Fake LM3886T ???? - Page 2

timpert · 11th June 2008, 06:38 PM

Do you have any intact samples of this device? If you measure a diode to substrate (V-) or to V+ (easily checked with a multimeter) on an NC pin, then the fake hypothesis gets stronger again...

poynton · 11th June 2008, 07:02 PM

Quote:

Originally posted by timpert
Hi,

A little more searching yielded this thread:

Picture of a fake LM3886

I can't get this to work.
Anyone else have problems ?

Andy

SpittinLLama · 11th June 2008, 07:54 PM

They may also be remarked. The LM4700 is rotated like that. The LM3886 & LM3876 should have double bond wires to the ouptut, Vcc and Vee pins. If single wire it is absolutely not a LM3886 or LM3876. The LM4700 also has a Standby pin so see if there are wires there. If you can get a scope you might be able to read the name on the die. This will tell you what it is but this can also be faked.

It would be quite a big mistake to assemble parts wrong. And these parts are tested after assembly unlike some super small ICs where test is limited to wafer form only. Possible National made an error but more likely there is something 'funny' with these parts.

-SL

Netlist · 11th June 2008, 07:59 PM

Andy, that server must be down.

/Hugo

robertj88 · 11th June 2008, 09:58 PM

Last week I cracked a couple of LM3886T's and LM3886TF's, witch absolute can't be fake. Since then I had a new key-ring

It was exactly the same as yours, same die on an same "strange" angle. So I really think the chips are the "original" National ones.

Success with youre amp!

Robert

SpittinLLama · 11th June 2008, 10:12 PM

hmmm, I will double verify my info and get back to this thread.

-SL

SpittinLLama · 11th June 2008, 11:57 PM

Well maybe it changed some time but Robertj88 is right, the LM3886 is rotated just a little counter clockwise, just like your picture. The die ID should be at the bottom towards the right to look at if you have a microscope. So it is looking more like you do not have fakes, might want to spend time double checking circuit.

Sorry for the confusion earlier about rotation.

-SL

thoronx · 12th June 2008, 07:30 AM

1. PSU (Suspected!)
The unregulated PSU was built based on carlosfm's psu design with small exception, I have used two rectifier bridges instead of one, the transformer is about 400VA, with center tapped secondary (3 wires), after I have assembled the psu, I mesured the voltages on the output without the amp connected,and without any load, it was nearly +-30V, far in the safe operation area of the LM3886.

thoronx · 12th June 2008, 07:33 AM

2. AMP
I choosed to build my amp based on the Elector 1998/7-8 publication, the PCB was made by me using toner-transfer method

thoronx · 12th June 2008, 07:34 AM

The PSU PCB,

12th June 2008, 07:30 AM	#18
thoronx diyAudio Member Join Date: May 2007	1. Psu 1. PSU (Suspected!) The unregulated PSU was built based on carlosfm's psu design with small exception, I have used two rectifier bridges instead of one, the transformer is about 400VA, with center tapped secondary (3 wires), after I have assembled the psu, I mesured the voltages on the output without the amp connected,and without any load, it was nearly +-30V, far in the safe operation area of the LM3886.

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11th June 2008, 06:38 PM	#11
timpert diyAudio Member Join Date: Nov 2004 Location: Netherlands	Do you have any intact samples of this device? If you measure a diode to substrate (V-) or to V+ (easily checked with a multimeter) on an NC pin, then the fake hypothesis gets stronger again...

11th June 2008, 07:54 PM	#13
SpittinLLama diyAudio Member Join Date: Apr 2005 Location: In the Wild, Wild West	They may also be remarked. The LM4700 is rotated like that. The LM3886 & LM3876 should have double bond wires to the ouptut, Vcc and Vee pins. If single wire it is absolutely not a LM3886 or LM3876. The LM4700 also has a Standby pin so see if there are wires there. If you can get a scope you might be able to read the name on the die. This will tell you what it is but this can also be faked. It would be quite a big mistake to assemble parts wrong. And these parts are tested after assembly unlike some super small ICs where test is limited to wafer form only. Possible National made an error but more likely there is something 'funny' with these parts. -SL

11th June 2008, 07:59 PM	#14
Netlist diyAudio Moderator Join Date: Jan 2003	Andy, that server must be down. /Hugo

11th June 2008, 09:58 PM	#15
robertj88 diyAudio Member Join Date: May 2007	Last week I cracked a couple of LM3886T's and LM3886TF's, witch absolute can't be fake. Since then I had a new key-ring It was exactly the same as yours, same die on an same "strange" angle. So I really think the chips are the "original" National ones. Success with youre amp! Robert

11th June 2008, 10:12 PM	#16
SpittinLLama diyAudio Member Join Date: Apr 2005 Location: In the Wild, Wild West	hmmm, I will double verify my info and get back to this thread. -SL

11th June 2008, 11:57 PM	#17
SpittinLLama diyAudio Member Join Date: Apr 2005 Location: In the Wild, Wild West	Well maybe it changed some time but Robertj88 is right, the LM3886 is rotated just a little counter clockwise, just like your picture. The die ID should be at the bottom towards the right to look at if you have a microscope. So it is looking more like you do not have fakes, might want to spend time double checking circuit. Sorry for the confusion earlier about rotation. -SL

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