M-Audio Studiophile BX8a reference monitors

[whelanska]

My first post here... I don't really know what to specifically search for in regards to my question, so if this product/issue is covered elsewhere in this forum, just let me know.

I bought a pair of M-Audio BX8a monitors a couple years ago. I don't know much about the inner workings of speakers, amps, capacitors, etc. - I just know that these sounded pretty good when I bought them.

However, one of the speakers started sounding funny. I opened the back panel and found some brown ooze (electrolyte leakage + its effects?) at the base of the capacitors. After much searching, seems this might be due to the "plague."

Can I clean this board and replace the capacitors? Both speakers still work, but one of them is missing a ton of clarity. Hard to explain, no hissing, static or popping - it just doesn't sound right at all. When both monitors are on at the same time and at the same volume, it's hard to tell anything is wrong (assuming usage is for casual music listening - not music recording). The amount of ooze around my capacitors seems to be much greater than what I've seen in other photos, so I'm wondering if more ooze amounts to more serious problems.

I don't have experience with anything related to caps or soldering, etc. I have an aerospace engineer friend who could potentially assist me with the actual soldering and whatnot, but I've already gotten mixed opinions about the board being dead/toast/garbage or not from the few people I know personally who even know about this stuff. If this board is toast, I'd just trash the monitors because I have newer ones, but if it's not a lost cause to fix this board, I'd like to use the experience to learn more about this stuff, in case that influences any answers.

Thanks!

[mariushm]

Re: M-Audio Studiophile BX8a reference monitors

Wow, those are really leaking..... surprised the speakers still work !

The electrolyte (that brownish substance) can conduct electricity and short components so you should really replace those capacitors and put new ones AFTER cleaning the boards a bit.

I don't have much experience with cleaning electrolyte from boards but I think isopropyl alcohol (or isopropanol, same stuff) would work.. Just wet some cotton tips with this special alcohol and carefully rub the burnt electrolyte off.

Please try to take out the whole board or at least pull it out a bit and write here what's written on the capacitors (all capacitors that have that brownish substance around) and we'll suggest what capacitors you should buy to replace these you have now.
They're definitely the cause of poor quality sound.

It would also help if we could see the whole board.

This board is a relatively simple one, without lots of layers, so it would be relatively easy to solder new capacitors. But if you never soldered before, it would help to have your friend around or at least you should watch a few tutorials about soldering before.
I can suggest a few videos to watch if you're interested, it's just too late for me to add them now to the post.

[lti]

Re: M-Audio Studiophile BX8a reference monitors

That looks like glue to me, but it looks like the big capacitor is bulging. I would replace every electrolytic capacitor in both speakers.

[whelanska]

Re: M-Audio Studiophile BX8a reference monitors

Thanks so much for the replies. I took more pictures of the board this morning. I'm putting a few in this thread, but there are a lot more on Google Photos, including more close-ups of the caps.

BX8a board photo album:
https://plus.google.com/photos/11392...N3m7_uOxbKgjgE).

The two larger oozing caps have this printed on them:
50 V
4700uF
LXC
(M) 105 degrees Celsius
VENT



The smaller two oozing caps have this printed on them (I think, hard to see):
-40+10
2200uF
LXC
(M) 105 degrees Celsius
VENT





Here's a shot of the full board:



I tried to clean the brown ooze with some alcohol on a cotton swab, but it didn't seem to do much. Definitely didn't start dissolving away. I tried to flake away some of the ooze with a knife, but thought it best to stop before I damaged something. I'm worried about scrubbing or touching any of the other components that are covered in ooze - how sensitive are the various resistors and other things on the board to being scrubbed with alcohol?

Here's a close-up of the ooze in case that helps to determine the best cleaning method:



Also, I opened up the "good" speaker, the one that still sounds normal, and the same caps are oozing brown stuff but to a much lesser extent.

[mariushm]

Re: M-Audio Studiophile BX8a reference monitors

Cool. So that brownish stuff may actually be glue and not electrolyte in which case you could leave it there.
There are some types of glue that become conductive when they're old and also turn to a darker color but I don't think that's the case here.

