Polymorph analog VCO

Far as I know it’s always been the case that some chips have half circle notches, some have indented circles at the pin 1 end… and some have half circle notches at the pin 1 end and indented circles at the other end.

It’s stupid, but it’s always been stupid.

What is always true is if the label text is right side up, pin 1 is lower left.

My systems work on ±12V and have reversed the polarity numerous times (I screw up a lot) and have never had let the smoke out our fried the chips. I use TL072, TL074, LM358, and LM324. Never fried a one. I did have a electrolytic capacitor explode once. You have to be very careful with those as they are little grenades when the go pop!

The only half moon markers I have seen are on Texas Instruments chips. Most other chips have just a little nipple, dot, or inlaid circle at pin one. Those pictured are quite typical.

As a practice, I test for continuity and shorts before applying power on a new board. I can never emphasize the importance of a good quality bench meter for testing. If you are working on a lot of boards, for the money you can’t beat the Siglent SDM3045X. If you are on a tighter budget (I have this as a backup) you should have the OWON XDM1241. The handheld DMMs are OK but I found the bench DMMs have many more hidden features that I have found very helpful.

An old analog oscilloscope is extremely useful as well. I practically stole one on ebay years ago. While it isn’t tightly calibrated it is so useful to be sure waveshapes are correct and levels are decent.