PSA - more bad TL072s

Laundryroom David

Laundryroom David

Keyboard Cowboy 🤠
If you’re troubleshooting a build that involves TL072s, don’t assume the chips are good even if purchased from reputable sources. I built a @szukalski Blue Sheep yesterday that just would not work. I narrowed it down to the ICs. Popped in known good NE5532s and it sounds awesome. The TL072s I was using were either from Digikey or SBP, so it’s def not a dodgy seller. Anyway, carry on building something! Hopefully this note will help somebody’s sanity.

EDIT: I traced this tube of chips back to a Digikey order.
 
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Cybercow said:
Did you note the batch ID? I've been collecting bad TL072 batch IDs that I find or get reported . . . .

Known Bad TL072CP Date Codes:
18MDSHY
14AP8NM
07A5L8QM
22ALE3M
Click to expand...
I've been paranoid ever since I read this, but never got around to checking ones I had until today. I have two with code 07A5LQM. Just one character less from a fake one!

These were in my stash, but I may have used some from the same batch in builds. So far I haven't had any that don't work, but if they were noisy not sure I'd notice.

I think I'm in the clear but the code is suspiciously close.
 
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Laundryroom David said:
If you’re troubleshooting a build that involves TL072s, don’t assume the chips are good even if purchased from reputable sources. I built a @szukalski Blue Sheep yesterday that just would not work. I narrowed it down to the ICs. Popped in known good NE5532s and it sounds awesome. The TL072s I was using were either from Digikey or SBP, so it’s def not a dodgy seller. Anyway, carry on building something! Hopefully this note will help somebody’s sanity.

EDIT: I traced this tube of chips back to a Digikey order.
Click to expand...
As an added note: The bad TL072s I noted with batch dates were from Tayda and only ever had the problems with their TL072CP devices. I prefer to use the TL072IP chips ever since. (Tayda does NOT carry the TL072IP.)
 
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So if they're the same performance and price, why DO you prefer the IPs? Just based on the dud CPs?



Also, ordering from TI itself may be the safest route, but (for example) 1 in every million spark plugs off the manufacturing line is a dud — I know this from experience: tuned up an engine and barely made it 900 km (probably started having problems about 600k in) on a 2320k round trip. "Couldn't be the spark plugs, they're all new!"





[above figures approximately 560miles/373miles/1442miles respectively]
 
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I found this really interesting article on the subject:
therepaircafe.wordpress.com

In Defense Of The LM358

Oh no… The LM358! An opamp loved by some, hated by many. What’s with it? The LM358 is a dual opamp that isn’t like the other girls. For example, it has the ability to drive its ou…
therepaircafe.wordpress.com therepaircafe.wordpress.com

There's also a video linked there that shows how to test your IC with either scope or meter.
 
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I can get a pretty good idea if an opamp is legit by measuring its power supply current and input bias current. If I'm still not sure, then I break out the scope and look at slew rate & output voltage swing. When I bought a quantity of LM308s a while back, I checked power supply current & slew rate. They were 100% legit.
 
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