I can't figure out the brand of those capacitors just from the "LXC" code, so they're probably some Chinese ones, nothing special about them.

But you need to know the diameter of those capacitors so that new capacitors can fit.

For the 4700uF capacitors, measure the diameter and add a few mm, as much as you can think there is now around the current capacitors.

Depending on that diameter, the following would work :

22mm, 1000h@105c

http://www.digikey.com/product-detai...1362-ND/589103

22mm, 2000h@85c

http://www.digikey.com/product-detai...1133-ND/588874

20mm

http://www.digikey.com/product-detai...1115-ND/588856

18mm

http://www.digikey.com/product-detai...397-ND/3134353


---

For the 2200uF capacitor, look again at the capacitor and what's written on it and try to figure out the voltage ... should say 25v, 35v, 50v, 63v... without voltage rating it's hard to determine what may be proper.

For 50v capacitors, these will work

18mm diameter

http://www.digikey.com/product-detai...1623-ND/756139
http://www.digikey.com/product-detai...1960-ND/589701
http://www.digikey.com/product-detai...2018-ND/756534

16mm diam

http://www.digikey.com/product-detai...422-ND/3134378
http://www.digikey.com/product-detai...402-ND/3134358
http://www.digikey.com/product-detai...613-ND/2786988

For 35v you can use these:

16mm

http://www.digikey.com/product-detai...451-ND/2433585
http://www.digikey.com/product-detai...1596-ND/589337
http://www.digikey.com/product-detai...1589-ND/756105
http://www.digikey.com/product-detai...1879-ND/589620

12.5 mm

http://www.digikey.com/product-detai...450-ND/2433584

[lti]

Re: M-Audio Studiophile BX8a reference monitors

The two big caps are bulging. However, that would add background noise, not reduce sound quality. You might want to check the voltage across those two caps to make sure they didn't fail from running too close to (or over) their rated voltage.

Since the original caps are rated for 105°C, I wouldn't use 85°C caps.

[mariushm]

Re: M-Audio Studiophile BX8a reference monitors

I'm not very fond of recommending 85c capacitors, but there's not many 4700uF capacitors in stock at Digikey rated at 105c and - the only one is 22mm in diameter, in the first link.

I wouldn't use 85c, especially as they're right near the bridge rectifiers which will be quite warm. However, what I linked to is 2000 hours at 85c... who knows what rating those no-name capacitors had.

Could be 500 hours @ 105c which is pretty much about the same as 2000 hours at 85c. I can't tell from what's written on the caps, LXC tells me nothing.

Here's an alternate shop, which has a few more options:

http://www2.mouser.com/Passive-Compo...rature+Range|0

These will work as replacement for the 4700uF capacitor, just make sure the diameter works.

[budm]

Re: M-Audio Studiophile BX8a reference monitors

I think the glue should be removed, I can see some of the jumpers wire have some corrosion on them.

[whelanska]

Re: M-Audio Studiophile BX8a reference monitors

mariushm:
Thanks for the links, I'll check the capacitor widths tomorrow (don't have a millimeter ruler at the moment). Also, I had a closer look at the 2200uF capacitors and they have 35 V printed on the side.

lit:
My ears are pretty average and the speakers sound alright to me, but my musician friend who has a really great ear had mentioned hearing some extra noise when he tested them.

I read in an M-Audio forum that capacitors used in some of their products a couple years back might not have had enough "headroom." (Mentioned by a customer/user, not M-Audio tech support.) I can only generally understand what that means, but would it make sense to use a 50 V capacitor instead of another 35 V capacitor if the other specs are equal? I have no idea if doing that is possible/good/bad/stupid, just read about it on the internet!!

budm:
In general, how would I go about removing the glue? And how did it get all over? When the capacitors overheat or fail do they start melting glue inside the capacitor itself or was the glue from the board? I'm going to take a closer look for bulging inside the "good" monitor, but as of now the noticeable difference between the two monitors is the extra brown ooze in the bad one. I'm just worried about scrubbing/scraping the glue/board too hard and busting something.

