AcBel 9841 problems

[golemmaster]

My brother has G4 (not mirror door). I think it's the gigabit version.
The AcBel 9841-291 power supply stopped working. No power, no fan twitch. I did some searching and read that the little 10uF, 2.2uF on a couple daughter boards go bad. I checked and yes they were out of spec and open. Also some small 100uF and 47uF on the main board were out of spec. All the big caps were good brands and are in good shape. (I have a ESR-micro 3.1) I replaced those little caps and the power supply powers-on ok with good voltages, but something is making a high pitched whine that gets louder with time (and, I'm guessing, heat). The PS powers the computer ok for a while but shuts off after a time. The sound is ignorable but I'm mentioning it as a possible clue as to what's going on.
Any guesses?

[Toasty]

Re: AcBel 9841 problems

This is the API9841-291, correct?

Photos are a plus. Please use the attachment function under "Go Advanced" button.

What brands/series caps did you use? The wrong types will cause the problems you describe. Please include the -original- caps specs.

[golemmaster]

Re: AcBel 9841 problems

Yes. API-9841-291
Old caps on the daughter boards: three 10uF 50v Lelon H024, 2.2uF 50v Lelon H028,
two 100uF 25v Lelon H028, 47uF 50v Lelon H016
New ones: The 2.2 uF is nichicon B1040, 10uF is NTE 092A
The 100uF nichicon B1004 and the 47uF are NTE 112A
I tested all of them before installation. This is the second recap. The first time I used good but used nichicons. It made noise so I recapped with new. I know the name NTE but not their cap quality.

I mis-remembered about the "big" caps. Sorry.
There are a couple what I think are UCC (a squashed shield emblem)680 35v, 220 35v. The output caps are TEAPO 6.3 and 15v. The mains look like Hitachi (kind of a bulls-eye emblem) 820uf 200vdc.
I did remove all those caps and checked them out of circuit. There is a resistor that got very hot and browned the board. I touched up solder joints.
There is one more daughter board. The fan connects to it. I didn't check anything on that one. It has 33, 47 and 0.47uF Lelon.

I'll post pics when I can go get some lithium AA. My old digital camera is very hungry and eats even the best alkaline battery in no time.

[Toasty]

Re: AcBel 9841 problems

Lelon H024 & H028 are date/manufacturing codes. Same with B1040 and 092A.

Your series codes are typically in the same line or very near the temperature line.

i.e.- Lelon RGA series. Lines would appear as such:

RGA105°C
H024(M)

Lelon page: http://www.lelon.com.tw/index.php - Follow "Products" for aluminum low ESR caps.

NTE does not make a low ESR line that I know of. That would be my first replacements. You need to match or exceed OEM when it comes to these caps. Otherwise, squealing and shutdown.

[golemmaster]

Re: AcBel 9841 problems

all values of Lelon say "(M)"

2.2 uF is nichicon PW(M)
100uF nichicon HE(M)
The NTEs have nothing recognizable on he cap. Maybe the part number on the package. VHT47M50, NE10M50AA-BU.

[Toasty]

Re: AcBel 9841 problems

(M) is the tolerance = 20% (standard)

PW and HE are good choices.

As I said, NTE doesn't make a low ESR cap. Just general purpose. Those need to be replaced.

[golemmaster]

Re: AcBel 9841 problems

That's all the Lelon caps have on them.
I tried other good caps before the NTEs with the same whine and shut off. What's the next step after eliminating those caps?
I'll get some pics as soon as I can.

[Toasty]

Re: AcBel 9841 problems

Localize the whine with your ears. Use a paper towel tube as a stethoscope. Then work in that area.

[golemmaster]

Re: AcBel 9841 problems

This is the PS I'm dealing with.
I could only get a few shots before the cheapo batteries ran dry.
More as I can get them....

[golemmaster]

Re: AcBel 9841 problems

The whine is very high pitched and sounds as though it's coming from everywhere. I'll try to locate.

[Toasty]

Re: AcBel 9841 problems

How are the voltages after the cap replacements. I would look at the output caps for replacement now. Not a fan of Teapo. They look good, but may be way off on ESR. One gone high on ESR will cause the whine.

[Longbow]

Re: AcBel 9841 problems

If you have found faulty 2.2 uf capacitors, then replace them. In my experience anything that says 2.2 uf or below should immediately be tested, because the small value caps are the most likely to lose value over time. Good advice from Toasty, check your secondary filters as one or more are probably faulty. My personal advice is to follow correct troubleshooting procedure: locate and replace obviously faulty parts and retest. Do not replace every electrolytic capacitor in the power supply just because you don't like the label. Your parts bill would probably exceed the value of the supply, not to mention the time required to do this job. I would also connect a simple power supply load (commonly available - plugs right in) otherwise you may get strange results when testing. Does this supply have a conveniently available schematic?

[golemmaster]

Re: AcBel 9841 problems

Also... When AC is applied, the 28v standby works fine. The sound doesn't occur until I turn on the switch to provide 12,5,3.3 etc
Is it normal for one of the heat sinks to have mains AC on it? Only one of the two support tabs that plug into the board is connected to a circuit of some kind, so it's not used as a bus.
The whine is very high pitched and is difficult to locate but I think it's coming from the area of the smaller transformer, or the nearby 2SK2765 mosfet, or something else nearby. There is a resistor that gets very hot nearby too. Hot enough to brown the PCB. Next to it is a ceramic cap 222K 1KV (measures 2.33 nF ?) and what looks like film cap BC 103J that is brown where another on the board is green.
What would be an acceptable ESR for a 47uF 50V in an application like this?

My apologies for what may be useless info. Please excuse my desperate blind stabbing at the darkness that is my knowledge and experience. :P

[Toasty]

Re: AcBel 9841 problems

>>Is it normal for one of the heat sinks to have mains AC on it?<<

Yes. Did you find that out the hard way??

Is the 5v standby working and in spec?

Rubycon YXF behind gray wire been tested? Others to check/replace are the 2 caps between the small trafo and the 1st heatsink, and between the trafo and the 2nd heatsink. Tough to see in the pics as it's very dark in there.

[golemmaster]

Re: AcBel 9841 problems

The 1000uF 6.3v Rubycon YXF measures 948uF 0.08ESR. That's OK, right?
The two caps are new Nichicon HE. The other one is a new NTE. (I know. I know.)
The more I messed with it and turn it on and off, the shorter it stays on.
It won't stay on longer than a couple seconds now. It makes the hissing noise and then shuts off. I think the noise is around that heat sink but maybe on the other end of it.
The fact that I seem to have permanent tinnitus makes it even harder to locate the noise.

[Toasty]

Re: AcBel 9841 problems

The Rubycon's ESR is fine.

Replace the NTE and see.

[golemmaster]

Re: AcBel 9841 problems

It's in pieces right now. Here are some pics.

[golemmaster]

Re: AcBel 9841 problems

I notice the 28v standby is always on even when it hisses and shuts off.

[Toasty]

Re: AcBel 9841 problems

What about the 5vsb?

[golemmaster]

Re: AcBel 9841 problems

There is no 5vsb that I see. Not listed on the label either.