OP-AMP Long-Term Reliability

Many solid state devices from that era are still running. Physical damage (moisture working in via the leads) is one primary cause of failure. If the leads look good then chances are fairly good the device will work.

I use lots of 30 to 40+ year old components all the time for servicing our classic arcade games. Most are perfectly good. Other than electrolytic capacitors...they definitely have a shelf life/best before date!

John :-#)#

The problem components from that era are lytics of course and glob-top transistors.

NT

OK, I have to know.. "Glob-top"??

No sign of corrosion at all on the leads.

So do I. The question wasn't about NOS components, but components that have been in service for decades.

The round top is an epoxy glob covering the die, which sits on the flat thick sheet material that holds the leads. 2 tone ones make this easy to see, all black ones not so much.

NT

My first sentence in my first paragraph was my (getting tired of 'my') experience about original esolid state devices still running.

Do please read what is written, I'm the only one here who is allowed to make the mistake of not reading entire posts before responding!

John ;-#)#

Ah. Ok. I have a few hundred of those but some obscure part numbers and all PNP so are unlikely to be called into service here. :)

Those bring back not so fond memories. The black potting epoxy was optically transparent to infrared light. I had a hell of a time dealing with weird problems in the 1960's until I found the light sensitivity problem with those transistors. It took about a year for Fairchild to clear their inventory and screw their unsuspecting customers by continuing to sell these devices. Eventually, they changed over to the "PN" (TO-92) style package, which initially was made from silicon epoxy instead of epoxy-B. Silicon epoxy shrinks slightly at high temperatures, causing the corrosive fluxes from the wave soldering equipment to creep up the transistor leads by capillary action, and corrode the leads and chip. We had to x-ray the dead parts to determine the failure mode and guess the cause. It usually took about a month for the transistors to rot to death. I had a difficult time getting Fairchild to understand that having *ALL* the transistors on a PCB fail almost simultaneously after only a month was sufficient grounds for suspecting that something might be wrong with the parts. They eventually switched to epoxy-B, but only after again unloading their defective inventory on unsuspecting customers. There was also a problem with the UA2136 IF amp/detector IC, where chips made in different Fairchild factories produced radically different performance and stability. I took great pride in personally removing Fairchild from the approved vendor/manufacturers list, and finding alternate sources for about $2.5 million/year of their components. When I mentioned this to the sales rep, he acted like he didn't care or it wasn't important.