Hi
I'm sure this will be amusing to some old hands but could really use a little guidance.
I decided to build a little power amp from an eBay kit to learn the basics before trying something more exotic. I went for an lm3886 kit.
The kit I bought actually came assembled much to my surprise and disappointment. However I thought it would be OK as a test....things went further downhill however as there were no instructions (they did take the time to send a nice keyring so that was nice🙂
I found some instructions that seemed very similar to mine so I went ahead and tried to get it working.
I used a transformer from a broken Arcam amp, should be 25v so seemed compatible.
There were no indicators on the pcbs so I'm sure the issue is either wiring the wrong way round or something not connected.
Anyway getting to the fireworks I plugged it in and upon pressing the on the switch the right hand chip actually caught fire!! I wasn't convinced it would word but didn't expect that.
The fuse in the socket didn't blow which I would have assumed would have.
I've added some pics, any comments welcome, I'm well aware I should have probably contacted the supplier to know what was what but I took the gamble and lost.
Certainly memorable and no one got hurt, potentially the dog heard some bad words but I did find out I'm not a natural electronics genius!
I'm sure this will be amusing to some old hands but could really use a little guidance.
I decided to build a little power amp from an eBay kit to learn the basics before trying something more exotic. I went for an lm3886 kit.
The kit I bought actually came assembled much to my surprise and disappointment. However I thought it would be OK as a test....things went further downhill however as there were no instructions (they did take the time to send a nice keyring so that was nice🙂
I found some instructions that seemed very similar to mine so I went ahead and tried to get it working.
I used a transformer from a broken Arcam amp, should be 25v so seemed compatible.
There were no indicators on the pcbs so I'm sure the issue is either wiring the wrong way round or something not connected.
Anyway getting to the fireworks I plugged it in and upon pressing the on the switch the right hand chip actually caught fire!! I wasn't convinced it would word but didn't expect that.
The fuse in the socket didn't blow which I would have assumed would have.
I've added some pics, any comments welcome, I'm well aware I should have probably contacted the supplier to know what was what but I took the gamble and lost.
Certainly memorable and no one got hurt, potentially the dog heard some bad words but I did find out I'm not a natural electronics genius!
Attachments
Hard to tell much from those pics, but +ve and -ve rails the wrong way round would certainly kill it. Now you know why all the guides recommend that, for first power up you use an incandescent bulb in series with the mains.
Hi,
From what I can see you have messed up the speaker
connections. If you buy a board and leave one one of
its connections unconnected you'd better know why.
rgds, sreten.
From what I can see you have messed up the speaker
connections. If you buy a board and leave one one of
its connections unconnected you'd better know why.
rgds, sreten.
Yeah, the bulging bypass cap on one of the boards would tend to indicate that the supply rails were connected backwards.
Another possibility is that you exceeded the rated voltage of the chip and parts on the board.
Get an inexpensive DMM, order another set of boards, build yourself what unfortunately has come to be known around here as the "dim bulb tester" aka ballast lamp, etc., and try again.
I use similar boards in some of my motor drives and have generally had to modify them for stability, but this looks like operator error to me.
I would actually recommend reading up on the LM3886 amplifier at the Neurochrome website, note that some LM3886 kits can also be found there, and unlike the eBay crapshoot these if built according to directions will definitely work: Neurochrome Audio: High performance DIY audio circuits.
Tom is quite active here.
Another possibility is that you exceeded the rated voltage of the chip and parts on the board.
Get an inexpensive DMM, order another set of boards, build yourself what unfortunately has come to be known around here as the "dim bulb tester" aka ballast lamp, etc., and try again.
I use similar boards in some of my motor drives and have generally had to modify them for stability, but this looks like operator error to me.
I would actually recommend reading up on the LM3886 amplifier at the Neurochrome website, note that some LM3886 kits can also be found there, and unlike the eBay crapshoot these if built according to directions will definitely work: Neurochrome Audio: High performance DIY audio circuits.
Tom is quite active here.
I remember my first build, a Maplin 50 watt amp in 1980.
The heat sink and pcb were out of stock so I built it up without just rats nesting it.
Of course it put out the magic smoke on power up.
I learned patience and taking more care from that first experience.
You were lucky just to get a small fire, if the electrolytics were powered backwards they have a tendency to explode.
The heat sink and pcb were out of stock so I built it up without just rats nesting it.
Of course it put out the magic smoke on power up.
I learned patience and taking more care from that first experience.
You were lucky just to get a small fire, if the electrolytics were powered backwards they have a tendency to explode.
Messing up with the rail connections has a tendency to let the magic smoke out.
Been there, done that. Cost me €100+postage....
Johan-Kr
Been there, done that. Cost me €100+postage....
Johan-Kr
Looks like this one.
https://www.yuan-jing.com/stereo/lm3886-power-regulator-board-68w-68w
Not that identifying it revealed any great store of info or even more and larger piccies.
J.
https://www.yuan-jing.com/stereo/lm3886-power-regulator-board-68w-68w
Not that identifying it revealed any great store of info or even more and larger piccies.
J.
I couldn't agree more with Kevin's suggestion. Even Tom's modest LM3886DR is an excellent sounding piece. That's DR for "done right" - having heard both that model and the Modulus I can attest they sound better (should say they don't "sound" at all) than any other DIY / kit chip amp I've heard.
If the board in question was from Yuan-Jing, and you've already tried contacting them for after sales service, I think you'll find you got what you paid for. I had that experience with one of their pre-built amps- the tone control got locked up with full bass at the first test run, and it took almost a month to get a replacement control to reset it to stock. The remote has since been decommissioned.
If the board in question was from Yuan-Jing, and you've already tried contacting them for after sales service, I think you'll find you got what you paid for. I had that experience with one of their pre-built amps- the tone control got locked up with full bass at the first test run, and it took almost a month to get a replacement control to reset it to stock. The remote has since been decommissioned.
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