What could cause this PSU to output 12.5V on the 12V?

[c_hegge]

Re: What could cause this PSU to output 12.5V on the 12V?

That's odd. The Jilin Sino datasheet (their real manufacturer, going by the logo in post 51) says 12A for the D304X

[Wester547]

Re: What could cause this PSU to output 12.5V on the 12V?

^ Whoops, my bad... I noticed the datasheet says 3DD304X, though, whereas the one I URLed just says D304X.... sort of confusing to see conflicting data but you're right since it's the manufacture of the switchers in the PSU in question.

[Pentium4]

Re: What could cause this PSU to output 12.5V on the 12V?

105 = 1 uF. The 1.0 signifies it's a 1uF as well. So they are the same. K means 10% tolerance.


As Th3_uN1Qu3 mentioned, the snubber is a large resistor and a ceramic (or sometimes polypropylene) cap in series with that resistor. From the picture you provided above, that would be large 47 Ohm resistor and that ceramic cap behind it (C4). Check me on that, though. They should be in series and together connected across the primary side of the main transformer.

May also want to transplant the snubber diodes that are across the BJTs from the donor PSU if they are of a bigger current rating and have at least the same or higher voltage rating.

Awesome thank you for the info, I thought that was the bleed resistor, stupid me the snubber diodes would be on the other side of the heatsink?

No, unless the 13009s are TO-3P or TO-247 while the D304Xs are TO-220. Both of them are rated for 12A, so assuming they are the same size, neither will handle more than the other.

They are BJT ST 13009's, I got a few of them off of Digikey. Like mentioned I should probably just upgrade the secondary silicon and transformer. Excited to try the new transformer tomorrow!

[c_hegge]

Re: What could cause this PSU to output 12.5V on the 12V?

Yeah, they are all BJTs. I meant their physical size. I can see from post 51 that the 304Xs are TO-220 size (the smaller size). Are the 13009s the same size (TO-220)? or are they physically bigger (TO-247/TO-3P)

[Pentium4]

Re: What could cause this PSU to output 12.5V on the 12V?

Yeah, they are all BJTs. I meant their physical size. I can see from post 51 that the 304Xs are TO-220 size (the smaller size). Are the 13009s the same size (TO-220)? or are they physically bigger (TO-247/TO-3P)

Oh gotcha, they're the same size

[c_hegge]

Re: What could cause this PSU to output 12.5V on the 12V?

^
I wouldn't worry about replacing them, then.

[Pentium4]

Re: What could cause this PSU to output 12.5V on the 12V?

Finally got some time for this, before I plug it in with the new transformer what are the chances it could explode into a fiery wake?

[momaka]

Re: What could cause this PSU to output 12.5V on the 12V?

If it's not the right transformer - high.

Put a light 60W bulb in series with the live AC line going to the PSU. If anything is wrong, you'll get fully lit bulb and no explosions. If you do that, though, don't put more than a fan or two for a load on the PSU because the bulb will start dropping too much voltage for the PSU to keep up.

[Pentium4]

Re: What could cause this PSU to output 12.5V on the 12V?

It wouldn't just pop the fuse? That's cool, how would I do that? I've never done that before

[momaka]

Re: What could cause this PSU to output 12.5V on the 12V?

Get a 40W to 100W incandescent light bulb and some wire. See attached diagram for wiring (all MS Paint style ).
NOTE: BE EXTREMELY CAREFUL AROUND THE BULB WHEN IT'S PLUGGED IN!

It wouldn't just pop the fuse?

No, because the light bulb is in series with the PSU. So if any component in the PSU tries to pull too much current due to a fault, the impedance of the PSU will become much lower relative to the bulb's impedance. This will make the light bulb glow. It pretty much works like a simple series resistor voltage divider.

[Pentium4]

Re: What could cause this PSU to output 12.5V on the 12V?

Wow thank you for the awesome diagram!! can I use any old wire? And I meant if it didn't like the transformer the fuse wouldn't just blow?

[momaka]

Re: What could cause this PSU to output 12.5V on the 12V?

Nope, fuse won't blow. With a 40 to 100W bulb, the bulb will pull about 0.33 to 0.83A of current. The fuse is rated much higher than that so it will never blow. However, the overloaded components could still overheat and die, so if the light bulb becomes fully lit and stays lit for more than a few seconds, unplug the PSU immediately.

[Pentium4]

Re: What could cause this PSU to output 12.5V on the 12V?

Okay, thank you for the info

[mariushm]

Re: What could cause this PSU to output 12.5V on the 12V?

Also use some decent wire, not network cable or IDE wires... something at least the size of the 12v cables in the power supply.
If you don't have a socket to put the lightbulb in, use a lot of electrician's tape to insulate any metal you could touch.

Smartest thing would probably be to put the lightbulb in a ceramic mug or something similar.

[999999999]

Re: What could cause this PSU to output 12.5V on the 12V?

Or just build it safer using a standard electrical box, pigtailed bulb socket, grounded AC socket, extension cord with a strain relief where it enters the box, and solid core 14 ga. wire with wire nuts as needed.

Electrical taping AC mains wires to a light bulb seems a little sketchy.

[mariushm]

Re: What could cause this PSU to output 12.5V on the 12V?

That's not what I meant. I meant solder the wires onto the bulb, then insulate everything using tape.
But I agree using sockets and taking safety measures is a very good thing.

[budm]

Re: What could cause this PSU to output 12.5V on the 12V?

You make a little box for it like this if you plan to work on alot of electronics.
http://s807.photobucket.com/user/bud...82195675176907

[mariushm]

Re: What could cause this PSU to output 12.5V on the 12V?

Here's what I bought a couple of months ago, but i never got around to build a box for.







It's a socket that converts the regular house bulb to the upper diameter socket (which are usually for 250-400w bulbs).. but the basic idea is that the top is plastic so no (or minimal risk of electric shock) and I can screw the wires to the socket.

Just have to make a box and cut a circle on the top to put the plastic circle through and add a double switch to the panel to turn off the power and it's done.

[Pentium4]

Re: What could cause this PSU to output 12.5V on the 12V?

Thanks for all the knowledge on how to do this safely, I will try this when I get some more free time at work

[eccerr0r]

Re: What could cause this PSU to output 12.5V on the 12V?

Just as a word of warning and maybe for the comical effect:

Don't use a CFL or LED light bulb for doing this

There's another thing these black body radiators are good at