TL 072 pin 1 not marked

[barber02]

I recently bought some TL072 ic from mouser and to my surprise there is not a pin 1 identifier. I haven’t been doing this work for very long but this is the first time I’ve seen this. Am I missing something obvious that I should just already instinctively know? I have already installed the new chips on the board (taking a guess) and I’m curious if I have the new chips installed correctly

David

 

[Perry Babin]

I've never see the print on a legitimately marked IC any way other than right-reading. Pin 1 would be the lower left.

 

[rayma]

Way too blurry, but sometimes there is a slight bevel on the corner (or side) for pin #1.

 

[MarcelvdG]

It's a pity that you already soldered them into a circuit, because the other stuff on the board may obscure things, but you could use a multimeter's diode test to check the polarity of the substrate diode between the upper left and lower right pins. It should have its cathode connected to pin 8 and its anode to pin 4 so it is in reverse when you apply a supply voltage.

 

[barber02]

Oh wow. That is a terrible picture. Sorry about that. About the time posted this my daughter called with a flat tire so I had to go take care of that.

Thanks for the input guys. I probably be able to figure out from your responses.

 

[MarcelvdG]

Thinking more about it, it doesn't really matter that they are already in a circuit. If you should measure a diode between positive and negative supply that is connected in forward, you know that there is something terribly wrong, so when the rest of the PCB is OK, it must be the TL072s.

 

[radtech]

Is one of the top edges beveled? If so, that side is pins 1-4.
That's what ST shows in their datasheet. Always download the datasheets when ordering parts, there's all kinds of information in them.

 

[rayma]

This is a side beveled package.
https://www.analog.com/media/en/pac...ge/pkg_pdf/ltc-legacy-soic/05081610_G_SO8.pdf

 

[barber02]

Oh. Ok. I didn’t look for the beveled edge. You’re right. I should have download spec sheet.

David

 

[barber02]

So I finally was able to get back out to the shop and check for the bevel edge and I found it. It looks like I got lucky and got the chips on the board in the correct orientation. The bevel edge is on the left. Talk about dumb luck.

Thanks for the help everyone. Much appreciated.

David

 

[dotneck335]

****-can the TL072 and use an OPA 2134. Much Much Better.