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My NE555 chips gone bad

Fluffyboii

Member
https://www.reddit.com/r/synthdiy/comments/v2srqh
I made a sequencer for my future synth project and designed a circuit around baby10 design: https://hackaday.com/2016/01/14/oh-baby-baby10-build-a-classic-analog-music-sequencer/

I first wanted to test the oscillator part which is astable 555 and it is the most basic thing in existence but it refused to work properly. I gave up and decided to change the 555 I used and that kinda destroyed some traces but I carefully re-made those connections and tested it again. Which resulted the LED staying on but going a bit lower brightness state for a very small amount of time. Which was related to the resistance between pin 7 and VCC as it should be but still it wasn't the expected 555 behaviour where the LED turns on and turns off continuously with the same turn off and turn on time period. So I gave up on it, thinking it was a connection problem that I kept missing because I was tired.

Today I tested the same thing on breadboard and saw the same exact staying on and going a bit dark behavior which made me go insane. I tried all of the remaining 555 chips and one of them functioned fine and others had the same issue. Interesting thing is there were 3 Texas Texas Instruments NE555s and 2 of them had that problem and I also had another brand's 555 which had the same issue. One of the Texas ones worked fine which was identical with the others and probably bought at the same time which is interesting since broken ones aren't the same brand.

So the final question is, does NE555 chips go bad for no reason like this in the same exact way. The ones I have are at least 6-8 years old and they stayed in my electronic box for years until I needed one of them yesterday. I use to build flip flops with these with no issues in the past and it's simple circuit design is almost engraved in my mind.

Edit: the supply voltage is 12V which is below 16V max stated in the datasheet.
 
Last edited:

Dick Cappels

Active Member
I have used NE555's on and off for nearly 50 years and have not had one die of unexplained causes. Take a close look at your circuitry and the datasheet for clues. If you post your circuit here in schematic form we can probably be of further help.
 

Fluffyboii

Member
I have used NE555's on and off for nearly 50 years and have not had one die of unexplained causes. Take a close look at your circuitry and the datasheet for clues. If you post your circuit here in schematic form we can probably be of further help.
The problem was the schematic I used. It was set to have a very short pulse of voltage going low and mostly staying on at the pin 3. I did not realised this and assumed the chips gone bad because except one of them all of them worked the same way. So my assumption of them going bad was wrong and I wasted like 4-5 555 ICs. I wanted to use it with CD4017 to have a analog sequencer for my modular syth project. I changed the timer circuit and now it is working as I wanted it to be.
 

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