Ok, 308 Detectives

[Ginsly]

I'm loathe to do this, but... this look legit? Luckily the photog (not me) took an impeccable photo so this should be easy.

Not a huge deal either way, I'm not about to go crankin out several Rats or anything. Guess I'll have to grab a couple and test em to know for sure, but thought I'd see if this was an easy fake to spot. It's a person I know and sounds like they've had em for quite a while, though. No way they're gonna do any testing! yay

 

[jwin615]

The date code gets me. Anyone seen a NatSemi date code with XX?
The other kicker is the logo itself. That's not the logo used in 1978.
In 75 they moved from

To

Which they used until 94

The only thing that would explain it to my caveman mind is maybe the found some NOS completed dies in the 90s and packaged them 18ish years after fab?

 

[Ginsly]

The only thing that would explain it to my caveman mind is maybe the found some NOS completed dies in the 90s and packaged them 18ish years after fab?

Hey J - might be my old desktop, but that second pic is just a black square for me!

Yep I can't find any pics of an XX code either... hmm

I had found this in an Aion tracing journal, and he dates a chip with "82" on it as a 1998 NS somehow:

 

[EricGuitar]

 

[jwin615]

It has a transparent backbround.
Dark mode strikes again.

 

[EricGuitar]

Top row 4th fourth from the left M71XX all legit ones

 

[Ginsly]

Top row 4th fourth from the left M71XX all legit ones

There it is, an XX - thanks for this! Huh, they might be legit! I figured it was likely, as these have probably been sitting in a drawer for maaaaany years.

 

[jwin615]

That one looks painted or something

 

[jwin615]

And that logo wasn't used until the 90s.

 

[Ginsly]

And that logo wasn't used until the 90s.

Yep the similar one Aion dated as being from 1998 has "82" on it . Not sure how the date codes go during that period...

 

[jwin615]

YYWW

 

[Ginsly]

YYWW

Right, but assuming Aion was able to correctly date that chip somehow, the "82" doesn't correlate with a 1998 production directly. If both XX chips shown here were also from the 90's then that rings true of the "78" and "71" as well... hmm

 

[jessenator]

Reject modernity; return to TO99

 

[Ginsly]

Reject modernity; return to TO99

Detective Designation: Denied

 

[jessenator]

They're easily formed into DIP-8 pattern. Heck, they even sold SKUs bent from the factory that way.

 

[Ginsly]

They're easily formed into DIP-8 pattern. Heck, they even sold SKUs bent from the factory that way.

Ha, oh I know! They're very cool but go for a little more than the 3 bucks a pop I can get these DIPs for. I have a pretty nonexistent budget due to all of those Western Electric diodes I bought.

Looks like there were actually some HZ cans in the PPCB shop at some point..? Were those ever in stock?

 

[Ginsly]

Calling @aion - Kevin, how did you suss out that the M82AD chip mentioned above was from 1998? I assume you also tested it and deemed it legit?

 

[Cybercow]

This may help to identify the authenticity of a 308 opamp . . . .

 

[Ginsly]

This may help to identify the authenticity of a 308 opamp . . . .

I don't have them in hand, but if/when I do this is one of the diagrams I've bookmarked! Seems like you can also breadboard a Rat and pull the compensation cap to see how that changes things.

 

[jcpst]

Post in thread 'Pandoras Box Fizzle'

May 6, 2025

LM308 test
Build this circuit on a breadboard:
LM308 pin 2 to pin 6.
pin 3 to gnd via 100K.
Pin 3 to +9V via 100K.
Pin 4 to GND.
Pin 7 thru a DMM set to measure μA to +9V.
Apply power and measure current into pin 7. Typical current draw is 300μA. I have measured as low at 250μA and as high as 360μA. Most other single opamps draw at least 1mA.

H11F1 test
Build this circuit on a breadboard:
H11F1 pin 1 to a 1K resistor.
Other side of 1K resistor thru a 5K trimpot to +9V.
H11F1 pin 2 to GND.
H11F1 pin 4 to GND.
10K resistor from H11F1 pin 6 to +9V.
Apply power and measure the...

• Chuck D. Bones

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