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Fake LM1875T - have I been had?
Fake LM1875T - have I been had?
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Old 17th September 2019, 05:17 PM   #1
Pentode is offline Pentode  United Kingdom
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Default Fake LM1875T - have I been had?

I bought some LM1875T chips from America - wrong they came from Bangkok.

Reading on the web there's every chance these are fakes..... would be grateful if you could have a look here IMG-0119 — imgbb.com and let me have your thoughts? I just can't recall or find the logo brand.


Dave

Last edited by Pentode; 17th September 2019 at 05:24 PM.
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Old 17th September 2019, 05:43 PM   #2
chermann is offline chermann  Austria
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Hi Dave


this chip looks used = 2nd hand. the pin legs are not conform with the original LM1875 because the legs starting bigger at the case and get smaller at the end.
on the top you can see some black ring and this looks definitely used.


as you can read in the other thread eBay mono LM1875 kit its not easy without lab equipment to check which kin of chip you get here. the safe side is 18V per rail!


chris
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Old 17th September 2019, 06:31 PM   #3
FauxFrench is online now FauxFrench  France
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Quote:
Originally Posted by Pentode View Post
I bought some LM1875T chips from America - wrong they came from Bangkok.

Reading on the web there's every chance these are fakes..... would be grateful if you could have a look here IMG-0119 — imgbb.com and let me have your thoughts? I just can't recall or find the logo brand.

Dave
Have you been had? Perhaps, if you paid a price similar to what you could have bought them for at a reputed US dealer.

If you, like me, have bought 10 or more at a ridiculously low price my opinion is you have not "been had". Most chips are manufactured in Asia, both genuine and fakes. You hardly get exactly the same product for 10-20% of the "genuine" US price.

The logo is National Semiconductor that is now owned by TI.
My LM1875s (probably not genuine) can handle rails up to +/-29.5V (I did not test higher) but have some stability issues above +/- 24V, which is also known from genuine LM1875s. Perhaps worse than for genuine.

I made a well sounding amplifier with these LM1875 and for a very modest price. THD seems correct. This is an experimental amplifier for trying out the LM1875, not an amplifier I will use many years ahead as my main amplifier. LM1875 is a very nice IC to work with because it has only 5 pins and is simple in implementation for a good result. For what I paid, I do not feel tricked.

If the LM1875 is not "genuine", what do we then get? A die-optimized (shrinked/shrunk) IC based on the original design? ICs that were discarded in the original production batch due to some spec. deviations? Reworked old items? If they actually work you can take a guess - but you may never know for sure.

If you want to be certain what you get, buy at a reputed dealer for the genuine price. Else, accept they will probably work for what you need and keep the rail voltages down to 18-22V as suggested by Chris. Sitting worrying afterwards will only irritate you.

Last edited by FauxFrench; 17th September 2019 at 06:40 PM.
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Old 17th September 2019, 07:26 PM   #4
Pentode is offline Pentode  United Kingdom
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I thought I was buying from a reputable company in America...! I bought 6 for about 17 (UK).

The legs and tab are a sure give-away, I looked and looked for the Logo and never thought of National Semiconductors, thanks for that info. I got them from Tayda Electronics in US, when I saw Bangkok on the package I did get 'that feeling', Knew I should have stuck to Radio spares or the like.... getting almost as bad as Ebay.... glad they weren't RF power transistors, yes I was aware the 1875's are like rocking horse manure these day's.

Guess there's only one way to find out. Ah, well there's still the LM3886, luckily the LM1875T wasn't for anything serious, I'll have a play and see what coloured smoke they give out, I don't mind blowing one for fun, I'll probably never used them for anything serious now I'm aware.

Thanks again for the info, Dave
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Old 17th September 2019, 07:47 PM   #5
Pentode is offline Pentode  United Kingdom
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Just been looking at the National semi. data sheet, tapered sides they say, these are square.... thought I'd just add.

Dave
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Old 17th September 2019, 08:38 PM   #6
FauxFrench is online now FauxFrench  France
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Yes Dave, I paid around 2.50 USD for 10 delivered from the far East. 17 for six must be close to "genuine" price.
If Tayda Electronics is aware of which are genuine and which are fake I do not know. It is a quest for us all.
Tapered sides or not may be an indication but not firm proof. Semiconductor manufacturers use varying wafer sites around in Asia. The documentation may have been issued with tapered sides while a wafer site later used a square house. As I recall it, mine at least have tapered sides.
Now you will be even more confused if they actually work and you do not see the magic smoke.
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Old 17th September 2019, 10:31 PM   #7
Naaling is offline Naaling  Portugal
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Tayda Electronics is a Thai company, that maintains a wharehouse in the US.

Tayda Electronics
167 Soi 28 Rama 6 Road
Samsennai, Payatai
Bangkok 10400
THAILAND
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Old 17th September 2019, 10:44 PM   #8
Pentode is offline Pentode  United Kingdom
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I'll make a couple of PCBs in the next day or two and build one up and see how far I can push one of em', if ya' see the moon with two faces give us a wave.

That's the place Naaling pointed out - just that I didn't look before ordering did I? All the flags were there waving right at me, if Radio Spares or similar didn't have them should have set red lights flashing.... but no not this time.
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Old 18th September 2019, 12:30 AM   #9
asuslover is offline asuslover  Romania
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Fake LM1875T - have I been had?
these are 100% authentic , bought from TI.com .
Where did you get yours?
Attached Images
File Type: jpg IMG_2369.jpg (161.7 KB, 212 views)
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Old 18th September 2019, 01:36 AM   #10
Dirttracker73 is offline Dirttracker73  United States
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I have purchased from Tayda many times, and to the best of my knowledge, everything has been genuine . I have not done extensive testing but everything has measured and functioned correctly with no failures or issues. This includes chip amp ICs, voltage regulator ICs, transistors, resistors, capacitors, and many miscellaneous hardware items. The only issue I've experienced was getting NXP branded transistors (BD139 & BD140) when the description shows STMicroelectronics (formerly SGS-Thompson) as the manufacturer. Not what I wanted but they seem to function acceptably.
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