This circuit (attached) takes a 0-1mA input and converts it to 4-20mA loop powered at 24V.
Some BOM items:
IC1 = LM358N
CR2 = 1N5300 (1.30mA Current Regulator Diodes)
Q1 = HARRIS D44C2 or SOLID STATE D44C8
CR3 = LM329BZ (6.9V Precision Voltage Reference)
As you can tell from the scan, this is old. It has worked for decades, but now it draws around 90mA when powered up from a fast-rising supply.
A slow ramp up to 24V does not show the issue.
I don't want to muddy the waters at the moment, but does anyone have any pointers?
I had thought it might be latch-up or output phase reversal but I'm not sure now.
thank you.
Edited to clarify: this circuit thas been in production for decades without issue. Only recently the problem has been observed on newly built circuits. Looking at the parts list, a few things have gone obsolete over the years and replaced by equivalents (mostly same part number, different manufacturer)
Alternatives are listed for IC1:
NSC LM358N
ST MICROELECTRONICS LM358N
FAIRCHILD SEMICONDUCTOR LM358N