about LM675T

Richard.C · 19th August 2005, 04:03 AM

My LM675T's all 5 feet are derect, but its datasheet in NS web cite show that it is same to LM1875T in appearance,....Why?

wes-ninja250 · 19th August 2005, 04:58 AM

According to the national data sheets:

http://www.national.com/ds/LM/LM675.pdf
http://www.national.com/ds/LM/LM1875.pdf

the LM675T is in a NS TO5D case, where as the LM1875T is in an an NS package number TA05B case. These appear to be the same as far as the PCB is concerned, but the leads are "bent" 90 degrees on the 1875, making it more suitable to for a horizontal bolted-through-the-board heat sink, whereas the 675 looks like it'd be happier with the upright style, either bolted freely to the package (it doesn't look it'd much heatsinking), or to an off-PCB heatsink (e.g. chassis-mount).

Caveat: I know nothing of these two chips, other than what I read [quickly] in the data sheets.

Wes

Richard.C · 19th August 2005, 06:33 AM

but my 675's 5 leads are all in one plane! it's different with the NS datasheet, am i buy a fake?

wes-ninja250 · 19th August 2005, 01:16 PM

It's tough to say whether you're buying a fake or not, but I don't see National listing a part with straight legs. Is it stamped as a National Semiconductor part?

It is certainly possible that there are unlicensed Chinese clones floating around out there. There are a lot of very clever people over there, I remember years ago finding out that I had bought a batch 486DX2-66 chips which were actually 486DX2-50s, with the tops "planed" and re-stamped in China (came through an HK supplier). Boy was I upset, those chips were $660 each back then.

I would test the chip, and if it works, use it. Would you mind posting a photo?

Wes

wes-ninja250 · 20th August 2005, 01:49 AM

Hey, Richard -- I happened to stumble upon this link and thought you might find it interesting: http://sound.westhost.com/counterfeit.htm

Wes

Richard.C · 22nd August 2005, 01:49 AM

haha, it's interesting....
i have a picture of my lm675t chip, and a picture of the compare of 675 and 1875 ,but i don't kown how to upload them to this forum

Richard.C · 22nd August 2005, 02:19 AM

[IMG]675[/IMG]

Richard.C · 23rd August 2005, 02:38 AM

help me!
how to paste a picture in my post??

wes-ninja250 · 23rd August 2005, 04:11 AM

-----------

Richard.C · 24th August 2005, 03:26 AM

thank you, wes-ninja250!
please look the picture,

19th August 2005, 04:03 AM	#1
Richard.C diyAudio Member Join Date: Aug 2004 Location: China	about LM675T My LM675T's all 5 feet are derect, but its datasheet in NS web cite show that it is same to LM1875T in appearance,....Why?

19th August 2005, 06:33 AM	#3
Richard.C diyAudio Member Join Date: Aug 2004 Location: China	but ... but my 675's 5 leads are all in one plane! it's different with the NS datasheet, am i buy a fake?

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19th August 2005, 04:58 AM	#2
wes-ninja250 diyAudio Member Join Date: Feb 2005 Location: Kingston, ON	According to the national data sheets: http://www.national.com/ds/LM/LM675.pdf http://www.national.com/ds/LM/LM1875.pdf the LM675T is in a NS TO5D case, where as the LM1875T is in an an NS package number TA05B case. These appear to be the same as far as the PCB is concerned, but the leads are "bent" 90 degrees on the 1875, making it more suitable to for a horizontal bolted-through-the-board heat sink, whereas the 675 looks like it'd be happier with the upright style, either bolted freely to the package (it doesn't look it'd much heatsinking), or to an off-PCB heatsink (e.g. chassis-mount). Caveat: I know nothing of these two chips, other than what I read [quickly] in the data sheets. Wes

19th August 2005, 01:16 PM	#4
wes-ninja250 diyAudio Member Join Date: Feb 2005 Location: Kingston, ON	It's tough to say whether you're buying a fake or not, but I don't see National listing a part with straight legs. Is it stamped as a National Semiconductor part? It is certainly possible that there are unlicensed Chinese clones floating around out there. There are a lot of very clever people over there, I remember years ago finding out that I had bought a batch 486DX2-66 chips which were actually 486DX2-50s, with the tops "planed" and re-stamped in China (came through an HK supplier). Boy was I upset, those chips were $660 each back then. I would test the chip, and if it works, use it. Would you mind posting a photo? Wes

20th August 2005, 01:49 AM	#5
wes-ninja250 diyAudio Member Join Date: Feb 2005 Location: Kingston, ON	Hey, Richard -- I happened to stumble upon this link and thought you might find it interesting: http://sound.westhost.com/counterfeit.htm Wes

22nd August 2005, 01:49 AM	#6
Richard.C diyAudio Member Join Date: Aug 2004 Location: China	haha, it's interesting.... i have a picture of my lm675t chip, and a picture of the compare of 675 and 1875 ,but i don't kown how to upload them to this forum

22nd August 2005, 02:19 AM	#7
Richard.C diyAudio Member Join Date: Aug 2004 Location: China	[IMG]675[/IMG]

23rd August 2005, 02:38 AM	#8
Richard.C diyAudio Member Join Date: Aug 2004 Location: China	help me! how to paste a picture in my post??