Fun with fixing I-Micro power supplies

[goodpsusearch]

Re: Fun with fixing I-Micro power supplies

Wait.

Taking semi decent psus and turning them to decent 300 watters is fun and entertaining and you can use them in a usual core duo machine in the end.

On the other hand, when the psu is badly designed, for example having space on secondary for only 1 output cap per rail and no coil, then why bother? Who would trust even a Pentium 4 on a psu like that?

[Behemot]

Re: Fun with fixing I-Micro power supplies

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.

I can understand all that. But taking the whole picture, when this thing has tragic efficiency no matter what you do, and that bloody time you put into it, it is just so wasted. In two years some better PSU with higher efficiency will pay itself on electricity. Maybe even several times.

Oh BTW everell, seems that you are cheaping it out, too That wire jumepr does not look like thermistor to me

[kaboom]

Re: Fun with fixing I-Micro power supplies

replace the two 2sc945/1815s and any 4148s on the cold side of the driver tx

[ben7]

Re: Fun with fixing I-Micro power supplies

So.....a few parts replaced here and there and back for more testing. This picture shows the repaired pc board. Initial power up and the 5vsb is again working. Voltage across the main capacitors measured 332 volts. PS-on switch turned on and nothing. At least it didn't blow up! No fan twitch, no outputs, nothing. Serious troubleshooting to follow..........

Well the short circuit might have burnt out a winding in the main transformer or the driver transformer.

[everell]

Re: Fun with fixing I-Micro power supplies

So.....a few parts replaced here and there and back for more testing. This picture shows the repaired pc board. Initial power up and the 5vsb is again working. Voltage across the main capacitors measured 332 volts. PS-on switch turned on and nothing. At least it didn't blow up! No fan twitch, no outputs, nothing. Serious troubleshooting to follow..........

[everell]

Re: Fun with fixing I-Micro power supplies

I don't see any burnt spots.

OK......here are the pictures of the "burnt spots".You can see that several resistors and diodes are burnt. Both switching transistors were shorted. One of the switching transistors has smoke showing damage to it. The transistor without any smoke on it had even more severe damage.....when I took it apart the insulation pad had smoke damage under the transistor. The back of the transistor at the mounting hole had arc damage. The insulation "button" showed some melting and was fused to the transistor mounting hole. Most likely an insulation breakdown, short, and arcing on this transistor was the main culprit for this failure. Yes, it did take out the fuse.

[everell]

Re: Fun with fixing I-Micro power supplies

Here is the last picture I took of this IMicro before powering it up.....before it blew.....

[Pentium4]

Re: Fun with fixing I-Micro power supplies

Did the switchers blow? What does the underside look like?

[momaka]

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.

You need to build yourself a incandescent dim bulb tester. It should help you save A LOT of fuses from blowing in the future.
Details:
https://www.badcaps.net/forum/showpo...4&postcount=70

[ben7]

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".

I don't see any burnt spots.

[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".

[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

[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.

[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 ).

[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?

[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.

[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

[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

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

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.