Blew an LM4780 chip last night!How?

Dominick22 · 13th January 2006, 03:22 PM

So last night, I was fooling around with my completed mono amps trying different speakers. I actually had the cd input signal on pause when there where a few bright flashes.

When I looked closely, The 1, 3, and possibly 2 pins were fried!

So any ideas as to what caused it?
I have used the amp for about 5 hours (easy listening) intermittently so far before this happened and the other mono amp is fine, although it is wired the same way???

Thanks,
Dominick in New Jersey

peranders · 13th January 2006, 03:30 PM

What did the "fooling" consist of really? How does the amp and the wiring look like? Some short, loose wire etc?

A LM4780 doesn't pop just like that.

Dominick22 · 13th January 2006, 03:35 PM

Well, I decided to try them on my Martin Logan Clarity's and listened for 1 song, about 3 minutes and then hit pause on the cd player. About 1 minute later, while on pause still, Bada Boom Bada Bing! An indoor lightning show!LOL

I am really clueless. Is it possible that there was a delayed failure reaction??

Dominick

Narcisse91 · 13th January 2006, 03:40 PM

Are any other components damaged?

peranders · 13th January 2006, 03:43 PM

Did your amp had any output filter? Martin Logan's are a bit capacitive by nature.

Does your amp have any input filter? Maybe HF garbage went through?

Dominick22 · 13th January 2006, 04:48 PM

The compenents were put together exactly the way they come from audiosector.com!

I did not add any caps or anything else.

So did the ML's burn it?

Dominick

Dominick22 · 13th January 2006, 04:51 PM

From what I can SEE, nothing else was damaged.

tiltedhalo · 13th January 2006, 05:23 PM

The ML are a very inductive load, the impeadence at high frequencys can drop as low as .5ohms!!! Chip are prone to high frequency oscillations also. You should always use an input coupling cap with parelleled solutions, also an input network 1k and 22k to ground to set input gain, you need a Ci cap or servo.

Bazukaz · 13th January 2006, 07:47 PM

It isn't easy to burn these chips , even with hard capacitive/inductive loads.Check power supply , rectifiers , insulation to heat sink.

Dominick22 · 15th January 2006, 11:57 AM

My heatsink for the chip was touching the mounting plate for the 330 va transformer...but the mounting plate is isolated and it doesn't make actuall contact with the transformer itslef.

Could this be the cause? I wouldn't think so.

Dominick

13th January 2006, 03:22 PM	#1
Dominick22 diyAudio Member Join Date: Aug 2005	Blew an LM4780 chip last night!How? So last night, I was fooling around with my completed mono amps trying different speakers. I actually had the cd input signal on pause when there where a few bright flashes. When I looked closely, The 1, 3, and possibly 2 pins were fried! So any ideas as to what caused it? I have used the amp for about 5 hours (easy listening) intermittently so far before this happened and the other mono amp is fine, although it is wired the same way??? Thanks, Dominick in New Jersey __________________ A real amateur enthusiast!

13th January 2006, 03:30 PM	#2
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	What did the "fooling" consist of really? How does the amp and the wiring look like? Some short, loose wire etc? A LM4780 doesn't pop just like that. __________________ /Per-Anders (my first name) or P-A as my friends call me

13th January 2006, 03:35 PM	#3
Dominick22 diyAudio Member Join Date: Aug 2005	Well, I decided to try them on my Martin Logan Clarity's and listened for 1 song, about 3 minutes and then hit pause on the cd player. About 1 minute later, while on pause still, Bada Boom Bada Bing! An indoor lightning show!LOL I am really clueless. Is it possible that there was a delayed failure reaction?? Dominick __________________ A real amateur enthusiast!

13th January 2006, 03:43 PM	#5
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Did your amp had any output filter? Martin Logan's are a bit capacitive by nature. Does your amp have any input filter? Maybe HF garbage went through? __________________ /Per-Anders (my first name) or P-A as my friends call me

13th January 2006, 04:48 PM	#6
Dominick22 diyAudio Member Join Date: Aug 2005	The compenents were put together exactly the way they come from audiosector.com! I did not add any caps or anything else. So did the ML's burn it? Dominick __________________ A real amateur enthusiast!


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13th January 2006, 03:40 PM	#4
Narcisse91 diyAudio Member Join Date: Aug 2002 Location: NY	Are any other components damaged?

13th January 2006, 04:51 PM	#7
Dominick22 diyAudio Member Join Date: Aug 2005	From what I can SEE, nothing else was damaged. __________________ A real amateur enthusiast!

13th January 2006, 05:23 PM	#8
tiltedhalo diyAudio Member Join Date: Sep 2005 Location: Melbourne Florida	LM4780 The ML are a very inductive load, the impeadence at high frequencys can drop as low as .5ohms!!! Chip are prone to high frequency oscillations also. You should always use an input coupling cap with parelleled solutions, also an input network 1k and 22k to ground to set input gain, you need a Ci cap or servo.

13th January 2006, 07:47 PM	#9
Bazukaz diyAudio Member Join Date: Nov 2005 Location: Vilnius	It isn't easy to burn these chips , even with hard capacitive/inductive loads.Check power supply , rectifiers , insulation to heat sink.

15th January 2006, 11:57 AM	#10
Dominick22 diyAudio Member Join Date: Aug 2005	My heatsink for the chip was touching the mounting plate for the 330 va transformer...but the mounting plate is isolated and it doesn't make actuall contact with the transformer itslef. Could this be the cause? I wouldn't think so. Dominick __________________ A real amateur enthusiast!

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