kb2vxa
Member
 Offline
Posts: 162
I modulate, therefore AM
|
 |
« Reply #4 on: December 25, 2019, 09:23:09 AM » |
|
Beware of NOS carbon comp resistors, heat isn't the only thing that makes them drift out of tolerance, age is a big contributing factor.
If you think I'm nuts I don't mind, it's always a good idea to test any kind of resistors you buy or have in your goodie box, they may be out of tolerance from the factory. On my last job as electrical QC inspector I also did incoming. For one job I had to sort 1% metal film resistors into 3 groups of very tight, something like .001% tolerance with a super accurate NIST calibrated Wayne Kerr analyzer. They were supplied by a big name company, so you would think they'd be within marked tolerance, right? No such luck, every one was WAY out, so I took them to the plant manager who returned them and received another batch. Guess what? Yep, THEY were no good either, the manager threw a fit! I could never blame him for getting upset over any problem, every job was working against a deadline. That's how it is making components for military contractors, a late delivery not only results in loss of the contract, but also a heavy fine, it's serious business! All is well that ends well, the third delivery was OK and we finished just under the wire. <whew>
You can save yourself a lot of grief wondering why your latest project went haywire, NEVER trust a supplier's QC, always do your own so Justin Case prevails over Murphy. I'm giving you this "warning" simply because those resistors, brand new metal film resistors, were SO far out of tolerance I wouldn't have believed it if I didn't experience it myself. You may never have this problem, but you'll always come out on top when you make friends with Justin Case.
|
