Picture of a Fake LM3886 (not sure yet, but probabily it is!) - diyAudio
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Old 2nd June 2006, 02:13 AM   #1
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Exclamation Picture of a Fake LM3886 (not sure yet, but probabily it is!)

Hi !

I built a stereo amp with two 3886s, they were running with 33+33V each one with a 8Ohms Load (JBL E60).

They used to heat quickly, but it never burned... Supply just used to get warm.


Yesterday, I was very very tired, then I decided to listen some Quincy Jones, so I was connecting the amp to the supply and made a big mistake. The GND was connected to -VS and -VS to GND. Crash'n Boom hehehe, just one second (I heard HUMMMMMMMMMMM) and the amp was DEAD.


Hooooly Shiii...


Okay, very HAPPY I left all things in my living room and went to my bed to sleep.

Today in the morning, I ordered some 3886s from FARNELL, and they arrived four hours after I ordered it !

I fixed the amp and wheeeen I putted it to work... WHAT WAS THAT SOUND !?


Muuuchhh more LIVE, SPACED and the bass was much more tight ! The treble was much more focused and I could feel every instrument much more far from each other!

The woofer was moving much more less and producing a BETTER sound, and it was just WARM and not HOT like it used to be.


Anyway, I think it's strange a fake IC last all that time !


Here is some pictures, I'll be glad if you give me some feedback, saying if it is fake or not.


http://files.upl.silentwhisper.net/u...Photo-0041.jpg
http://files.upl.silentwhisper.net/u...Photo-0043.jpg


Thank you !!!
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Old 2nd June 2006, 02:44 AM   #2
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The code is:

JM14BP
LM3886T


http://www.national.com/quality/mark...nventions.html

There's no "BP" here, or I'm blind?


And If you see the die, it isn't properly aligned.


Really fake?
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Old 2nd June 2006, 09:14 AM   #3
Wynand is offline Wynand  South Africa
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Where did you get the "fake" chips from?
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Old 2nd June 2006, 09:17 AM   #4
ilimzn is offline ilimzn  Croatia
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It is difficult to say wether it is genuine or fake since you have busted it open before taking a photo of the whole case. As for the die, I am not sure how it is attached in the LM3886 (I could crack open one of my genuine ones, but I think I'll rather keep it in one piece ), but it is not so uncommon to attach a die sideways if it makes it easyer to wire to the pin frame.
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Old 2nd June 2006, 04:30 PM   #5
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I got them from a small store on the city. Here's the Fake Town, if you ask for 2N3055 from toshiba, everybody will have it !


Then I ordered some from farnell !


I have more two burned ICs, I'll open them. If they're just like the "fake", I'll open a genuine from farnell !

Better loose some money and know what I'm putting on the boards!
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Old 2nd June 2006, 07:19 PM   #6
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YES, they are fake !

There was no diference in the package, I placed the fake side by side with the original, and you can't see any diference.


I opened an 3886TF genuine, and I found what I was expecting. The genuine is better built and have the core perfectly aligned.

Some pictures again !

http://files.upl.silentwhisper.net/u...Photo-0047.jpg
http://files.upl.silentwhisper.net/u...Photo-0049.jpg

edit:

The most interesting is, it don't sound that bad ! Of course the genuine sounds MUCH better, but to a fake, isn't that bad ! hahahah

I used a lot the fakes, no problem heheh ! Used them with 33+33v @ 8Ohms, they were not noisy and I had no problems with them. I replaced them just because I did a mistake with the supply !

The fakes really surpassed my expectations!

Anyway, the genuine improved everything, since how tight is the bass now, till the amp efficience.


Be careful, anyone here can be using fakes without know !
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Old 2nd June 2006, 07:50 PM   #7
Bazukaz is offline Bazukaz  Lithuania
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Hi ,
I think that it is not necessary to dissasemble ICs to determine if they are fakes. Try to push the IC hard at low drive impedance(like 2 ohms).
If it blows , or there is no spike response(high frequency "clicking") , it is probably fake.
Maybe these can be renamed cheaper ICs , like ones from ST(TDAs) ?
I can't believe they could build a factory to manufacure fake chips...

Regards,
Lukas.
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Old 16th March 2011, 09:51 PM   #8
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Sorry for grave digging but I thought the following info may be useful to people buying 3886s.

The first line should be a manufacturing code and the second line either 'LM3886T' or 'LM3886TM'. There should be nothing else marked. I've seen a chip marked 'LM3886TM +P' but can't find a reference to that extra +P in any National Semi documentation.

The device code should be the National Semi logo followed by 6 digits: die factory code (1 letter); assembly factory code (1 letter); date code (2 digits); die run code (2 letters).

eg: PM41AV means the silicone wafer was made in China in a batch designated 'AV', the body in Malaysia in 2004. JM88AP means the wafer was made in Japan in a batch designated 'AP' and the body in Malaysia in 2008.

Date and factory codes: http://www.national.com/analog/quali...ng_conventions

There are a lot of cheap 3886s on eBay with photos showing a 4 digit code - that's not a standard code!

It seems likely to me, or at least quite possible, that fake LM3886xx chips are actually LM3875xx re-marked as they have the same TA11B/TF11B packages. 3875 chips have no mute function which may be a good test method.

NB: All insulated TF11B packages, for some reason, have fractionally narrower legs than the uninsulated version.

NB: Both bold white screen printed and fine yellowish laser etched markings are valid. National moved from the former to later process so the most recently made chips will be laser etched.
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Old 19th March 2011, 10:19 PM   #9
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Quote:
Originally Posted by random007 View Post
Sorry for grave digging but I thought the following info may be useful to people buying 3886s.

The first line should be a manufacturing code and the second line either 'LM3886T' or 'LM3886TM'. There should be nothing else marked. I've seen a chip marked 'LM3886TM +P' but can't find a reference to that extra +P in any National Semi documentation. ...
The +P sounds like a select part; if so it won't be in the regular documentation since it would be part of an OEM order or specification.
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Old 20th March 2011, 09:12 AM   #10
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What makes you think that someone who is able to fake ICs would be unable to copy a correct looking manufacturing code?
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