[time-nuts] Totally unrelated, but..

Bob Camp kb8tq at n1k.org
Thu Dec 8 16:58:34 EST 2016


HI

Ok, so to fully evaluate the problem, you will need to de-encapsulate the parts. That *is* the next step
in this adventure. First pass would be to pull the plastic off of a couple of bad ones and get some pictures
of the die. After that, trace them back and see if they are Brand A or Brand B. Next, do the same for a good 
one (or two) and see if the die trace to the same manufacturer. 

Next after the die are traced down would be probing with something like a Cascade probe system. You can
get them that are alleged to be good into the > 20 GHz range. Team that up with some low noise test gear
and you will be able to rule in / rule out the regulator it’s self. Yes this is a bit expensive. If you want to troubleshoot
the issue, it is the next step. 

It’s a whole lot easier to swap out the regulator for a different one and just move on. 

Bob

> On Dec 8, 2016, at 11:37 AM, Van Horn, David <david.vanhorn at backcountryaccess.com> wrote:
> 
> I did check the circuit through the whole range that it should operate in, based on component data sheets. No issues.
> I also carefully varied the voltage right around where the regulator output is, to see if there was some very narrow band of sensitivity.
> Nothing.
> 
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Joe Leikhim
> Sent: Wednesday, December 7, 2016 12:31 PM
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] Totally unrelated, but..
> 
> Could the low noise parts actually be counterfeit, relabeled as such?
> 
> Is the circuit the regulator feeds sensitive to a narrow band of voltage that the "good regulator" is outside of?
> 
> Try replacing the regulator with a battery supply and resistor divider to attain the working voltage. Move the voltage around. A good potentiometer and stiff filter capacitors are recommended so as not to introduce "pot noise".
> 
> Is something corrupting your test procedure?  I had a circuit that misbehaved due to floating logic pins reacting to static electricity on the work bench. Another time a diode was photosensitive.
> 
> 
> 
> --
> Joe Leikhim
> 
> 
> Leikhim and Associates
> 
> Communications Consultants
> 
> Oviedo, Florida
> 
> JLeikhim at Leikhim.com
> 
> 407-982-0446
> 
> WWW.LEIKHIM.COM
> 
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