EEVblog #727 - How To Kill An Opamp

[Flump]

The yellow ones are faster !

[Excavatoree]

The price of those things has gone waaay up on eBay lately:
Lucky I got mine when I did.   
(You can still get the grey ones for a reasonable-ish price, but who wants a grey one?)

I always wondered why that is.

The yellow ones are faster !

OK, that explains that, but what is the benefit of the black sticker?

[mtdoc]

dave sell me that fluke 27 pleeeease 

The price of those things has gone waaay up on eBay lately:

http://www.ebay.com/sch/i.html?_nkw=fluke+27

Lucky I got mine when I did.   


(You can still get the grey ones for a reasonable-ish price, but who wants a grey one?)

The real value there is in the kits that include the high voltage probe. A Fluke 27 with a high voltage probe included for $75 is still a good deal IMO.

[Fungus]

The real value there is in the kits that include the high voltage probe. A Fluke 27 with a high voltage probe included for $75 is still a good deal IMO.

Yep. For $75 it's still a nice meter to have, even without the probe. Very solid/accurate/safe.

I'm just saying I got mine for $60 sometime last year, in case, with HV probe + all paperwork, in as-new condition.

Edit: I just saw this: http://www.ebay.com/itm/221724077442 

He has three ... grab 'em while they're hot!

[Fungus]

The price of those things has gone waaay up on eBay lately:
Lucky I got mine when I did.   
(You can still get the grey ones for a reasonable-ish price, but who wants a grey one?)

I always wondered why that is.

The grey "FM" models are actually better than the yellow ones - they have an extra chip for true RMS readings.

[Excavatoree]

The true Fluke 27 type connoisseur doesn't consider the yellow meters FMs, regardless of what the US government or a label says.   If it's not TRMS, it's not an FM.   (Ok, it's really only me, but I think everyone should agree with me - LOL)

[mtdoc]

The grey "FM" models are actually better than the yellow ones - they have an extra chip for true RMS readings.

Good point but be aware some that say 27/FM on the back label (not the front) apparently are not TRMS.

See this for more info on Fluke 27s

[HeywoodFloyd]

Thanks for this interesting little video. I am amazed how my small electronics projects have been resilient - when I have inadvertently picked up the wrong transistor - it didn't work, but the magic smoke did not escape and the component kept working (when used correctly). However I now tend to set the current limit on my power supply to well below 400 mA because that's where the fuse in the DMM blows

[tszaboo]

So just for completeness:
It is generally not a good idea to run precision equipment without input protection. An ESD event not necessarily kills the device, but it can silently knock it outside the calibration range. Add that it is a bare board handled by people with their hands, hopefully with ESD strap.

I know, that Dave knows this, and he mentioned that he needed the board faster than possible.

[Fungus]

I know, that Dave knows this, and he mentioned that he needed the board faster than possible.

And that it's only meant for use by testers in controlled environments.

[Neilm]

It happens to everyone. Many years ago, I was testing a system and reversed a pair of leads from the old calibrator I was using for a test. Unfortunately for me, I had forgotten that the calibrator did not have isolated outputs - the result was it shorted the mains supply out with a nice loud bang - and vapourised a 3mm track.

On the plus side for Dave, he has managed to get a successful repair video made.

[drcheap]

I recently had a capacitor that, during prototyping a mains voltage level circuit, I forgot to bleed after dis-assembly.  Later on when I was cleaning up the bench I found the cap, and it wasn't well marked, so I stuck it in my component tester to get a quick answer on the rating.  Well I got a quick response from the tester alright...ka-pow!

Nothing like a mains-charged cap discharging straight into the GPIO of a microcontroller expecting 5V

At least I had picked it up by the casing and not the leads!  Although I might have been taught a more memorable lesson from a personal zap vs. the $18 worth of tester damage.

[AlfBaz]

I recently had a capacitor that, during prototyping a mains voltage level circuit, I forgot to bleed after dis-assembly.  Later on when I was cleaning up the bench I found the cap, and it wasn't well marked, so I stuck it in my component tester to get a quick answer on the rating.  Well I got a quick response from the tester alright...ka-pow!

Nothing like a mains-charged cap discharging straight into the GPIO of a microcontroller expecting 5V

At least I had picked it up by the casing and not the leads!  Although I might have been taught a more memorable lesson from a personal zap vs. the $18 worth of tester damage.

I had a bit of a fright years ago when I racked out three banks of 600V DC BUS capacitors from a large variable speed drive. Tested the first 2 and saw the DC voltage rapidly falling thanks to the bleed resistor. Didn't bother with the third and presumed they were all discharged after a few minutes. Proceeded to work and put my 6" shifter on top of the 3 bank, I near shit my pants, that banks bleed resistor had failed open

Murphy is indeed a prick