Hello everybody
I have been building with chip-amps for some time now, mostly the NSC LM3xxx-series. From time to time I have "killed" the chip, (despite all the fancy protection they include.....).
However I have NEVER expirenced a huge DC-voltage on the output of the chip after I "killed" it. A big (LS-destructive) DC-voltage on the output is normally what you see on a "killed" discrete power amp, since the output tense to sving to one of the rails.
I do have some idear about why you don't see that on chip-amps, but I very much like to hear from other people who have "killed" a chip-amp or two alone the way.
Are your expirence the same as mine or have I just been lucky ??
Thomas
I have been building with chip-amps for some time now, mostly the NSC LM3xxx-series. From time to time I have "killed" the chip, (despite all the fancy protection they include.....).
However I have NEVER expirenced a huge DC-voltage on the output of the chip after I "killed" it. A big (LS-destructive) DC-voltage on the output is normally what you see on a "killed" discrete power amp, since the output tense to sving to one of the rails.
I do have some idear about why you don't see that on chip-amps, but I very much like to hear from other people who have "killed" a chip-amp or two alone the way.
Are your expirence the same as mine or have I just been lucky ??
Thomas
I've blown a STK4141ii chip and it applid the +70v voltage rail directly to the speaker . 
it wasn't very nice 🙂)
P.S. maybe there is a capacitor wich blocks the DC part of the output, or a fuse in the power supply...
it wasn't very nice 🙂)P.S. maybe there is a capacitor wich blocks the DC part of the output, or a fuse in the power supply...
)
the_DOOMer said:I've blown a STK4141ii chip and it applid the +70v voltage rail directly to the speaker .
aren't they thick-film hybrid amps? that would make them closer to discrete amps (op-amp front end + discrete OPS) than to true monolithic chips like the Overture.
and Ohms law is no fun.....
in such case usually You get sentenced to say "U" divided through "I" times (where "U" is the chip part number and "I" is reciprocal value of numbers of chips You killed) .....I must not kill chip amps.....I must not kill chip amps.....
go figure what this means for killing two 3875 Gainclone chips
tlmadsen said:
I think you will find that lead wires have fused, or tracks on the chip have fused.
Some smaller transistors fail open circuit, and most high power discrete output transistors fail short circuit, and fuses etc blow before the internal lead wires go open.
Eric.
I wired + and - wrongly on the whole circuit and both 3875 smoked. the caps and resistors survived. no voltage on output though....
Just as a sefety reminder, do use glasses whenever powering
up something you don't already know for sure is correctly
wired and working. These things can explode. A plain old
741 almost "shot" me in the eye once. I can't remember this
many years afterwards what I did wrong, but I might very well
have reversed the supplies. BTW, the 741 ended up with an
"inspection hole" so I could wiev the chip afterwards. 🙂
tlmadsen said:
I blew up a 3886, and I saw the negative voltage rail on the output. Luckily, it was not connected to anything at the time, so I did not damage anything.
Also, it blew because I tried to connect my PS before discharging my 10,000 uf caps, so it was my fault. I always checked the output with a meter for DC before connecting it to my speakers.
Randy
What happens? Well, you get really ****ed because it was your last chip and then you go buy more.
I just accidentally connected the + and - voltages backwards... It sucks...
I just accidentally connected the + and - voltages backwards... It sucks...
Yeah...My friend also did that once...put the caps in worng way round (the negative side) and got it blowing it out from him...hit his face with all the stuff inside...luckily didn't hit his eye...I was there when he did that...never bothered to check his cap soldering before power-up...
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