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High Power ATX-410-212 by Sirtec Repaired
Yesterday I fixed a P.F.C. Power Supply that had taken quite a while before I found the cause. And today another Power Supply finally got fixed by yours truly that I previously already had examined. And in which I had replaced a bad 1000 uF 16V Capacitor. This was a quite well known model HIGH POWER ATX-410-212 by Sirtec (see next photo).
This ATX410-212 PSU is controlled by a big SG6105DZ chip. And I probably already had checked all Mosfets and/or Transistors on the Cooling Plates. (Which I always simply desolder completely with the entire Alu Plate out of the board without removing the Semiconductors on them). None of the Semiconductors were bad. Because I could not find the cause I also had replaced the SG6105 controller. The Supply still did not start. So I had put it aside to check it on another time.
Today I felt lucky, that is why I inspected the mentioned ATX Power Board again. And to my surprise I noticed something I hadn’t seen before. Because of the sunny day, it was likely been unnoticed on a previous dark Winter’s day. It was a dark spot under a small Diode with Boardmarking D503. I measured the resistance with my Digital Meter and it was completely shorted. Sadly I could not see any text on the diode after I had removed it from the Supply Board. It was completely blank.
But before I would replace it by another Diode I checked the voltage over the now removed D503 if there was any. It was switched parallel to a 470uF 16V Capacitor (C407) with its plus pole to the cathode of D503, and with its min pole to the anode of D503.
And as I already suspected it indeed was the failure that kept the ATX from working. Over the C407/D503 there was a voltage of about 5V and the Supply worked nicely again. Although still
without the D503 inserted, I used a Light Bulb to prevent any unexpected Burnouts or short circuits from happening. I couldn’t find any schematic or information on the D503 diode. So I replaced it by a 5V1 Zener. And even if the zener voltage afterwards checks out to be chosen higher, replacing it by a for instance 6.2Volt later is always easily possible. A again short circuiting D503 would be proof of that. But changing it right now to a higher voltage than 5.1 Volt could be dangerous.
On above Photo the burned out D503 Diode is shown. The C407 470uF 16V Capacitor is right next to it. The black spot in the Board is from the burning of D503. Also notice the Purple Wire from the ATX Power Connector (is 5V standby) that is connected to both the plus pole of C407 and the cathode of D503.
On next Photo the Board without D503 is shown more closely. Also notice the text on the left: 360W 410W T8A/250V that mentions the value of the used Fuse. And on next Photos the working ATX Supply is shown still without the D503 in place. But first with a Light Bulb in between one of the 230V AC input wires as a protective measurement.
But nothing nasty happened, and the Supply worked like new again!
Other text that could be seen on the Board was for example: Sirtec No 526-2, and
Wannien 101VO Rev A2, and a date: 2004-08-06.
Again I must conclude that also fixing this SMPS unit did not cost any money at all! Just a small zener that won’t be any problem for any Repair Engineer.
On following photo the arrow is pointing to SG6105DZ and the Wires Purple (5V Standby) and Green (Power on) are shown. Below on the left the C407 Capacitor. The white 2 pole connector on the right is for the Fan. Note: The 5V standby always supplies +5V, even when all other Power Lines are not active!
Next photo shows the back of the board with in top-middle the holes from the removed D503.
Last taken photos clearly show that the 410Watt ATX, with SG6105DZ , supply is operating fine again. Even the silently rotating fan is working like new with its four (3V) Blue Leds.
Another great Power Supply Repaired and Ready to be used again !
Albert van Bemmelen, Weert, The Netherlands.
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Note: You can read his previous repair article in the below link: