Smoking M-Audio bx5a - Capacitor blown?

[kcroy]

Hi - relatively new to electronic repairs .. is it apparent which elements here are damaged?

I was listening to these (used/new looking) and one speaker was set to 230 instead of 115v. It started smoking.. switched to proper voltage, but sounds like crap now.. not sure if it still smokes, didn't want to keep it on.

I'd prefer to fix if possible - I got the speakers for $100.. not interested in sinking money into them.

Any help appreciated!

http://img841.imageshack.us/img841/2...cf15911200.jpg

http://img691.imageshack.us/img691/8...cf15941200.jpg

-kcr

[shaddai]

That 6800uF capacitor looks like it got hot in the pics. Should be an easy fix, but I wouldn't know much more without poking around with a scope & a meter. Could've done something else to it without it being immediately visible..

todd

[Les]

So it was set to 230 and plugged in to 115?

Cleaning and replacing that 6800 uf cap is a very cheap and easy thing to try.

Check those two fuses too...

If semiconductor devices are blown I don't know if it would be worth the trouble unless you have proper test gear and a schematic, and really like to spend time repairing things.

[Remeniz]

Check out D6 and IC3.

If you compare D6 to D5 nearby, D6 looks like it's burnt. And IC3 has burn marks on it.

Just something to consider.

[S2udio]

Do you own a DMM ....Set to continuity or diode check...no power required
Just a soldering iron and flux
Component check familiarity helps...
Check diodes and reg /op amp/transistor junctions
...dead shorts,then lift on end to double check , (SMPS)
Of course this depends on circuit knowledge..or pass it on to a good tech
BTW most of that gunk is just taiwan glue...
And as for the smoked IC and diode ?
Check with a DMM !!
I find 60% of faults with no power applied !
The other 40% ,(Digital/bastard Analogue faults)need a more advanced approach.

[kcroy]

Originally Posted by S2udio

Do you own a DMM ....Set to continuity or diode check...no power required
approach.

Thanks everyone - going to look into your comments, and see what I can test myself. Will report back !

[kcroy]

Originally Posted by Les

So it was set to 230 and plugged in to 115?.

Correct - can that actually damage it? I wouldn't think that would do it.

Cleaning and replacing that 6800 uf cap is a very cheap and easy thing to try.

Check those two fuses too...

If semiconductor devices are blown I don't know if it would be worth the trouble unless you have proper test gear and a schematic, and really like to spend time repairing things.

Fuses look good. I'll try and swap the cap, if nothing else just to get my feet wet.

[kcroy]

Originally Posted by Remeniz

Check out D6 and IC3.

If you compare D6 to D5 nearby, D6 looks like it's burnt. And IC3 has burn marks on it.

Just something to consider.

IC3 and IC2 look identical to me. What part of it looks burnt?

Having to learn some basics (soldering / unsoldering / testing caps and transistors...) any tips on good guides to start?

Is there an easy way to ID a problem on a board without going in and pulling/testing everything?

[Minion]

Having it set to 230v and plugging it into 115v shouldn"t Cause it to fry anything if the power supply is a Linear supply which is appears to be ..... All that would happen is the amp gets half the voltage it is expecting which might cause it to sound bad or not sound at all when set to 230v but it should work again when it"s set back to 115v .......

[kcroy]

Started working on this project again...

I pulled the cap, which is bad.

I pulled these two, but am having a hard time reading the mm

D5 and D6 give me different values depending which polarity I use. Resistors aren't supposed to have polarity right? Any thoughts on what is going on?

I'm getting some high values too, like 800 on the 2000M Ohms setting. does that = 800 M Ohms?

I tried to figure out what their rating _should_ be, but unsure how to find out what a red resistor with a gold band and black at one end is. It appears there is some tiny writing, but can't read it.

any help appreciated!

[._.]

Electronic color code - Wikipedia, the free encyclopedia

Just change what looks ruined and test it. If it works it works. componenets like resistors are easy to check. You will have to search on the internet on how to use your dmm and test components/soldering.

[a zombie]

Originally Posted by kcroy

D5 and D6 give me different values depending which polarity I use. Resistors aren't supposed to have polarity right? Any thoughts on what is going on?

D5 and D6 are diodes, not resistors, that is what the D stands for. You need to use the Diode test setting on your DMM

[kcroy]

Originally Posted by a zombie

D5 and D6 are diodes, not resistors, that is what the D stands for. You need to use the Diode test setting on your DMM

haha awesome.. that would also explain how I get different resistances based on how many ohms I was testing for yeah? Was making me a bit batty.

Thanks! I really appreciate all the help I've gotten on this project. Got me a copy of Electronics for Dummies, new tips for my 1950s yard sale Weller Solderer, and am going to town.

If anyone else has come here looking for help with their m-audio speaker, I also recommend this thread!

one of my BX5a died on me :( [Archive] - The Official M-Audio User Forums

Great tips on fixing these caps.. I guess lots of people have problems with them on the Bx5a. I'm going to cross post this thread when I finish my project.

[kcroy]

Originally Posted by Remeniz

Check out D6 and IC3.

If you compare D6 to D5 nearby, D6 looks like it's burnt. And IC3 has burn marks on it.

Just something to consider.

D6 and D5 have the same values (~.6v drop), so assuming those guys are working. Still trying to ID the diode.

Regarding IC3.. It looks like it says

4850D
JRC
5072x (x= C, 0, G) not sure which

RC 4850 seems like it might be the match: RC4580 datasheet, Pinout ,application circuits Dual Audio Operational Amplifier

but I don't see anything that matches the "D". and Have no idea how 5072x would fit in.

Any tips on IDing this guy?