555 Timer damaged or working

[electronicslearner77]

Hi All,

I have a 555 Timer IC, when I check the continuity using a multimeter of the pins 1 and 8 I found the continuity (shorted) and also I observed continuity between other pins. Does it mean that the IC is damaged?

Thanks and regards,
satya

 

[simonbramble]

Probably. Or it could mean that you have a short circuit elsewhere on the circuit board - if it is mounted on a circuit board. Get another one and try again

 

[ericgibbs]

Hi All,

I have a 555 Timer IC, when I check the continuity using a multimeter of the pins 1 and 8 I found the continuity (shorted) and also I observed continuity between other pins. Does it mean that the IC is damaged?

Thanks and regards,
satya

hi,
Your multi meter has an internal battery which it uses as a current source when measuring resistance.

When you try to measure a semiconductor device like a 555, the battery voltage at the ends of the test probes is high enough to turn on parts of the internal circuit of the 555, so you will get 'resistance' readings.

If pins 1 and 8 show a short circuit, as Simon suggests , the 555 could be damaged.

Testing with the 555 wired into a circuit can give confusing readings.

 

[electronicslearner77]

Hi,

I have disconnected the 555 timer IC entirely from the circuit board and tested it, still it shows short. I think the IC is damaged, I will try with another one.

Thanks for the replies,
Regards,
Satya

 

[electronicslearner77]

I have brought two new 555 timer ICs but still they are showing short in some pins, why is this happening? i am unable to understand. could somebody please help me?

thanks and regards,
satya

 

[electronicslearner77]

I do not know how it is working, i have just gone ahead building the circuit with the new 555 timer ics and found the circuit working even with the pins showing short with multimeter as i have mentioned above.

thanks and regards,
satya

 

[ericgibbs]

I do not know how it is working, i have just gone ahead building the circuit with the new 555 timer ics and found the circuit working even with the pins showing short with multimeter as i have mentioned above.

thanks and regards,
satya

hi satya,
Why would you want to measure the internal resistance of a 555 that you had not tried in a circuit to see if was defective, anyway.??

I was under the impression that the circuit would not work, thats why you tested the 555.

What ohm range did you have the meter set too.?

 

[meowth08]

Hi,

If you have deboarded the IC and still pin 1 and pin 8 are shorted, you might have a defective IC.

But since you bought another IC, and you tried testing it for shorts and you got the same result,

could you not consider YOUR TESTER to be defective?

meowth08

 

[electronicslearner77]

Hi Eric,

Just now I found out with my friend that it is a defective multimeter and gives continuity test (buzzer sound) because of some problem with slots where you insert the probes (I did not really shown interest to understand the exact reason). Thank you for your replies.

Thanks and regards,
Satya

 

[meowth08]

Hi,

So cool i'm right! That's what I learned from my on the job training at TI. That one is called "isolation"

m8