Hi everyone! I'm a new (italian 😛) user, but i've always used this forum for all my audio project, this place is GOLD for all the people like us 😛
So... Soundstream Lil Wonder 4.620 (third generation), owned for almost 6 years and never a problem... till some days ago! I always used only two of the 4 channels available (connected to those http://www.maxaudio.com.my/images/uploads/MaxAudio@1131.jpg quite hard to find nowdays), but a week ago I decided to add a sub (275W RMS) connected in bridge mode on 3rd and 4th channel. For a couple of days everything was running flawlessly, till it started to go on protection mode randomly on ignition :/ (first a pop, and than... protection!) The problem was solved once i've unplugged the sub, but after two days, the second channel (left speaker) started to make a white noise (just like a direct current was applied to the cone)... and than... protection mode xD I switched the two woofers on the 3rd and 4th channel, but after the end of the day, the amp ended in protection mode anyways. Now it's in protection even with nothing connected to it (no speakers and no rca).
Once disassembled, i didn't found anything that was apparently burned or broken (look the attached photos), except for a black spot (burned flux?) around the flat cables on the small pcb.. but the wires are ok :S As you can see i've already desoldered some transistors, but so far, this ones are good... Any advice?
Sorry for the long post 😱 and thankyou for you patience 🙂
Greetings from Italy 😀,
Andrea Carbone
Here's the photos
View image: IMG 0043[1]
View image: IMG 0045
View image: IMG 0044
EDIT: just found this... it's coming from the cap?
http://postimg.org/image/62ldk6z9j/
So... Soundstream Lil Wonder 4.620 (third generation), owned for almost 6 years and never a problem... till some days ago! I always used only two of the 4 channels available (connected to those http://www.maxaudio.com.my/images/uploads/MaxAudio@1131.jpg quite hard to find nowdays), but a week ago I decided to add a sub (275W RMS) connected in bridge mode on 3rd and 4th channel. For a couple of days everything was running flawlessly, till it started to go on protection mode randomly on ignition :/ (first a pop, and than... protection!) The problem was solved once i've unplugged the sub, but after two days, the second channel (left speaker) started to make a white noise (just like a direct current was applied to the cone)... and than... protection mode xD I switched the two woofers on the 3rd and 4th channel, but after the end of the day, the amp ended in protection mode anyways. Now it's in protection even with nothing connected to it (no speakers and no rca).
Once disassembled, i didn't found anything that was apparently burned or broken (look the attached photos), except for a black spot (burned flux?) around the flat cables on the small pcb.. but the wires are ok :S As you can see i've already desoldered some transistors, but so far, this ones are good... Any advice?
Sorry for the long post 😱 and thankyou for you patience 🙂
Greetings from Italy 😀,
Andrea Carbone
Here's the photos
View image: IMG 0043[1]
View image: IMG 0045
View image: IMG 0044
EDIT: just found this... it's coming from the cap?
http://postimg.org/image/62ldk6z9j/
Last edited:
Did you see the cone push/pull to its limits? That's what DC would look like.
A couple of notes...
1. The substance around the wires is a fixative applied to prevent the wires from flexing at that point (which would cause premature breakage). The substance is OK when it's light in color but when it turns dark, it can become conductive AND corrosive and must be completely removed to eliminate it as a problem and to allow you to examine the wire or electrical components beneath it.
2. That board is a CEM board (not fiberglass). When you have a conductor go through the board AND have solder on both the top AND bottom of that conductor, it's a point that will not be reliable. Examples are one end of J18, J22 and the resistor next to C313... Generally, the best you can do is desolder the conductor, clean it and remove all solder from both sides of the board and re-solder the connections. These can cause all sorts of intermittent connections which can cause intermittent problems.
A couple of notes...
1. The substance around the wires is a fixative applied to prevent the wires from flexing at that point (which would cause premature breakage). The substance is OK when it's light in color but when it turns dark, it can become conductive AND corrosive and must be completely removed to eliminate it as a problem and to allow you to examine the wire or electrical components beneath it.
2. That board is a CEM board (not fiberglass). When you have a conductor go through the board AND have solder on both the top AND bottom of that conductor, it's a point that will not be reliable. Examples are one end of J18, J22 and the resistor next to C313... Generally, the best you can do is desolder the conductor, clean it and remove all solder from both sides of the board and re-solder the connections. These can cause all sorts of intermittent connections which can cause intermittent problems.
Thanks for the fast answer ^^
Yep, the cone was moving to its limits! after that, a pop, and than the protection mode.
So, i'm going to clean that black fixative and resolder all that type of connections (starting with the worst looking ones).
Oh, I forgot to mention an important thing... the first time i've disassembled the amp, there was a solder residue that was shortcutting pins 2 and three of the dual positive rectifier diode... it was actually soldered to them, and by the looking of that thing, i can tell for sure it wasn't intentionally
View image: IMG 0019[1]
Unfortunately removing that residue didn't change the situation :/ i'm checking right now that dual recrifier diode just in case
Tks again
Yep, the cone was moving to its limits! after that, a pop, and than the protection mode.
So, i'm going to clean that black fixative and resolder all that type of connections (starting with the worst looking ones).
Oh, I forgot to mention an important thing... the first time i've disassembled the amp, there was a solder residue that was shortcutting pins 2 and three of the dual positive rectifier diode... it was actually soldered to them, and by the looking of that thing, i can tell for sure it wasn't intentionally
View image: IMG 0019[1]
Unfortunately removing that residue didn't change the situation :/ i'm checking right now that dual recrifier diode just in case
Tks again
ok, i checked almost all the two sides soldering joints and cleaned the old fixative on the flats. I've tried to reconnect the amp, and on the second try it didn't went on protection! i checked if there was some dc on the channels, and 4th had it... a lot! And the value kept rising! Now i've desoldered the two output transistors of that channel (tip35c and tip36c), and both are good... What's the next thing i should check?
The solder bridge on the rectifier was not intentional. That should have caused excessive current draw if that power supply was functioning.
Check all of the op-amps to see if any have excessive DC on their output terminals.
Check all of the op-amps to see if any have excessive DC on their output terminals.
The op-amps are those two, right? View image: IMG 0048
Can I check them while they are soldered to the board or i have to take them off?
Can I check them while they are soldered to the board or i have to take them off?
The op-amps that you need to check are all of the 8-pin inline ICs like the ones near the fixative you removed. The output pins are 1 and 7.
ok! Sorry for another noob question, but in order to do this reading, the amp should be turned on? Becouse with the amp off, dmm set to dc, black probe on GND, all the output pins are almost 0v
Thanks again for the assistance!
Thanks again for the assistance!
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