Fun with fixing I-Micro power supplies

[joshnz]

Re: Fun with fixing I-Micro power supplies

Very nice thanks for sharing.

[momaka]

Re: Fun with fixing I-Micro power supplies

I am simply NOT convinced that you will ever get 400 watts out of that smaller transformer.......whereas that so called "terrible" Bestec WILL hold 250 watts.

Even 250W would be pushing it for that small transformer of the I-Micro, especially considering the fact that it is running at a lowly 34 KHz. It is labeled as a "ERL35" transformer, but it is definitely not, I can tell you that. Looks like "33" or possibly even "28" size. Meanwhile, the Bestec's proper "35" transformer should be good for up to 300-350W sustained.

So yeah, you can tell if a PSU is crap straight away by its main transformer. If it's "33" and H-bridge, forget about doing anything more than 250W continuous... if even that, because if the output caps are not up to the job (and they likely won't be), then prepare for ripple waves on the output larger than a tsunami .

[Dan81]

Re: Fun with fixing I-Micro power supplies

Looks like "33" or possibly even "28" size.

It's a real 33 size. I have a Intex 28-er and the 28 is even smaller than what those iMicros use.

BTW,I just had an PSU exact to that iMicro blow its fuse after I installed PI coils and completed the AC filtering that now awaits fixing,along with the Intex 28-er that is an candidate for some lil' modding.

The cause for blowing isn't exact,but I think it's because I tried securing the AC filtering choke with super glue,which if I'm not mistaken it's conductive,and from that fuse the was heard. It's literally CRACKED. I also discarded my Deer PSU - by now my rule is it's not worth anything UNLESS it's an Allied. (Allied PSUs are the more "beefier" versions of L&C/Deer PSUs)


Until I fix it I installed my old Key Mouse built Rexpower PX-400 into my system. Blows quite warm air after an certain time but I don't think it's gonna blow - maybe it's powering an A64 AM2 CPU but most of this PC is low power (1TB HDD,GT210[8400GS],1.50GB DDR2 and as I said a Athlon 64 3200+ single core) At least it has an bridge rectifier - strange thing,all SG6105 based PSUs I've had,they all had an bridge rectifier - even my Linkworld-built Powerlink PSU!

[kaboom]

Re: Fun with fixing I-Micro power supplies

completed the AC filtering

ASSuming it's not any of the semis...

Maybe you put the common mode choke in 90 degrees out, putting one coil across the line and the other across the input to the supply.

The ones with the base can be off and still put in- dead short.



Depending on your PCB, L and N will be reversed; just be sure to put one coil in series with each current carrying conductor.


That fuse cracked because you inadvertantly made a bolted fault.

[Dan81]

Re: Fun with fixing I-Micro power supplies

ASSuming it's not any of the semis...

Maybe you put the common mode choke in 90 degrees out, putting one coil across the line and the other across the input to the supply.

I used a wire choke and installed horizontally (parallel with board) on the desired place on the board (my PSU was the same as the last iMicro everell fixed. However,mine came with a bridge rectifier from factory)

BTW,the only parts missing were 2 PI coils,a common mode choke (which courtesy of my stupidity made it blow because I should have installed it vertically [parallel with the primaries and bridge rectifier ) and a X cap (yellow and rectangular caps IIRC). Maybe installing the choke vertically and replacing the fuse will fix it? What do you think?

[ben7]

Re: Fun with fixing I-Micro power supplies

ASSuming it's not any of the semis...

Maybe you put the common mode choke in 90 degrees out, putting one coil across the line and the other across the input to the supply.

The ones with the base can be off and still put in- dead short.



Depending on your PCB, L and N will be reversed; just be sure to put one coil in series with each current carrying conductor.


That fuse cracked because you inadvertantly made a bolted fault.

Yes I second that, only a very severe short circuit (low resistance) would make a fuse do that, UNLESS, it was just a cheap fuse with a low interrupt rating xD

Make sure you have installed the EMI choke the right way, and be sure to double check things like the bridge rectifier and switching transistors for shorts, just in case
Oh, and make sure the EMI filter choke hasn't gone open-circuit now too!

FYI, it would be best to use a "dim-bulb tester" for this. You just use an incandescent lightbulb in series with the PSU to limit the current. If there is a short circuit, the bulb will glow brightly, but it is much less likely for components to be damaged.

[Dan81]

Re: Fun with fixing I-Micro power supplies

Oh, and make sure the EMI filter choke hasn't gone open-circuit now too!

I don't think that's really possible since it's just 2 wires wrapped around a ferrite bead.

[ben7]

Re: Fun with fixing I-Micro power supplies

I don't think that's really possible since it's just 2 wires wrapped around a ferrite bead.

Fault currents CAN be hundreds or even thousands of amps ... they WILL blow out PCB tracks as well, fairly often. :P

[kaboom]

Re: Fun with fixing I-Micro power supplies

Fault currents CAN be hundreds or even thousands of amps ... they WILL blow out PCB tracks as well, fairly often. :P

If you're right across the transformer...

Not much will blow PCB traces, what sort of "ampacity" do they have?

It also depends on how "antiquated" or cheapened the wiring is. Like #14 for a loop length of 100 feet, y'know, cause "it's good for 15 amps." Or if things were backstabbed or not.

Those long, all-#14 ckts aren't likely to deliver more than ~200A fault current. I measured one with a 12.5A heater. Voltage dropped from 122 to 114 = 0.64 ohms. 122/0.64= ~190A bolted.

