Bestec....the next generation

[everell]

Re: Bestec....the next generation

Here is another TFX0250 Bestec with a burnt group regulation coil, also pc board burn damage. Perhaps this is a trend.

[Behemot]

Re: Bestec....the next generation

May also be bad wire insulation.

Anyway, is there any way how to find what material is a coil made from? I got lots of coils from different places (input filtering, common secondary coils, PFC coils). If some coil burns somewhere (and that happens), I may be able to just take different core and wind my own replacement but as the material properties differ, I am not sure if I can just pick up any toroid of right size no matter what it is made from…

[PeteS in CA]

Re: Bestec....the next generation

That inductor is definitely very much toasted - possible intra- or inter-winding shorts, magnetic properties of the core probably changed. The best I can suggest, briefly, is to carefully remove the inductor, keeping track of what wires went where, and then building a new one, using a new Micrometals core of the same size and -52 material (the original might have been -26 material, but this change will be benign at worst, and possibly improve thermal performance). Carefully duplicate each winding - wire size, winding order, number of turns, and phasing.

The other question, though, is why did the inductor fail. Bad fan and cooked itself? An overload in the computer system? Bad lytic caps (some of the output caps look tilted, possibly bad).

[senz_90]

Re: Bestec....the next generation

i don't know is it forbid or not to asking a price here. i just wanna ask what is price for a "regular" Bestec in USA? i means regular that the quality isn't too good but not the crappy one..so i can know the reasonable price for me before searching around town, maybe my town has a supplier for Bestec.

i have looked around and i see many people using Bestec. i just think if only i can get it from my town to open it.. i feel eager to see what is insidely.

[climbertx]

Re: Bestec....the next generation - problem with this PS

Next up is a Bestec TFX0250D5W. A smaller case but a 250 watt cutie. It has a 24 pin connector for the mother board. Three SATA connectors but no molex connectors, a floppy connector, and a four pin cpu connector. This power supply is probably for a low end economy computer.

Guys I got impressed with your hacking skills in the electronic field, this time I want to ask you about this.. please dont be rude with me, I'm not in the electronic field.. but when this customer power supply got crashed I think to open it just to make sure if there is some component that I can find locally and replace it (because replace the PS will take some days because shipping).

I dissasemble the PS and find a coil that seem to be damage, I attached pictures, ok

1st question.
Where can I find this kind of coil?, seems that my local electronic spare parts doesn't have it.

2nd question.
did you had some problem like this before? and if you already have it.. what is the probability that just the coil is the damaged component ?
(i mean if i replace the coil did it get damage again if some other component are also damage?)

thanks a lot for your help.

[Behemot]

Re: Bestec....the next generation

I'd say more ESR critical than capacitance critical…

[tom66]

Re: Bestec....the next generation

I highly doubt a 0.1uF ~ 1uF capacitor is going to be ESR critical.

[Behemot]

Re: Bestec....the next generation

I think so, pick up the ones with close ESR rather than capacity I guess.

[mockingbird]

Re: Bestec....the next generation

Newark doesn't have any good 0.1uF, 0.47uF or 1uF electrolytic caps... Can I use film caps instead?

[Behemot]

Re: Bestec....the next generation

If they are close enough ripple/ESR wise, than sure.

[OT]Does it have Pickard?[/OT]

[mockingbird]

Re: Bestec....the next generation

Does anyone know if I can use 50V 0.1uF caps instead of the three stock Jamicon TK 63V 0.1uF caps on this PSU? The choices of 63V replacements doesn't look promising.

One of them is right near the two big input filter caps, and the other two are on the secondary side.

[ben7]

Re: Bestec....the next generation

Firstly, I'm not sure if this thread is closed etc. anyway. I have a Bestec ATX-300-12Z Rev: CCR which works except, there is noise on the computer screen that seems to be worst at cold startup and when current is being drawn. That is, when the HD gets action, also I can hear "mouse zip" when I move the mouse I can "hear" the data flow through the speakers in the monitor.

