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-   -   LM3886T Problem, I think (http://www.diyaudio.com/forums/chip-amps/70559-lm3886t-problem-i-think.html)

Panelhead 28th December 2005 01:39 AM

LM3886T Problem, I think
 
I recently had a failure in an using a LM3886T chip. The amp about blew up my eardrums on one channel. It was a real loud buzz.
After disconnecting it I found almost the full positive rail voltage on the output. It was disasembled to check for problems, and nothing wrong was found. Check the chip and it was not shorted on either rail.
Powered back up, and the chip acted up a little and finally stabilized. It even amplifed. Operated fine for about an hour. But then started passing dc again.
This is not how I expected a LM3886 chip to fail. I always thought they either work, or they do not. This seems intermittant.
When I have time, I will clip it out and try to install another in the circuit board. Hopefully this problem will not still be there.
Have others seen these chips act up, settle down, and start acting up again?

George

odysseybmx414 28th December 2005 01:50 AM

do you have a loose solder somewhere or a connection touching something it shouldnt??

Jay 28th December 2005 03:08 AM

indeed you should check connections in your power supply

peranders 28th December 2005 06:16 AM

Since you were using the uninsulated "T" version, was the insulation 100%?

Panelhead 28th December 2005 10:07 AM

Good news
 
I have double checked all connections and the status of the mica insulator. But the come and go nature made me think that clipping out the LM3886T would only be a lot of work for nothing.
Guess I need to dig back into the circuit board again and see what has caused this. It acted up after playing one morning for a couple of hours. It had been sailing along for a couple months.
I was sitting about 10 feet away when the 32 vvolts hit that speaker. My ears rang for a day. My wife was downstairs and she thought something blew up. Lowther drivers are tougher than most think.

George

sagarverma 28th December 2005 10:08 AM

Quote:

It even amplifed. Operated fine for about an hour. But then started passing dc again.
check all the solder joints carefully.dry joints cause probs.


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