Then there's I2S- those little filter chokes, with their small wire, often survive, at least for one "accident." Microwaves often use small wire on the "monitor" or "short switch;" all this has to do is carry the load til the fuse blows. These are often on much better circuits (SABC) and the fault current is from 300-600A- the magnitude is higher, but that fuse is gone in just a few cycles.

Hence the high-interrupting ceramic fuse specified for MWOs.

[ben7]

Re: Fun with fixing I-Micro power supplies

If you're right across the transformer...

Not much will blow PCB traces, what sort of "ampacity" do they have?

It also depends on how "antiquated" or cheapened the wiring is. Like #14 for a loop length of 100 feet, y'know, cause "it's good for 15 amps." Or if things were backstabbed or not.

Those long, all-#14 ckts aren't likely to deliver more than ~200A fault current. I measured one with a 12.5A heater. Voltage dropped from 122 to 114 = 0.64 ohms. 122/0.64= ~190A bolted.

Then there's I2S- those little filter chokes, with their small wire, often survive, at least for one "accident." Microwaves often use small wire on the "monitor" or "short switch;" all this has to do is carry the load til the fuse blows. These are often on much better circuits (SABC) and the fault current is from 300-600A- the magnitude is higher, but that fuse is gone in just a few cycles.

Hence the high-interrupting ceramic fuse specified for MWOs.

Dan is from Romania, where they use 240V ... not 120V :P

[Dan81]

Re: Fun with fixing I-Micro power supplies

Fault currents CAN be hundreds or even thousands of amps ... they WILL blow out PCB tracks as well, fairly often. :P

Don't worry about the ferrite anymore since just the fuse blew,not a biggie for me. Replaced it,placed the choke in the correct position and now it works fine.

[ben7]

Re: Fun with fixing I-Micro power supplies

Don't worry about the ferrite anymore since just the fuse blew,not a biggie for me. Replaced it,placed the choke in the correct position and now it works fine.

haha ok xD

Good to hear that you got it working. :P

[Dan81]

Re: Fun with fixing I-Micro power supplies

haha ok xD

Good to hear that you got it working. :P

Yeah. After fixing it,I was reluctant to turn it on first because I thought it would go but it was okay at that point. I got a fuse from another iMicro board I discarded,and the wire choke and PI coils came from a Deer (it's a choke,nothing can harm from a Deer,and shock,that Deer had PI coils)

iMicro seems to be around here rebranded as Delux,but not that often - Delux uses either Sun Pro or iMicros for their 400W models,and easy to spot also:

iMicro/YX-GP built 400/450W Delux units have a rocker switch on the back.
Sun Pro 400W Delux units don't.

BTW,I've noticed Sun Pro built 400W Delux units are better than Raidmax - this makes me think Raidmax is worse than anything. I've seen Sumvision and Delux units being way better than Raidmax units,with the AT2005B (not 2005 from DEER) being one of the good platforms of Sun Pro. At least that one had PI coils unlike Raidmax.

Fun fact: When I tried to remove the cracked fuse,it broke in half!

[everell]

Re: Fun with fixing I-Micro power supplies

..... at that point. I got a fuse from another iMicro board I discarded.....

WHAT??? You didn't fix the I-Micro??? That was the fun part of this entire thread!

[Dan81]

Re: Fun with fixing I-Micro power supplies

WHAT??? You didn't fix the I-Micro??? That was the fun part of this entire thread!

I didn't fix the 400W one I had in my parts pile. It wasn't worth it with the wimpy heatsinks it had. The 450W rated one has better heatsinks,so it was worth fixing.

[everell]

Re: Fun with fixing I-Micro power supplies

I didn't fix the 400W one I had in my parts pile. It wasn't worth it with the wimpy heatsinks it had. The 450W rated one has better heatsinks,so it was worth fixing.

So did you fix the 450W IMicro and get it working?

I was just given a Okia-500ATX rated for 500 watts. And I thought the IMicro power supplies were bad. This Okia has a smaller than usual case size, is light weight, and has wimpy parts throughout. Four small diodes feeding a pair of Ricon 330 uF/200 volt main capacitors. Also the fan is stuck on this one. And this power supply is going to handle 500 watts????

[Dan81]

Re: Fun with fixing I-Micro power supplies

So did you fix the 450W IMicro and get it working?

I was just given a Okia-500ATX rated for 500 watts. And I thought the IMicro power supplies were bad. This Okia has a smaller than usual case size, is light weight, and has wimpy parts throughout. Four small diodes feeding a pair of Ricon 330 uF/200 volt main capacitors. Also the fan is stuck on this one. And this power supply is going to handle 500 watts????

Yes,I did get it to work. Now it's complete with PI coils,X cap and common mode choke. Also,replaced the old fan it had with a Titan fan (Delta built).

[everell]

Re: Fun with fixing I-Micro power supplies

Give us a picture of it so we can compare it with the first two I fixed in this thread. Together we can show the world what can be done with an IMicro power supply, even if it is a !@#$%^&*

[ben7]

Re: Fun with fixing I-Micro power supplies

Give us a picture of it so we can compare it with the first two I fixed in this thread. Together we can show the world what can be done with an IMicro power supply, even if it is a !@#$%^&*

Oh 'deer' xD

[Dan81]

Re: Fun with fixing I-Micro power supplies

Give us a picture of it so we can compare it with the first two I fixed in this thread. Together we can show the world what can be done with an IMicro power supply, even if it is a !@#$%^&*

I'll try doing so. Keep in mind that I don't have any dead FSP,Antecs or such to take parts from,so it may look quite bad.