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Old 03-04-2019, 11:23 PM   #41
DesperateDude
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Smile Re: Axle typhoon ax-p400l (400W) PSU Dead

Yeeehaaa!! Guys Great news!!

R15 is indeed a 4.7ohms resistor I double checked and it had gold as the 3rd ring.

Anyway I've removed the 1ohm resistor and the resistance became between VCC and ground to around 395ohms and for the other side I see the small capacitor being charged and then meter stops.

Anyway back to the topic. I tried to turn on the PSU without that 1ohm resistor, guess what IT WORKED!!

Measured 5v standby and it was there and DM311 was getting around 15v to its VCC pin.
Also then I've shorted green and black then measured the rest 5v,3.3v and 12v and all were there.

THANK YOU VERY MUCH GUYS Specially momaka

But still now over. I have few more things to ask from you guys.
  1. When I power on the PSU I can hear a very low noise it's just like the noise when a big capacitor charges but it doesn't stop it is constant.
  2. When I shorted green and black I get a noticeable hissing sound. So I immediately removed the shorting on black and green not to damage anything.
  3. After all these I just tried touching the backside of the circuit and under the 3.3v transformer and near the transistors (The ones I tested yesterday) and diodes, it was too hot and I was afraid if I used this any longer something would blow up.

Also, I just checked some removed parts when I was doing the early repairs, There is a 100K ohms resistor which I don't remember where it was. Could this come in the place where 1ohms one was? Because I don't feel good to keep a circuit with empty part slots

Once these small issues are fixed I can have a working PSU again

Anyway Thank you very much all of you again for your valuable time,effort and helps. I was in the brink of throwing this away if it wasn't for you guys
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Old 03-06-2019, 09:20 PM   #42
momaka
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Default Re: Axle typhoon ax-p400l (400W) PSU Dead

There you go! Glad to help.

Quote:
Originally Posted by DesperateDude View Post
When I power on the PSU I can hear a very low noise it's just like the noise when a big capacitor charges but it doesn't stop it is constant.
Could you be more specific what that noise is? Is it like static electricity building up and/or discharging? Or what exactly?

Quote:
Originally Posted by DesperateDude View Post
When I shorted green and black I get a noticeable hissing sound. So I immediately removed the shorting on black and green not to damage anything.
Sometimes the PSU can whine and make strange noises at low load. Try putting one 20-40W 12V car/halogen bulb on the 5V rail and another 20W one the 12V rail... and maybe several 10-30 Ohm 1-W resistors on the 3.3V rail. This should keep the PSU comfortably loaded.

Quote:
Originally Posted by DesperateDude View Post
After all these I just tried touching the backside of the circuit and under the 3.3v transformer and near the transistors (The ones I tested yesterday) and diodes, it was too hot and I was afraid if I used this any longer something would blow up.[/B]
Do you mean the 3.3V toroid coil? As shown here:
https://www.badcaps.net/forum/attach...7&d=1550326104
Also which "transistors"? On primary? Or do you mean the rectifying diodes on the heatsink on the secondary?

Quote:
Originally Posted by DesperateDude View Post
Also, I just checked some removed parts when I was doing the early repairs, There is a 100K ohms resistor which I don't remember where it was. Could this come in the place where 1ohms one was? Because I don't feel good to keep a circuit with empty part slots
Yes, possibly.
How big is that resistor, though? (As in, power rating) - 1/2 Watt? 1/4 Watt?? Less/more? Smooth finish or gray with "rough" finish? The latter could indicate a snubber resistor. On that note, what's the value of R14?

Also. I noticed a few more things possibly wrong.
You say diode D6 is FR104 and diode D7 is FR107. What about the diode connected to R14 and C8? (I think that's diode D5???? ) If anything, that diode that connects to R14 and C8 (that I drew in BLUE on the corrected diagram) should also be an FR107 or similar diode. Reason being is that it's part of the 5VSB snubber circuit, and so it is typically a high-voltage part - usually rated for 600V minimum (and not uncommon at all to see 1000V diode use there.) Meanwhile, D6 and D7 don't necessarily need to be high-voltage parts like that. So the FR104 diode should be okay in place of D6 and D7 positions, I think.

To proceed more gradually with the repair, before doing any testing on the main PS (3.3V/5V/12V voltage), first try testing the 5VSB extensively. Connect some kind of a load on the 5VSB circuit so that it draws around 1 Amps of current. Let the 5VSB sit like that for 20 minutes. If nothing burns out, consider the 5VSB fixed. While doing this test, though, please also measure the Vcc voltage going to the DM311 IC. According to the DM311 datasheet, Vcc voltage should not exceed 20V. If it does, disconnect power/load from 5VSB immediately. Any voltage over 20V is what could be killing tbe DM311 chip in this circuit. So we will need to take care of that.

Last edited by momaka; 03-06-2019 at 09:24 PM..
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Old 03-06-2019, 10:38 PM   #43
DesperateDude
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Smile Re: Axle typhoon ax-p400l (400W) PSU Dead

Quote:
Originally Posted by momaka View Post
Could you be more specific what that noise is? Is it like static electricity building up and/or discharging? Or what exactly?
I am not sure how to tell it. I will try to record these sounds if possible. Just for now think it as a little "queek" sound.

Quote:
Originally Posted by momaka View Post
Do you mean the 3.3V toroid coil? As shown here:
https://www.badcaps.net/forum/attach...7&d=1550326104
Also which "transistors"? On primary? Or do you mean the rectifying diodes on the heatsink on the secondary?
No not there, Under these components (Around these black little coils) which are in the secondary side of the small transformer (3.3v)
https://www.badcaps.net/forum/attach...3&d=1551519416
I think in this picture you can see the two transistors before the coils. Under them which gets hot.

Quote:
Originally Posted by momaka View Post
How big is that resistor, though? (As in, power rating) - 1/2 Watt? 1/4 Watt?? Less/more? Smooth finish or gray with "rough" finish? The latter could indicate a snubber resistor. On that note, what's the value of R14?
Just a 1/4 watt small resistor. Like the image I attached.

Quote:
Originally Posted by momaka View Post
To proceed more gradually with the repair, before doing any testing on the main PS (3.3V/5V/12V voltage), first try testing the 5VSB extensively. Connect some kind of a load on the 5VSB circuit....
Right now DM311 gets around 15v. I'll try under load let you know.

By the way, I will post the other findings soon. Like the diode and etc...

Thank you very much. I wouldn't be able to fix this without you
Attached Images
File Type: jpg resistor-100k-ohm-14w-5.jpg (16.6 KB, 6 views)
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