Fun with fixing I-Micro power supplies

[everell]

I decided to start another thread for a "cheap" power supply, the I-Micro series. A salesman at a computer shop asked me if I knew why The I-Micros had a problem of being dead out of the box. I had five "bad" ones and a pc board from one I had gutted some time ago. They varied from 350 watts, to 400 watts, to 450 watts. They also used three different power supply boards. Pictures of the circuit boards from three of them are in this post. All had capacitor outputs with no room for coils to form pi output filters. This was a key issue for me. I don't want to try improving a power supply with pc board not even having room for output filter coils. All but one board used main capacitors branded ZWCON. Measured capacity was only 60% of marked value on all of them. Output capacitors (bloated and otherwise) were branded HEN. Of the five pc boards, only one had a line input filter. For switching transistors they used 13007 or 4124 switching transistors. Two boards had larger switching transformers, four had smaller switching transformers. Size didn't seem to match wattage rating.

[everell]

Re: Fun with fixing I-Micro power supplies

The remaining two power supplies and "junked" pc board all had ATX 12V2 VER 2.0 marked on the pc board. This pc board has room for full pi filter on the output circuits. But all three boards had one output filter capacitor, the pi filter coil space was jumpered, and one capacitor space was not used. Even more curious, output filter capacitors for all three outputs was 680 uF/25 volts. I don't think that is enough filtering to meet ripple requirements for a 400 watt or 450 watt power supply!

Seems to me that I have seen this ATX 12V2 VER 2.0 pc board in other off brand power supplies. Has anyone else seen one?

[stj]

Re: Fun with fixing I-Micro power supplies

the word "shit" seems insuficient.

[everell]

Re: Fun with fixing I-Micro power supplies

The first "fixer-upper" is rated for 450 watts as shown in the picture. I used the best of the heat sinks I had from the five units. I removed the ZWCON main capacitors and replaced them with Fuhjyyu pullouts from a Antec Smart Power. At least their capacitance was in spec! I used the larger sized switching transformer, and a pair of pull-out D209L switching transistors. I installed three coils in the pi output filters, and used some pull-out capacitors to finish off the output filter circuits. I gutted the two transistor 5vsb circuit and replaced it with a DM311 chip and circuit. Made a nice little heat sink from a piece of copper flashing. And....I added a line filter with X and Y capacitors. Now it looks like a "half" decent power supply.

[everell]

Re: Fun with fixing I-Micro power supplies

The second "fixer-upper" is also rated for 450 watts according to the case. I used a second set of the "better" heat sinks for this one. Also removed the ZWCON main capacitors and replaced them with Fuhjyyu 680 uF/200 volt capacitors. Added the three coils in the output pi filters, and replaced all output capacitors with "better" measured output pull-out capacitors. I really didn't want to spend money to put super good capacitors in a power supply which I know is not going to do its rated 450 watts. Added line filter transformer and X and Y capacitors. Gutted the two transistor 5vsb circuit and installed a Viper 22A smd chip. My thanks to ldsishere for making the circuit board. I installed two D209L pull-out switching transistors. They were singing to me, so replaced them with a pair of pull-out 2625 transistors. Now this power supply works.

[everell]

Re: Fun with fixing I-Micro power supplies

I had my doubts, but I tested both of these "rebuilt" power supplies by powering up a Gigabyte motherboard with 3.2 Gig Prescott Pentium 4 cpu and 2 GB of PC3200 memory and a PCI express video card. I was expecting them to either not turn on at all or at least give a few hick-ups. Both power supplies ran the motherboard without giving any trouble.

Both also powered up fine on my Pentium 3 Biostar M6VLQ test mother board.

[everell]

Re: Fun with fixing I-Micro power supplies

Found three more IMicro's. One had a pc board like the ones in my first post. The other two had yet a fourth version of pc board layout. All three of these had one capacitor for each output voltage, no room for a coil and second capacitor to form a pi filter. So all will go to the scrap pile. The thing that caught my attention to this "fourth" pc board layout is that not only did it NOT have a line filter, it has no place to put it. Take a close look at the pictures. Nothing on the pc board layout for a line filter! How can you possibly make this power supply better.....when the pc board can not accomodate pi filters on the output and line filter on the input??? Cheap.....no wonder these things fail quickly.

[everell]

Re: Fun with fixing I-Micro power supplies

The IMicron pc board from my scrap pile (shown earlier) does have room for line input filter and output pi filters. Maybe there is some hope for this one! So lets see if I can find enough parts to put it together properly! Found line filter components from one of the less desirable IMicron units. Found three pi filter coils in my pull out parts collection. From my pull out capacitors, found a pair of 2200 uF/16 volt capacitors for the 12 volt output, a pair of 3300 uF/10 volt for the 5 volt output, and a pair of 2200 uF/6.3 volt for the 3.3 volt output. Found a pair of 1000 uF/200 volt caps for the main input capacitors. Installed a pullout 7500 pwm chip, and a few other missing parts. Now it looks much better.

[PeteS in CA]

Re: Fun with fixing I-Micro power supplies

I guess if you have a large pack-ratted stash of salvaged good components and heatsinks you could re-manufacture almost any POS into decent 300-350 watt P/Ss. The original heatsinks would have put the realistic (= no shrapnel) power limit around 200W.

[kc8adu]

Re: Fun with fixing I-Micro power supplies

only if your time is worth nothing....

I guess if you have a large pack-ratted stash of salvaged good components and heatsinks you could re-manufacture almost any POS into decent 300-350 watt P/Ss. The original heatsinks would have put the realistic (= no shrapnel) power limit around 200W.

