caps that cause this fail ?