ANTEC Basiq BP500U - test transformer?

[GnatGoSplat]

I have a blown ANTEC Basiq BP500U. One day I turned it on, and it buzzed loudly and the computer didn't turn on, so I quickly shut off the power switch. Then when I flipped the power switch back on, it blew my house circuit breaker and also its built-in fuse.

I found both the Active PFC MOSFETs 20N60C3 were shorted. Some of the CapXon caps in the secondary stage were bloated. Secondary rectifiers and switching FETs all tested good. I had to test the rectifiers out of circuit because they looked shorted due to the secondary windings on the transformer. I tried replacing the Active PFC MOSFETs and was able to get a good +5VSB. However, when I powered on the PSU, I heard a brief squeal sound and then it was dead. It shorted one of the MOSFETs I just replaced and blew the fuse.

Could this be the transformer? Is there any way to test the transformer? The transformer looks shorted when I check it on my ohmmeter, but then a known good one does too so I'm really not sure how to test it.

[Th3_uN1Qu3]

Re: ANTEC Basiq BP500U - test transformer?

The transformer rarely fails. It isn't unheard of, but it's uncommon. Have you replaced the capacitors before changing the active PFC mosfets? Speaking of which, any burn marks on the active PFC coil? That is a lot more likely to fail than the transformer.

Use a 100W lightbulb in series with the PSU to keep from blowing stuff up. The bulb should glow dimly when the PSU is turned on. If it lights up at full brightness you have a short somewhere.

[GnatGoSplat]

Re: ANTEC Basiq BP500U - test transformer?

No, I hadn't replaced the capacitors yet. I was thinking since they were on the output side, that they would result in poor quality output but not be responsible for the PSU shorting out. I was planning to replace them IF replacing the MOSFETs worked, but it didn't. No burn marks on the active PFC coil. Could that cause this problem? I thought the active PFC circuit has to be functioning to get a good +5VSB, is this not the case?

I wish I had used the 100W lightbulb! I knew better, I'd always used the bulb in place of the fuse when working on CRT TVs long ago, but this time I was over-confident so I didn't bother to hunt for it. It was a costly mistake, those MOSFETs are expensive.

[Th3_uN1Qu3]

Re: ANTEC Basiq BP500U - test transformer?

On almost all power supplies the 5vsb supply works directly off the mains and only the main supply is behind the active PFC circuit. The reason probably being that the cheap material they use for the PFC inductor runs warm at all times and needs the cooling provided by the fan.

[momaka]

Re: ANTEC Basiq BP500U - test transformer?

Check the main 400v cap. They usually don't give problems, but in APFC PSUs they can. If I remember correctly, there were a few cases here on BCN where people actually had the APFC fail due to CapXon (or was it OST?) mains caps going open-circuit. Either way, it's definitely worth checking if you have a capacitance meter.

[GnatGoSplat]

Re: ANTEC Basiq BP500U - test transformer?

I could almost swear I had checked it before, but I re-checked the 400V cap and it is completely open. No capacitance, no ESR.
It's a CapXon. If this cap goes open, is it typical that it should immediately short the MOSFETs?

[c_hegge]

Re: ANTEC Basiq BP500U - test transformer?

Considering that no cap means that the voltage from the PFC won't be filtered, it wouldn't surprise me.

[Th3_uN1Qu3]

Re: ANTEC Basiq BP500U - test transformer?

I could almost swear I had checked it before, but I re-checked the 400V cap and it is completely open. No capacitance, no ESR.
It's a CapXon. If this cap goes open, is it typical that it should immediately short the MOSFETs?

Yes. Because the energy in the PFC inductor now has nowhere to go.

[GnatGoSplat]

Re: ANTEC Basiq BP500U - test transformer?

Thanks, I believe that was it.
One of the MOSFETs was still good, so I removed the shorted one and temporarily installed a 390uF cap, this time using the 100W bulb instead of a fuse. The PSU was able to come on with no load and I checked all voltages, +3.3V, +12V, +5V, -12V, all look good.

There is still a slight squealing sound which could be due to the bad caps in the secondary stage, will they still squeal with no load?
I've also noticed significant inrush current that lights up the bulb pretty bright for about 2-3 seconds when the PSU is cold, but only a split second if the PSU hasn't been off long. Is this normal behavior?
Also, how critical is the capacitance of the main cap? 390uF worked, but the original was 330uF. Newer versions of this PSU use 390uF, but I assume that cap is matched to the coil, and the newer versions do use a slightly different coil. If it's not critical, would there be any benefit to a larger cap?

[Th3_uN1Qu3]

Re: ANTEC Basiq BP500U - test transformer?

Power supplies will generally squeal when there is no load, if it squeals under load it means there's something wrong with the compensation of the control circuit. And yes it is common for bad caps to cause squealing because they change the properties of the output filter when they go bad.

