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Old 23rd February 2012, 05:47 PM   #21
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Right-o. The preamp is on the LM3886 board...

However, I believe I found the solution. It may have been a combination of a few things...though I'm uncertain as to why they would all suddenly go wrong.

Anyway- I pulled out the Texas Instruments NE5532 op-amp that was on the faulty channel, as the amp was working...just there wasn't much power behind it. I just happened to have an prehistoric Signetics NE5532 in my parts bin so I put that one in. It was socketed.

And what do you know...it's back to normal. However, funny thing is that I also had to replace the pot because it was very very noisy and scratchy. Just plain weird. I was loosing my mind so I just put in an old Bourns one that I had and I knew how to wire. Sounds great now.

Still confused about the fuse blowing extravaganza, but for now, I'm going to accredit that to inrush current. Perhaps I should get some larger value fuses, maybe 5A+.

I still am uncertain as to why the op-amp suddenly stopped working though I guess I should just forget about it now.
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Old 23rd February 2012, 06:34 PM   #22
GloBug is offline GloBug  Canada
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Sounds like you have a handle on it now. My bread board amp started up dozens of times with a 3 amp fast blo, although I knew I needed a bigger one. (4~5amp)

As far as the rest just sounds like cheesy or fake parts. Its nice to have a junk pile to salvage parts from.
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Old 23rd February 2012, 06:38 PM   #23
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I doubt they were fake. I got them from Mouser. Who knows. As long as it doesn't happen again. Fingers crossed. Knock on wood.

My phone still won't play it, but I think that's just my phone...I think.
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Old 23rd February 2012, 06:40 PM   #24
GloBug is offline GloBug  Canada
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Oh sorry I though you mentioned you had a juanyang kit or something.
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Old 23rd February 2012, 09:30 PM   #25
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Quote:
Originally Posted by GloBug View Post
Oh sorry I though you mentioned you had a juanyang kit or something.
I did. My mistake. I just got the board. No parts. Yeah I'm confused as to why the op-amp died, but I won't question it further. I've been testing it and it seems fine.

Thanks for all the help/interest.
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Old 24th February 2012, 12:09 AM   #26
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I am glad you solved the problem!, now enjoy your diy amp
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Old 16th July 2012, 06:18 PM   #27
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I have a question, when i have not connect any input on my lm3886 amp (stereo) i'm getting 25V at the output and when i connect to the input an audio source i'm getting around 25mV
This is normal?
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Old 16th July 2012, 06:44 PM   #28
bcmbob is online now bcmbob  United States
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Which LM3886 design are you using?
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Old 17th July 2012, 07:39 AM   #29
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Quote:
Originally Posted by bcmbob View Post
Which LM3886 design are you using?
The circuit in datasheet
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Old 17th July 2012, 09:09 AM   #30
bcmbob is online now bcmbob  United States
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I'm not an expert in such things, but I've built four different LM3886 based amp designs and the process is always the same. I use a dim bulb tester at first power-up to determine if there are any shorts or transformer problems. Next is reading DC offsets and if the result is higher than a few mV, I stop there before attaching either a source or speakers. Full volt readings would push me to search for a serious problem.

I would suggest you post your situation to other threads where there is lots of activity - such as - Bought a XY LM3886 Kit.

Good luck..
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