[HBQRP] Weird NE555's?

[Dan Reynolds]

I cross posted this to 4SQRP also.

I bought some NE555 chips from the watery auction site, they are marked TI
and some of them are giving me strange results.

 

A while back I built a code practice oscillator, the ARRL one that if you
etch their board you can make a  key and everything. I'm just using the CPO
part of the design. I built it Manhattan style and it worked perfect. I was
attempting to learn/teach code and was using it on Sunday nights before our
clubs net. Sort of an informal over the air FM simplex practice session. (My
secret plan was to re-learn code by teaching).

 

Back to the NE555's. A couple of guys wanted me to make them a CPO. I got
the chips today and I put one in my original CPO and it worked but as soon
as you let up on the key there's a faint downward sweeping sound. Very short
but also very obvious. So, I tried it in my newly constructed units - same
thing. So, I started going through all the chips - I bought 20! 

 

So far out of 8 I've tested six of them have this behavior. I've used junk
box parts but my original 555 (no name) and at least (2) of these new ones
work correctly.

Before I go chewing this guy out I wanted to check with the experts here and
see if you think that might just be a 'normal' abnormality of this circuit
and the NE555.

 

Link to PDF of this design:
http://www.arrl.org/files/file/Technology/tis/info/pdf/NYT.pdf

 

 

Dan Reynolds - KB9JLO

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