The inrush current is normal. The power supply has a NTC thermistor after the fuse, which deals with this. It has a high initial resistance thus limiting the inrush, then when it heats up its resistance becomes insignificant. By contrast, a bulb acts as a PTC thermistor - its initial resistance is very low, and the higher the current passed thru it, the brighter it will light, and the more it will limit.

The cap value isn't critical - a larger cap can only improve things. The only downside to a larger cap is that it'll take longer to charge from a cold start - therefore you get a higher inrush current. If your house electrical is wired properly this is no reason to worry. After all, it's not like this is a washing machine or anything.

[GnatGoSplat]

Re: ANTEC Basiq BP500U - test transformer?

Thanks, I think all I need now that I'm confident it's fixable is one MOSFET, fuse, and to recap it.

This PSU lasted maybe 1-year, but was out of warranty due to having been stored for some time before use. It looks like CapXOns used in this PSU don't last, so I'll try to get some good ones that hopefully won't cost too much and exceed the cost of a new PSU.

[Th3_uN1Qu3]

Re: ANTEC Basiq BP500U - test transformer?

Post the series and sizes of those Capxons, and state your location in your profile. That way we can recommend some proper replacements and a parts distributor in your area. If you're in the US you can help support this site and buy from the badcaps.net online store.

[GnatGoSplat]

Re: ANTEC Basiq BP500U - test transformer?

I'm in the USA, it looks like only 2 of the caps in the secondary were swollen, I checked ESR and the non-swollen ones look okay, at least in-circuit. The 2 swollen ones test bad, they are both CapXon 2200uF 6.3V KF 105C, both on the 3.3V rail. Main is a CapXon 330uF 400V LP VENT 85C.
Other than that, I will need a T8AH250V ceramic fuse with solder leads and one 20N60C3 MOSFET, TO-220FP (insulated).
MOSFET will be hardest to find, they are OOS at Digi-Key and Mouser, I may have to pay extra to buy one from eBay unless I either try to cross-ref it to something else or use a standard TO-220 and insulator kit.

If I use a different MOSFET, do I need to try to match the RDS(on), delay, rise or fall times? Since they are in parallel, I wonder if it's critical that they load balance properly.

[c_hegge]

Re: ANTEC Basiq BP500U - test transformer?

I don't think topcat sells suitable replacements for them. These would probably work. Replace ALL capxon caps, bloated or not. In-circuit tests are unreliable and capxon are pure junk. Even if they are OK now, the won't be for much longer

NEVER use two different MOSFETs in a PSU. If you're gonna replace one with a diferent one, replace the other two. It is indeed critical that they balance properly.

[GnatGoSplat]

Re: ANTEC Basiq BP500U - test transformer?

Got my new parts from Digi-Key today, caps replaced with Nichicon HM (HE series were a bit too large diameter). Main line cap replaced with a 390uF 420V 105C Panasonic TS-HC. I had to use an uninsulated SPP20N60C3 MOSFET and a mica insulating kit because I couldn't find a SPA20N60C3 insulated, but it's electrically the same anyway.
So far so good, it's been running a few hours now.

Thanks for all the help! Wish I had as much luck with my FSP PSU.

[momaka]

Re: ANTEC Basiq BP500U - test transformer?

Got my new parts from Digi-Key today, caps replaced with Nichicon HM

That's a bit of a problem.
The ESR of Nichicon HM is way much lower than the CapXon KF. While your power supply may *seem* to work fine, it is most likely outputting a lot more ripple than it should. The reason behind that is because the caps in a power supply are matched with the inductors - they create a tuned circuit that is specifically built to filter noise from the power supply. Change the ESR too much and you can actually make ripple and noise worse than it was with the original crap caps. And generally speaking, Nichicon HM isn't suitable for power supplies.

Most motherboards are built fairly tough (in terms of how much ripple and noise they can handle before becoming unstable) and probably won't have a problem if there is extra ripple. But if you ever test a more picky motherboard, you may run into stability issues.

At least the new HMs won't give you any trouble in terms of reliability, though.

[PCBONEZ]

Re: ANTEC Basiq BP500U - test transformer?

I've run into FSP's with 8mm 2200uF KF and HM was the only option due to space.
I think the early Basiqs were FSP and he may have the same problem.
IIRC, the KF's were also extra long so the ESR would be lower than 'stock' KF in the data sheet.
.
Kind of the same situation as the damned 10mm 4700uF Fuhjyyus.
.

[GnatGoSplat]

Re: ANTEC Basiq BP500U - test transformer?

Yep, that's right, I needed 8mm. I may have to check the ripple next time I drag out the o-scope. Everything looks good and well within spec according to OCCT, but I don't know that the health monitor chip and OCCT has a good enough sample rate to accurately measure ripple (I'm gonna guess the answer is probably not).

[PCBONEZ]

Re: ANTEC Basiq BP500U - test transformer?

I don't know that the health monitor chip and OCCT has a good enough sample rate to accurately measure ripple (I'm gonna guess the answer is probably not).

Nope it doesn't. It's for DC. Response is way too slow.
.