I think I killed it.

Nappylady · 9th November 2003, 03:29 AM

LM3875. Single chip amplifier. +/-38 volt rails, 1000 uF filters. I'm 99.9% sure I got everything right--nothing blew up, and my meter told me all was well.

Still, I hooked up a speaker and--+V rail appears at the output. Whoops.

Does this mean the chip is dead? Or do I just have something wired wrong? It's not a super big deal... it was an ugly hackjob anyway... but from what I'd read, the chips mostly didn't swing one way or the other when they died... This is my first attempt and I don't know if I should just move on or check my connections for a 43rd time...

Thanks all.

(PS - it actually made a pretty neat noise when I turned it on with a load connected... too bad it burned out the speaker in the process.

)

li_gangyi · 9th November 2003, 05:27 AM

check your other rail...might be disconnected or your input might be tied somewhere...where it's not suppossed to be~!!!

lieven · 9th November 2003, 06:28 AM

Been there, seen that....

Please explain first your setup to us (inverting igc or non-inverting nigc) + resistor and cap values.

antomas · 9th November 2003, 09:23 PM

Hi Nappylady,
+-38V seems to me a bit too close to the voltage limit of +-42V (datasheet page 3). Could this be the cause of your problem?
Ciao, Massimo

Matttcattt · 9th November 2003, 09:33 PM

this happened to me, with my OPA541 amp, turned out, i connected +v and -v the wrong way round on both amps, very confusing diagram (OPA541AM).

Stabist · 9th November 2003, 10:32 PM

Hi!

A friend of mine and I also killed one of the GC yesterday ...

Pitty ...

Still - one picture of the "protoype" that didn't survive the burning in ....

Stabist · 9th November 2003, 10:40 PM

But than again - it might be the destiny - 'cause now the chassis will be redesigned a bit ... And also the topology will be changed ...

Hush .. Still a bit sad because of poor LM's that got fried in an unfriendly maner

And another picture ...

jackinnj · 9th November 2003, 10:59 PM

GC's don't like to be sine-wave tested (although we don't know from your spec if this was what you were up to.)

Further, you really have to pay attention to the heat sink specs, hf oscillation etc. These big op-amps are not quite that simple to implement.

ronc · 9th November 2003, 11:13 PM

I love the smell of fried silicone in the morning.
ron

jackinnj · 9th November 2003, 11:55 PM

Quote:

Originally posted by ron clarke
I love the smell of fried silicone in the morning.
ron

I prefer bacon, resistors and coffee

9th November 2003, 03:29 AM	#1
Nappylady diyAudio Member Join Date: Feb 2003 Location: Salt Lake City	I think I killed it. LM3875. Single chip amplifier. +/-38 volt rails, 1000 uF filters. I'm 99.9% sure I got everything right--nothing blew up, and my meter told me all was well. Still, I hooked up a speaker and--+V rail appears at the output. Whoops. Does this mean the chip is dead? Or do I just have something wired wrong? It's not a super big deal... it was an ugly hackjob anyway... but from what I'd read, the chips mostly didn't swing one way or the other when they died... This is my first attempt and I don't know if I should just move on or check my connections for a 43rd time... Thanks all. (PS - it actually made a pretty neat noise when I turned it on with a load connected... too bad it burned out the speaker in the process. )

9th November 2003, 05:27 AM	#2
li_gangyi diyAudio Member Join Date: Jun 2003 Location: Woodlands Circle	check your other rail...might be disconnected or your input might be tied somewhere...where it's not suppossed to be~!!! __________________ Kids in the back seat cause accidents...Accidents in the back seat cause kids...

9th November 2003, 09:33 PM	#5
Matttcattt diyAudio Member Join Date: Feb 2003 Location: Bristol	this happened to me, with my OPA541 amp, turned out, i connected +v and -v the wrong way round on both amps, very confusing diagram (OPA541AM). __________________ If it aint broke, don't fix it. If it is broke, fix it. If you can't fix it, take it apart and see how it "worked".

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9th November 2003, 06:28 AM	#3
lieven diyAudio Member Join Date: Aug 2002 Location: Belgium	Been there, seen that.... Please explain first your setup to us (inverting igc or non-inverting nigc) + resistor and cap values.

9th November 2003, 09:23 PM	#4
antomas Maître sans marteau diyAudio Member Join Date: Feb 2003 Location: Torino, Italy	Hi Nappylady, +-38V seems to me a bit too close to the voltage limit of +-42V (datasheet page 3). Could this be the cause of your problem? Ciao, Massimo

9th November 2003, 10:59 PM	#8
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	GC's don't like to be sine-wave tested (although we don't know from your spec if this was what you were up to.) Further, you really have to pay attention to the heat sink specs, hf oscillation etc. These big op-amps are not quite that simple to implement.

9th November 2003, 11:13 PM	#9
ronc diyAudio Member Join Date: Mar 2003	I love the smell of fried silicone in the morning. ron

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