[stj]

Re: Fun with fixing I-Micro power supplies

i dont understand why anybody would spend any time on these things.
i would just keep the wire-ended fuse and any thermal pads and bin the rest.

[ben7]

Re: Fun with fixing I-Micro power supplies

i dont understand why anybody would spend any time on these things.
i would just keep the wire-ended fuse and any thermal pads and bin the rest.

Eh some people enjoy doing this. Just interesting to see if it is possible to make these work decently. Like, eh, to see what it takes. Hey, you can learn in the process of doing so
And also enjoy some fireworks too on occasion xD

I do agree it could be a waste of time, but it all depends of how much time you have in the first place.

LOL That power supply with no EMI filtering on the PCB.
My only other guess as to why they did that is because their intentions were to use an external EMI filter. But being cheap... who knows what they were thinking.

-Ben

[stj]

Re: Fun with fixing I-Micro power supplies

RE the EMI - i think they just didnt care.

as for the rest of it, i could understand trying to get a decent 400w supply to give 500,
but trying to get junk to live up to the label is a different matter!

[ben7]

Re: Fun with fixing I-Micro power supplies

but trying to get junk to live up to the label is a different matter!

Yeah LOL.

Might as well just start fresh, and design your own PSU xD

[Pentium4]

Re: Fun with fixing I-Micro power supplies

i dont understand why anybody would spend any time on these things.
i would just keep the wire-ended fuse and any thermal pads and bin the rest.

It's fun Plus, not every computer needs a lot of watts. If it's a Core 2 with no video card, and a single hard drive, it doesn't need a lot of juice.

[everell]

Re: Fun with fixing I-Micro power supplies

As per the first post, a computer shop salesman asked the question....why are so many IMicro power supplies failing right out of the box? Based on what we have seen so far, what could we tell him?

1. Only one had emi line filter.
2. Main input capacitors have too low value AND measure only 60% of marked value.
3. Switching transistors inadequate for advertised wattage
4. Switching transformer too small for advertised wattage
5. No pi output filters on any of them.
6. Output filter capacitor values too small, inadequate for advertised wattage.

Two were "fixed" or "enhanced" and I am confident they will probably do half of their advertised wattage. I am working on one more.....I like to play with power supplies.

Anyone have anything else to say to the computer shop salesman?

[momaka]

Re: Fun with fixing I-Micro power supplies

Nice work everell! (as usual )

Looking at the pictures, I see some reused Teapo and Jamicon caps. These are from Bestec PSUs, aren't they, hehe .

I guess what we can get out of this thread is: if you have five or more gutless power supplies, you just *might* have enough parts to build one proper PSU (more or less) to handle about 250W in spec

Eh some people enjoy doing this. Just interesting to see if it is possible to make these work decently.

+1

Obviously, for anyone who is doing this, it's not to make money. More of a hobby or fun for a rainy day.
It is also a fine way to get your hands on fixing electronics and even understanding how they work. When I started getting a little deeper into learning electronics, I started with these cheap PSUs. Their "simplicity" (or lack of guts, if you will ) makes it a little more obvious to see what is going on.

Also, everell is known as one of the PSU thinkers on this forum . And he is good at it, too. That DM311 5VSB mod is cool after all . (pun here too?)

Plus, not every computer needs a lot of watts. If it's a Core 2 with no video card, and a single hard drive, it doesn't need a lot of juice.

Exactly!
I just put a barebones PC on my bench today - my experimental Intel-made HP DC7700 motherboard with a single 2.5" laptop SATA HDD and everything integrated. Guess what? With a Core 2 Duo E2160, the PC was pulling 80W tops! With a Radeon HD2400, that system won't top out more than 100-110W. I think many PSUs can handle that - even the very gutless ones (okay... maybe not the ones with a diodes-on-a-bracket "rectifier" for the 12V rail ). No wonder they get away with it.

Now try that with a dual core Pentium D . Or a dual socket 939 motherboard with two FX-60 CPUs (my dream system from back in the earlier days of multi-processor PCs ).

[stj]

Re: Fun with fixing I-Micro power supplies

As per the first post, a computer shop salesman asked the question....why are so many IMicro power supplies failing right out of the box? Based on what we have seen so far, what could we tell him?

1. Only one had emi line filter.
2. Main input capacitors have too low value AND measure only 60% of marked value.
3. Switching transistors inadequate for advertised wattage
4. Switching transformer too small for advertised wattage
5. No pi output filters on any of them.
6. Output filter capacitor values too small, inadequate for advertised wattage.

Two were "fixed" or "enhanced" and I am confident they will probably do half of their advertised wattage. I am working on one more.....I like to play with power supplies.

Anyone have anything else to say to the computer shop salesman?

you cant tell a salesman any of that - he wont know what your talking about.
just say that they are shit and the parts used are substandard junk.

[Pentium4]

Re: Fun with fixing I-Micro power supplies

^ It's kinda fun to see them get uncomfortable at all the knowledge you're giving them that they will never absorb or retain

[everell]

Re: Fun with fixing I-Micro power supplies

I finished putting the parts in my last "decent" IMicro pc board. Plugged her in and the 5vsb came up just fine. Used a paper clip to short the green wire to ground to turn it on, and it went off like a sparkler on the fourth of July. Multiple popping sounds, lots of sparks, and some smoke before blowing the fuse. Not too sure if I will be able to resurrect it! Not sure why it went, but it was "just another cheapo pos power supply".