Hello everyone, I have been working on a simple audio amplifier. I received my PCB just yesterday, and I assembled it right away. Upon power up, the op-amp literally blew up.
After checking the circuit, I concluded it was a faulty op-amp, as I couldn't find anything else. I did a simple power-up test on the remaining op-amps (NE5534) I had. Out of 4, 3 went up about the same way. I had nothing else but the op-amp on the breadboard.
I applied +-12v. And they all sparked, and smoked immediately after I turn the power on.
The 1/4 that didn't blow up is working fine on my amplifier board.
Has anyone had such experience from eBay parts? I am not sure if this can happen with parts from places like Digikey?
After checking the circuit, I concluded it was a faulty op-amp, as I couldn't find anything else. I did a simple power-up test on the remaining op-amps (NE5534) I had. Out of 4, 3 went up about the same way. I had nothing else but the op-amp on the breadboard.
I applied +-12v. And they all sparked, and smoked immediately after I turn the power on.
The 1/4 that didn't blow up is working fine on my amplifier board.
Has anyone had such experience from eBay parts? I am not sure if this can happen with parts from places like Digikey?
There are countless reports of problem parts from auction sites, such as fakes, out of spec devices etc etc.
Parts from recognised suppliers are guaranteed to be full spec devices, and I'd go so far as to say its pretty much unheard of for any such parts to have a problem.
Another unknown is the circuit you are using them in. Incorrectly designed power supplies can sometimes do unpredictable things at power on. 78/79 type supplies in particular often need 'steering diodes' added to ensure correct start up.
Parts from recognised suppliers are guaranteed to be full spec devices, and I'd go so far as to say its pretty much unheard of for any such parts to have a problem.
Another unknown is the circuit you are using them in. Incorrectly designed power supplies can sometimes do unpredictable things at power on. 78/79 type supplies in particular often need 'steering diodes' added to ensure correct start up.
The surface of the DIP package looks suspicious …
My guess: They're fake. The forger(s) did not realise that the NE5534 is a single OP amp and used a cheap double OP amp (e.g. 4558 or TL072 or even NE5532). Then you would have connected +12V to one output of the double OP amp -> smoke.
My guess: They're fake. The forger(s) did not realise that the NE5534 is a single OP amp and used a cheap double OP amp (e.g. 4558 or TL072 or even NE5532). Then you would have connected +12V to one output of the double OP amp -> smoke.
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Ya I think I have to buy a couple more from Digikey and test it out using the same supply. I have been using +-12V from my computer power supply. Other than the voltage measurement using DMM, I have no clue how reliable the power is. Is a benchtop power supply (from Amazon for ~$100) a good one to start?
I tried on a breadboard. +-12V and only the IC on it. It still blew up. Or should I have placed some by-pass caps?
Yes, I think I have to shop from Digikey more often. Their minimum for free shipping is $200 =(. Oh well!
I checked and double checked that I was placing the IC correctly.
How do you tell if might be fake? I thought it was weird that it didn't have a dimple to mark pin 1.
Well, how could you know that you put it in the right way around, then?
Haha good point. It however had NE3353 printed on the top surface. Pictures I have seen online showed both dimple and the NE5534 printed on it. So I assumed the same orientation.
Ah, true! Well, let me get a couple more from Digikey, and test it out the same way I did. If nothing blows up, it at least means my power supply is good, and that I need to avoid eBay parts..
You could insert your lone survivor backwards now, to see if it fails the same way. That would kinda' proof that the other three were marked upside down.
Haha well, my *lone survivor* is already soldered into the board. I don't think it wants to be bothered, seeing how its friends went. And I have been trying this in my garage squinting my eyes.
Ok, I realized I had 2 more NE5534 in my drawer. From another seller, as these have dimples. I plugged into my power supply the same way as before, and neither blew up!
2 is a pretty small sample size, but the previous batch had more than 50% of failure rate. So I think I can blame faulty NE5534s.
Ya the dimple seems *printed*, not marked. I guess I have to use authentic parts from Digikey anyways.
Whoa.. That looks quite premium(?). Ya mine may have been relabeled. Gonna get a few more of these from digikey. Gr hardware engineering is expensive
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Please post the EBay link to the page/seller .
I'd *love* to see his sales History.
Ye, definitely sanded down and remarked.
NO WAY they miss *both* the end notch and the pin 1 dimple, it's either one or the other.
And labelling is NOT an indication.
Not sure about the economic justification about this, meaning an IC which is still widely available; now if it were some mythical unobtanium semiconductor, well, it might be different.
Of course, seller might have some 10000 duds to dispose of , so anything is possible.
I'd *love* to see his sales History.
Ye, definitely sanded down and remarked.
NO WAY they miss *both* the end notch and the pin 1 dimple, it's either one or the other.
And labelling is NOT an indication.
Not sure about the economic justification about this, meaning an IC which is still widely available; now if it were some mythical unobtanium semiconductor, well, it might be different.
Of course, seller might have some 10000 duds to dispose of , so anything is possible.
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