Thanks again for all the help.

[mariushm]

Re: M-Audio Studiophile BX8a reference monitors

You can use capacitors rated for higher voltage, but they won't make any difference audio quality wise. If you can fit them on the board and they don't cost more, it won't hurt to use them.

In regards to "headroom" comment, there's a HUGE amount of "audiophoolery" with audio capacitors, as much as there is with hdmi cables and regular video cables.

For example, look at the datasheet of a classic, "audio" capacitor :

• ELNA developed new raw material for the separate paper which use a silk fibers.
Therefore, this capacitor can give you high grade sound for your audio design.
• Due to the silk fiber's pliability, the capacitor makes a dream of the high quality sound.
For examples:
• To relieve the music's vibration energy.
• To decrease the peak feeling sound at high compass and rough quality sound at middle compass.
• To increase massive sound at low compass.

To relieve the music vibration energy? What does that even mean? To decrease rough quality sound? Silk fiber pliability?

"All lead wires oxygen-free copper for extremely low distortion " - yeah, lead wires which get soldered to regular copper pc board with plain lead free solder. Those 2-3 mm of oxygen free copper wire are surely going to make a difference in the audio quality...

It's just marketing talk mostly in my opinion. You just have to think how much would these difference count, when the output of your audio amplifier goes through regular copper wires to a regular speaker.

There are SOME capacitors that are audio grade and it makes sense to use them in certain parts of amplifiers due to their technical characteristics but usually they're 10-47uF and they're not used in the power supply part of the amplifier.

In my opinion, for your broken capacitors, you just need to pick brand name ones, from reliable manufacturers with known reputation, so you won't have to repair the speakers again later.

[whelanska]

Re: M-Audio Studiophile BX8a reference monitors

Great, I think that clears it up - I think I'll keep it simple and stick with the same size/voltage capacitors and just make sure they're from a good brand and high quality.

My only remaining concern is the glue/ooze/electrolyte on the board. Since the consensus seems to be that this is probably glue, is this all from the manufacturer? Or was it melted from around the capacitors as they got hot? A friend of mine said if it's glue it was probably put there by the manufacturer and I should leave it be, but just doesn't look right to me at all...

I feel if it's possible I should get as much of that off the board and away from other components as I can. Any best techniques for removing that stuff? I tried a sharp knife but it didn't work very well and I already scratched the green part of the board a little bit.

[budm]

Re: M-Audio Studiophile BX8a reference monitors

@mariushm: this must be the same guy the writes speeches for Presidents and Politicians I just heard tonight, LOL!

[djexit]

Re: M-Audio Studiophile BX8a reference monitors

did it work? i have 3 of these and it seems like its the same problem on all of them

[Neil Dvorak]

Re: M-Audio Studiophile BX8a reference monitors

My M-AUDIO AV30 LOST ALMOST ALL GAIN. One filter cap had blown up, and several others, used as DC blocking, had lost virtually all their capacity. Will replace all electrolytics with high temp (105C) ones soon. The brown stuff is glue by the way.
-ND

[ben7]

Re: M-Audio Studiophile BX8a reference monitors

My M-AUDIO AV30 LOST ALMOST ALL GAIN. One filter cap had blown up, and several others, used as DC blocking, had lost virtually all their capacity. Will replace all electrolytics with high temp (105C) ones soon. The brown stuff is glue by the way.
-ND

Pictures? xD

[SnowKitteh]

Re: M-Audio Studiophile BX8a reference monitors

i repaired some AV30s a while back for my roomie, bad caps all over the board and the cap failure had caused a zener diode to explode. there were some burnt traces i had to repair as well. i'd recommend not using those speakers anymore till you replace the caps. running them like that could end up causing damage to other components as the capacitors get worse.

[darkdream]

Re: M-Audio Studiophile BX8a reference monitors

I really want to know what happened to your speakers? I have same problems. i want to change my caps with high-grade audio caps. What is your experienced?