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Old 21st December 2012, 09:42 PM   #1
calgarc is offline calgarc  Canada
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Default lm386 over heating. please help

i have been soldering my 386 amp together... i seem to be sending power (9v) to the speaker (4ohm) just fine and it does work for the most part. but the chip over heats in seconds.

i checked and though maybe the power was soldered the wrong way. even with the +/- connections reversed i get the same problem.


the chip is running on 9v, with a 5k gain pot and 10k volume pot.

i am working on getting schematics of my exact circuit to put on here. does anybody know what might be goin wrong?? what information other then a schematic would you guys need
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Old 21st December 2012, 11:31 PM   #2
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Looking at the data sheet, it dissipates maybe half a watt of heat at 9V 4 ohms and 0.1 watt output. And the thermal resistance from j to ambient is well over 100 C/W

So I would expect the thing to get hot.

But it could be some hf instability that's doing it. Show schematic

Last edited by Robert Kesh; 21st December 2012 at 11:34 PM.
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Old 22nd December 2012, 12:36 AM   #3
gootee is offline gootee  United States
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Post a photo of the circuit.

Are you using a heatsink of any kind?
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Old 22nd December 2012, 12:57 AM   #4
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Quote:
Originally Posted by calgarc View Post

even with the +/- connections reversed i get the same problem.
If you have applied power the wrong way around you will most likely kill the chip.
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Old 22nd December 2012, 01:13 AM   #5
JMFahey is offline JMFahey  Argentina
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Did you use an output coupling cap?
Please post the actual schematic of what you built.
Do not copy and paste the application datasheet schematic, we already know that one works, please draw what *you* did, looking at it.
Thanks.
PS: maybe you mounted the chip the wrong way.
Maybe it's toast by now
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Old 22nd December 2012, 01:35 AM   #6
calgarc is offline calgarc  Canada
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yes i have 2 caps on the device. i am working on creating a schematic of what i built.. i get some noise from the speaker when i power it up, but no sound from the input. maybe i wired a cap in the wrong spot??

and about the chips, i have a pack of 386n-4 so i am not worried about destroying a chip lol
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Old 22nd December 2012, 01:48 AM   #7
calgarc is offline calgarc  Canada
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sorry for the massive imageClick the image to open in full size.
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Old 22nd December 2012, 02:04 AM   #8
calgarc is offline calgarc  Canada
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i resolved my heat issues now for the sound lol
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Old 22nd December 2012, 02:10 AM   #9
gootee is offline gootee  United States
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Is that the complete schematic? You don't show anything connected to the +V power-supply input pin (6).

Have you looked at the datasheet circuits? It is here:

http://www.ti.com/product/lm386

Last edited by gootee; 22nd December 2012 at 02:13 AM.
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Old 22nd December 2012, 02:32 AM   #10
calgarc is offline calgarc  Canada
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Quote:
Originally Posted by gootee View Post
Is that the complete schematic? You don't show anything connected to the +V power-supply input pin (6).

Have you looked at the datasheet circuits? It is here:

Speaker Amplifier and Modulator - Mid/High-Power Amplifier - LM386 - TI.com
DOH i forgot that. there is a switch between pins 6 and the + of the power
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