My LM386N-1 just melted!Smoke everywhere!Can't breathe!HELP!

[ED]

Now this is DEFINETLY NOT my day. I have been working on my ruby amp, which i have had some problems with. Just earlier today i blew up an LED i was planning to use for a power indicator. But this takes the cake.

5 minutes ago i was trying my amp fully finished(2 fetzer valves as preamp as well as a buffer), and i was just biasing the 2nd fetzer stage. when this cloud of smoke started pouring out of my 386. it was unbelievable how much smoke was coming out of it. I stood there amazed and confused for about 5 seconds before the chip went bright orange. That's when i dived on the power switch. I stumbled out of my room finding it hard to breathe(burnt plastic is the worst smell) with a smoke cloud hovering above my bed.  

Is this where 'The Smokey Amp' got it's name?:lol:

I really want to get this thing working. Luckily i have a spare chip(i was gunna eventually convert it to a little gem MK2....). I was just running 12 volts DC at 2A from an adapter into it. Is this too much? It doesnt make much sense to me, as it was running ok before at 12volts before i put the 2nd fetzer into the circuit.  

Anyone got any helpful ideas/comments? Maybe i should give up.

[Travis]

Heat sink?  I found a few 25mm fans, and those coupled with a heatsink seem to keep my 386's just within the max limits.

LM386n-1 is rated at 12V max, as I recall.  Try a LM386-3 or a JRC/NJM386D.  I believe that both are rated at 18V. (All are rated at 150C)

I've burned a few 386's out, but I've never actually melted one.  You must be playing with some powerful mojo.

edit
Wow, I just saw the 12V@2A adapter.  You should measure that to see what it's putting out.  I bet it's much closer to 16-18V than to 12V.

[spongebob]

A LM386-3 is better for higher voltages, but they are so damn hard to find...

Before you replace the IC, make sure your wiring is correct, you didn't accidently short the output of the chip?

[Mark Hammer]

If the supply was able to deliver 2A to the chip at 12v and the chip had no current-limiting, then I would expect that anything less than an 8 ohm load would likely produce the "interesting effect" you observed.

This is really a case of "Be careful what you ask for because you might just get it".  If the supply voltage and the load result in greater current demand than the chip can handle, then don't be surprised if the chip self-destructs.

I'm not the mathematician here, but it bears noting that wattage is a function of the current, the supply voltage, and the load.  When a device is rated for XXX milli/watts, that does not mean ONLY how much power it can deliver, it also means how much ciurrent it can tolerate passing through its teeny transistors before heat overrules the entire process.

Heat sinking can help up to a point (8-pin dips aren't exactly made for massive heatsinks), but one needs to be attentive to the load used at the supply voltage used.  The material I've seen recommends use of higher-impedance loads at higher supply voltages, so as not to draw excessive current.

If you have a means of limiting the current supplied to the chip, that can also increase the likelihood that it won't take on current requests it can't handle.

Those who want more than headphone listening levels should probably consider opting for a 386-4 or another chip altogether.

On a related topic, I'm hoping to put some of the finishing touches on a small 2W practice amp circuit tonight, that uses a 380.  The 380 is a 14-pin DIP that has at least 6 of its pins (3 on each side) going to ground.  Most projects you'll see posted/published generally have board layouts with a LOT of copper devoted to ground immediately adjacent to the chip.  This is used partially for a heatsink, but there is a need for additional heat-sinking to keep a reasonable temperature on this puppy if one wishes to extract maximum output from it.

What I planned on doing (since the layout physically permits it)  is to bend a piece of aluminum into a tall, slender (width of the chip) U.  The ends are then filed downa bit, some conductive paste applied to the top of the chip, and the heat sink held in place by a piece of solid core wire "strapping" it to the top of the chip and soldered to the copper ground plane underneath.

I suppose something sort of like this is feasible for a 386 but you'd need to plan your layout accordingly.

[ED]

Your little amp sounds tops! Your own design? Post the schematic when your finished please!!!!!!!!!!!!!

[sir_modulus]

HOLY crap!!!! You pulled a me. I put some To-92 chips where I needed some To-3 ones and blew them up!!! Seriously though, I read the specs on the N-1 version! No wonder it blew.

