Fixing Antec 400W Atx power supply
A friend of mine asked me take a look at his power supply, because suddenly it stopped working. Of course I said yes, and the first thing to check after I removed it’s top, was the fuse. The fuse was wrapped inside heat shrinking tube which made the checking a bit difficult. After peeling some of the shrinking tube I was able to measure it’s continuity and find out that it was blown. At that time I hoped this was the only problem, I replaced it and powered the supply, but my joy was short, because the new fuse was blown too.
Obviously the problem needed further investigation, so I went along and checked the rectifier bridge, which was ok. The capacitors looked ok, so the next thing I had to check was the two switching transistors. To do that I had to remove the hole radiator which contained more than the transistors. Checking the transistors gave me the answer to the problem, because I found both to be broken. But now a new problem was raised when trying to find replacements for the two transistors 2SC3320. I was only able to find these in stores across US and China and both of these places would make the shipping and tax costs to high to be worth buying from there.
Now I have only two options, one is for someone to have a broken power source that has these same transistors, and that they’re still working, and the other is to find a replacement for these transistors, which I tried but with no luck. I wasn’t able to find another transistor to match it’s characteristics.
This is the datasheet of the 2SC3320 transistor. If you have any ideas on how I could solve this, please comment.











April 24th, 2009 at 4:39 pm
What country are you in and what retailers do you usually use? I’m sure we could find something compatible.
April 24th, 2009 at 4:53 pm
Hi Bryce, I’m in Romania and I usually order parts from http://www.tme.eu.
A friend told me that if I replace them with transistors that have some of the characteristics just slightly different the power source will break again in short time because the whole switching circuit was tuned in for those specific transistors.
April 25th, 2009 at 4:00 pm
I’ve fixed several of those power supplies already with great success! The characteristics do NOT have to be EXACT – I think your friend doesn’t know his switching power supply circuits very well. I used common (off the shelf) NTE2311 transistors (with plenty of heat sink compound) and they work great! When using substitute transistors, ALWAYS meet or exceed the Voltage and Current handling capability FIRST. Speed may be a concern, but not usually. The bias is often easy enough to modify (Wow – Change a resistor, or add a diode). Hope that helps you!
April 25th, 2009 at 8:38 pm
Hi Fred, NTE2311 seem really close to the original transistors, but unfortunately I cant find those either..
Where are you from ?
April 27th, 2009 at 4:12 pm
i’ve seen a lot of switching power supply that uses FETs as switching transistors why not modify that power supply a bit to make it work with FETs and you can get FREE sample FETs from On semiconductor
and i also checked the pricelist of a local vendor here in Philippines and i was surprised that 2SC3320 just costs 35 pesos or almost 72 cents in dollars
April 27th, 2009 at 4:22 pm
hmm, that sounds interesting. Could you please check the price for shipping to Romania a small package at your local post office. If the price is reasonable maybe we can arrange for you to send me a couple of those transistors.
thanks
April 28th, 2009 at 4:40 pm
i asked a friend who ships parts from Philippines to Europe and he told me that a registered mail to Europe just cost around 2-4$USD
2-3weeks and the local vendor that sells 2SC3320 is not that near to my place so i have to pay a little shipping charge which is 3$ next day delivery all in all it only costs 5-7$USD to ship the parts to you
April 28th, 2009 at 10:30 pm
Thanks for checking, it sounds ok, I’ll get back to you with details by email.
June 8th, 2009 at 4:58 am
Solved or not?
June 8th, 2009 at 10:35 am
not solved, Joseph was unable to find the transistors in stock at he’s supplier so now I’m still searching