Bestec ATX100-5 no +5VSB

[ben7]

Re: Bestec ATX100-5 no +5VSB

I had a Powerman psu which blew out the 5vsb transformer....so, yes it does happen. I put a want ad for a replacement transformer on this forum, and nobody responded having one. So my solution was to build an add-on board with the complete 5vsb circuit using a transformer from a badly burnt Fortron psu. You can see how I did it at this thread:

https://www.badcaps.net/forum/showth...light=powerman

I will agree that your transformer is probably bad. You can try looking for one at Radio Shack, or ebay, but doubt you will find one. You can try advertising to find a complete psu like yours and buy it for parts. This model looks like such an older one I doubt you will have much luck. If you do manage to find a replacement transformer, that two transistor circuit is very tricky to repair. Most I have attempted to repair simply blew up again. Then you end up with two bad transformers. That is why I like to modify the 5vsb circuit with one of the pwm chips.

One thing is certain, never mention Radioshack! they don't sell electronics components anymore! only cellphones and tvs and crap...


Yeah I agree it will probably be best to make a new 5vsb smps instead of trying to fix it.

[everell]

Re: Bestec ATX100-5 no +5VSB

I had a Powerman psu which blew out the 5vsb transformer....so, yes it does happen. I put a want ad for a replacement transformer on this forum, and nobody responded having one. So my solution was to build an add-on board with the complete 5vsb circuit using a transformer from a badly burnt Fortron psu. You can see how I did it at this thread:

https://www.badcaps.net/forum/showth...light=powerman

I will agree that your transformer is probably bad. You can try looking for one at Radio Shack, or ebay, but doubt you will find one. You can try advertising to find a complete psu like yours and buy it for parts. This model looks like such an older one I doubt you will have much luck. If you do manage to find a replacement transformer, that two transistor circuit is very tricky to repair. Most I have attempted to repair simply blew up again. Then you end up with two bad transformers. That is why I like to modify the 5vsb circuit with one of the pwm chips.

[ben7]

Re: Bestec ATX100-5 no +5VSB

Nah, I didn't use the resistance range, I check transistors in-circuit with the Diode Check function. 5VSB rectifier diode looks okay as well in Diode Check mode.

Why do you think the transformer is burnt out then? Its extremely rare for them to burn out.

[GnatGoSplat]

Re: Bestec ATX100-5 no +5VSB

Nah, I didn't use the resistance range, I check transistors in-circuit with the Diode Check function. 5VSB rectifier diode looks okay as well in Diode Check mode.

[ben7]

Re: Bestec ATX100-5 no +5VSB

Thanks, transistor looks fine using multimeter's diode check, though PSU is probably destined for the junk bin if I can't get a transformer for it.

Don't assume all the pins will have some resistance between each other!
There are two windings on the primary side, one for the switching input, and one for feedback.

Can you check the diode that rectifies the 5vsb? That might be bad.

[GnatGoSplat]

Re: Bestec ATX100-5 no +5VSB

Thanks, transistor looks fine using multimeter's diode check, though PSU is probably destined for the junk bin if I can't get a transformer for it.

[ben7]

Re: Bestec ATX100-5 no +5VSB

Do you mean 3rd from left? If so, that's supposed to just be a nub (no hole for it on the PCB). I think it's supposed to be an unused center tap for the 1st and 2nd pins from left. I've attached a closer pic so you can see what I mean.

Ah yeah nevermind...

Check the transistors in the 5vsb circuit, especially the one on the heatsink.

[GnatGoSplat]

Re: Bestec ATX100-5 no +5VSB

Looks like the pin came out of the transformer, better solder that back on and re-attach the wires to the pin!

Check the transistors in the 5vsb primary circuit.

Do you mean 3rd from left? If so, that's supposed to just be a nub (no hole for it on the PCB). I think it's supposed to be an unused center tap for the 1st and 2nd pins from left. I've attached a closer pic so you can see what I mean.

[ben7]

Re: Bestec ATX100-5 no +5VSB

It's a MicroATX sized PSU, OEM for HP. Has an HP p/n on it 5184-2191. A coworker gave it to me years ago because he knew I liked to tinker. Original problem I think was the fan was too noisy, so I dismantled and lubed the fan. Found a few bloated caps while I had it open and replaced them with stuff from my junk bin.

Numbers on the transformer looks like T-ATX-100T2I 00 44 CICB, but I've also included pics of it.

Yes, it looks like a two transistor 5VSB to me. I know Bestec is crap, but I have a hard time trashing anything because I hate waste. That, and I actually do need a small mATX sized PSU!

Looks like the pin came out of the transformer, better solder that back on and re-attach the wires to the pin!

Check the transistors in the 5vsb primary circuit.

[retiredcaps]

Re: Bestec ATX100-5 no +5VSB

I have never seen a Bestec of this model.

I saw a video of this about 1 year ago on the CubeComputerChannel

http://www.youtube.com/watch?v=Prmmd1tHV0Y&feature=plcp

[GnatGoSplat]

Re: Bestec ATX100-5 no +5VSB

It's a MicroATX sized PSU, OEM for HP. Has an HP p/n on it 5184-2191. A coworker gave it to me years ago because he knew I liked to tinker. Original problem I think was the fan was too noisy, so I dismantled and lubed the fan. Found a few bloated caps while I had it open and replaced them with stuff from my junk bin.

Numbers on the transformer looks like T-ATX-100T2I 00 44 CICB, but I've also included pics of it.

Yes, it looks like a two transistor 5VSB to me. I know Bestec is crap, but I have a hard time trashing anything because I hate waste. That, and I actually do need a small mATX sized PSU!

[everell]

Re: Bestec ATX100-5 no +5VSB

I have never seen a Bestec of this model. Could you post some pictures please.

The 5vsb transformer might be the same as the Bestec ATX-250 12E or 12Z. So tell us the numbers on the top of the transformer (or a picture of the top of the transformer).

From what you have said, it sounds like the 5vsb is a two transistor circuit with a blown transformer. If you really want it fixed........sure, why not. Most people on this forum throw away anything with Bestec on the label. Oh well................

[GnatGoSplat]

I was using this on a Mini ITX Hackintosh for years, and then one day I plugged it in after a few months of non-use and some magic smoke came out. I opened it and couldn't find anything burned. Checked for shorted semiconductors and bad caps, and found none (recapped it a few years back).
No +5VSB, but fuse is good and there is primary input voltage.

I identify what I believe to be the primary coil pins of the 5VSB transformer, one pin connected to + at the rectifier/input caps, and other pin connected to Collector of a TO-220 heatsinked 2SC4020 NPN transistor whose emitter is connected to - at rectifier/input caps through a 4.3ohm series resistor, so I presume this to be the 5VSB switcher. However, there is no continuity across these 2 pins on the transformer. One of the pins does have continuity to a little nub that looks like a pin cut off (center tap, I would guess, as it has 2 tiny copper wires going to it), but the other (that goes to the switcher) has no continuity to the nub or any other pin.

Does this also sound like a blown 5VSB transformer to you experts?

If so, can I get a 5VSB transformer any place, or is this the end of the line for this PSU?