I haven't determined the lot cod yet, I have a reel with date code: 1951 +5 and another reel with date code 1929.
We have a good number of boards failing. changing chip fixes half of them.
The part runs on a +5 V rail unity gain. We have the output of a DAC feeding the chip. at a input voltage of 4.9V and 5 V (max DAC) the output of the chip is about 4.25 volts.
I verified the chip mark of OAPI.
Any clue what could be the issue. The board has been well behaved until recently. I suspect the 1929 date code reel. it has a label from a distributor on it. I'll know more after they replace the bad chips with the ones from the 1951 + 5 reel next year.
Partial schematic of chip in use. I verified voltage at pin 3 of the op-amp and both sides of R17 (It isn't a leaky D1). Also no oscillation is seen on output. The rails are good (measured at the chip)