Low Voltage audio amp.250m/6V 8 Pins

No.1
its rated for 250ma and 6V (a 12V @ 2A Wallwart will give you like maybe 30V (which is 5 times the max voltage)).

No.2
You don't need a heatsink/fan combo for a small thing like this. If it's being used intensivley, just use a piece of small metal wrapped around it and attached to the casing as a heatsink. NO FANS!

No.3
Get the N-3 version. Where do ya live? If in America or Canada, order the 12V version at abra electronics, (they have a montreal shipping centre). Shipping in Canada is like $10, so get some boxes or pots as well (the LM386 12V there is like 50 cents). Or if you live in america, get it from small bear electronics . Here is is 80 cents.

No.4
get a regulated PS. 30V is going to kill most chips. Get a 9VDC at 1amp PS. Then put it through a LM317T(available at Small bear) to keep it at 9VDC (email me if you need directions on this)

[ED]

Thanks for the advice everyone! Hahaha chips are funny.

Sir modulus,I live in Australia, so I get all my components from Jaycar Electronics. It's an excellent store in my opinion, cept i wish they had i slightly bigger range of chips. They only supply the LM386N-1, and not all the others that sound like they perform heaps better(my ruby does NOT have sparkly clean tones, but i still love it) and maybe even can tolerate my adapter!

I'd probably have to order overseas to get some 386Ds and 3s wouldnt I?

I'm a big fan of mini amps like this. Anyone got any other designs i can have a dig at(Preferbly simple!)?

Before i built this little ripper i played my strat without an amp or acoustically. I have a Peavey Rage 158 but in my opinion they totally suck. I'm building a tube amp soon(Marshall Plexi 50watt), so then i'll be in real buisness!

[Mark Hammer]

My "bench amp" is a little tyke with a 3" speaker made from an 8-pin NJM2073 chip pulled from a cheap pair of cast-off computer speakers.  The NJM2073 can run off supplies from 1.8 to 15V in either stereo or bridged mono mode.  The $10 speakers generally use them in stereo mode, which yields about a half watt per channel.  In bridged mode it packs quite a wallop; up to about 2W.  Best of all, quiescent current is very low so I find I can run it for a long time off a 9v battery.  It also requires very few external components for a functioning amp.  I used the datasheet circuit (3 caps and an RC Zobel network....that's it).  If you can't get 386-4's, I highly recommend this chip as a very nice replacement.  The TBA820 is also a very nice chip, delivering 1.2W ito 8R at 9vdc.  You can imagine that both of these chips cry out for an 8-pack of AA batteries.  You can't get 1.2W from a 9v battery for very long.

[Travis]

Winnipeg, eh?  I think that might explain why I need a fan and you don't.  I currently reside in the unacceptably hot, unacceptably flat lands of Houston, TX.  Never have so many been so proud of so little.

As it stands, even a six inch guitar speaker can push the LM386N-1 way to hard @ 12V here.  They die a fast death at the absolute max of 15V.  Even my  JRC386D's need some help in this place.  I can get by without the fan when I travel back to the Northeast.

[sir_modulus]

Yes i live in winterpeg(freezing during the winter, and lke 35 - 40 C in the summer) You can always go for a different design, as come on, A N-1 can barely ahndle any input, therefore it's ouput will be real low too. Try some other Amp IC's I'll list here. P.S. Yes overseas shipping would be needed, but at Small bear shipping a LM386 N-3 to australia is like $4.00 + 80Cents ( all $US). It's not too bad. Some other Amp Ic's:

(Man this Nat. Semiconductor book is awsome I was $2 at a garage sale)

LM's

LM386 N-1 = REally crap
LM386 N-3 = 1/2 to 1 Watt
LM390 = 1 Watt Bat. Operated Amp
LM388 = 1.5 Watts
LM380 = 2.5 Watts
LM377 = 2 x 2 Watts
LM384 = 5 Watts
LM383 = 7 Watts
LM378 = 2 x 4 Watts
LM12L = 150 Watts

Tda's (look elsewhere for these, there a bunch more)

TDA2002
TDA2003

[Hal]

i know they dont have any 386's, but you might be able to score some audio power amps as samples from TI.

They're really easy to get samples from.  You might need to pay shipping or duties or soemthing for international shipping, but still...

make sure u get the DIP package.  They're written weird...