eBay purchased NE5534s literally went up in smoke - diyAudio
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Old 7th December 2015, 04:40 AM   #1
b1gtuna is offline b1gtuna  Canada
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Default eBay purchased NE5534s literally went up in smoke

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?

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Old 7th December 2015, 06:39 AM   #2
Mooly is offline Mooly  United Kingdom
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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.
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Old 7th December 2015, 08:20 AM   #3
AndrewT is offline AndrewT  Scotland
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That blow up could be due to a bad part, or it could be a bad circuit causing destructive oscillation.
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Old 7th December 2015, 08:32 AM   #4
Enzo is offline Enzo  United States
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I know many people successfully shop on ebay, but as an operator of a commercial pro audio repair facility, I never buy such parts. ANy small savings in price are overcome by experiences such as yours. Suppliers like Mouser or Digikey have never let me down.
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Old 7th December 2015, 09:05 AM   #5
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If the ic is put in a socket the wrong way around or the supply voltages are muddles up, that will happen.
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Old 7th December 2015, 09:17 AM   #6
mat02ah is offline mat02ah  Germany
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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.

Last edited by mat02ah; 7th December 2015 at 09:19 AM.
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Old 7th December 2015, 02:49 PM   #7
b1gtuna is offline b1gtuna  Canada
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Quote:
Originally Posted by Mooly View Post
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.
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?

Quote:
Originally Posted by AndrewT View Post
That blow up could be due to a bad part, or it could be a bad circuit causing destructive oscillation.
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?

Quote:
Originally Posted by Enzo View Post
I know many people successfully shop on ebay, but as an operator of a commercial pro audio repair facility, I never buy such parts. ANy small savings in price are overcome by experiences such as yours. Suppliers like Mouser or Digikey have never let me down.
Yes, I think I have to shop from Digikey more often. Their minimum for free shipping is $200 =(. Oh well!

Quote:
Originally Posted by JonSnell Electronic View Post
If the ic is put in a socket the wrong way around or the supply voltages are muddles up, that will happen.
I checked and double checked that I was placing the IC correctly.

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Originally Posted by mat02ah View Post
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.
How do you tell if might be fake? I thought it was weird that it didn't have a dimple to mark pin 1.
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Old 7th December 2015, 03:20 PM   #8
Preamp is offline Preamp  Germany
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Quote:
Originally Posted by b1gtuna View Post
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?
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Old 7th December 2015, 03:24 PM   #9
b1gtuna is offline b1gtuna  Canada
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Originally Posted by Preamp View Post
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.
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Old 7th December 2015, 03:27 PM   #10
Preamp is offline Preamp  Germany
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Like everybody else would have done, I guess. But then again, how did the "manufacturer" made sure he got it right prior to marking the device? Looks fishy...
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