Once the computer has been on for 30 mins, all settles down and everything seems OK.

All this sounds like the output caps in the PSU are in need of replacement - would you say my assumption is correct?

Might be the primary caps, but it is for sure some type of capacitor!

[mockingbird]

Re: Bestec....the next generation

I have one with a stock Chemicon there.

[tom66]

Re: Bestec....the next generation

C36 probably isn't failing due to external heat. It's on the output of a flyback and that has high ripple current under load. A lot of people like to charge their phones and such from USB when their PC is in standby which would be fine if the power supply used a proper capacitor. Seems CapXon/OST just can't handle much ripple current at all.

[itwentboom]

Re: Bestec....the next generation

Firstly, I'm not sure if this thread is closed etc. anyway. I have a Bestec ATX-300-12Z Rev: CCR which works except, there is noise on the computer screen that seems to be worst at cold startup and when current is being drawn. That is, when the HD gets action, also I can hear "mouse zip" when I move the mouse I can "hear" the data flow through the speakers in the monitor.

Once the computer has been on for 30 mins, all settles down and everything seems OK.

All this sounds like the output caps in the PSU are in need of replacement - would you say my assumption is correct?

[Steve.B]

Re: Bestec....the next generation

We posted at the same time everell. I did actually remove a load of that glue gunk they use, it was turning a nasty brown colour in places and was actually beginning to eat into some of the components. I also resoldered a lot of joints, mainly because i removed all the heat sinks and the large mosfets to check them out.

Maybe it was the resoldering and gunk removal that done the trick, but either way, it's living again. But like i say, if it plays up again i will recap with good caps, plus i will do the C36 mod that you done, very handy having that spare bit of pcb right in line with the tracks for that cap! Good idea that.

Anyway, thank you for your reply, appreciated mate.

[Steve.B]

Re: Bestec....the next generation

Just to let you know i got the little bugger working again. I went all over the board checking everything i was capable of checking, in the process i noticed the small 22uf 50v cap that was situated near to C36. And this one was even closer to that large diode, in fact it was actually glued to it with that insulation gunk they use. So i guessed that it might also be suspect.

I had a secondhand one in my box of bits, so fitted it just incase. Bingo! She fired up first time. I checked the voltages, all seemed good with the exception of my multimeter showing a .1 to .2 of a volt fluctuation on all lines. That was without any load. Having not worked on a ATX PSU before i can't comment on that, other than it may well have been down to my meter.

Either way i reclaimed my spare psu from my mates pc, and put his Bestec back in. I will leave it running for a few hours tomorrow, if ok he can have it back. If it gives up again i will then recap it properly.

Anyway, thanks again for your replies, they are very much appreciated i can assure you.

[everell]

Re: Bestec....the next generation

The starting point is to remove glue covering the components. I just recently fixed a Bestec ATX-300 12E which had the same symptoms you have described. Once the glue (and corrosion) was removed, the power supply came up running just fine. As the glue ages, it gives problems, and can shut the power supply down.

Next, measure the resistance of the output diodes. Typically they measure a very low resistance, but any that measure zero ohms indicate a short and will give the symptoms you describe.

[Steve.B]

Re: Bestec....the next generation

Thank you mariushm, that is good of you. I have already ordered the cap, so no problem with this one, but i will pm you if i do need another one for this board. Again, thank you.

[mariushm]

Re: Bestec....the next generation

If you need just a few capacitors I can mail you some from here in Romania - I order often from Farnell and Digikey and have some spares around..

You can paypal me the Farnell price + 1 pound for postage and thick envelope

I have the FM 2200uF/16v here but it is indeed 12.5x25 mm

Maybe you could settle with just 1500uF/16v Nichicon HM which is 10x20 mm (which i also have) - provided you don't load the 5v rail to the max it shouldn't be a problem in real life.