[SI-LIST] Re: Fw: Re: Inexpensive TDR for short/open localizing on a PCB
- From: "Patrick Jabbaz" <patrick@xxxxxxxx>
- To: olaney@xxxxxxxx
- Date: Thu, 3 May 2007 12:26:20 -0700
Another simple way of determining where the short is, is to use a ohm meter,
well you will need an ohm meter that can read very low values, I have used
this in the past to find Power ground planes shorts very effective, it will
narrow down the location to about half an inch.
Patrick Jabbaz
Ubiquiti Networks
495-499 Montague Expwy
Milpitas, CA 95035
T: (408) 942-3085
M: (408) 621-6533
On 5/3/07, olaney@xxxxxxxx <olaney@xxxxxxxx> wrote:
>
> Lee is probably right. This is the sort of thing that I recommend be
> purchased used, either through a dealer for a refurb'ed unit with a
> warranty, or else e-bay if bottom dollar is the goal. My shop is very
> happy with an Agilent 54754A dual TDR that includes differential
> measurements (better than equivalent Tek gear in my opinion due to a
> superior implementation) and TDT. Spatial resolution is about a quarter
> inch, or if well calibrated and some noise is tolerable, down to nearly a
> tenth inch. A plus is that the 54754A is not just a TDR, but also
> doubles as a dual channel sampling scope with a bandwidth of 18 GHz. The
> 86100 mainframe includes automated analysis of risetime, eye patterns,
> etc. and includes export of screen shots that can be pasted into a
> document, etc. If only a single channel is required, the 54753A is
> cheaper. You can get the 86100A used. The current 86100C is required
> only if you demand new or need the jitter analysis capability. Agilent
> also sells an articulated probe holder that does a lot to solve the
> problem of connecting the TDR to PCB traces (N1020A). This is a
> universal fixture that can be used with any TDR, and can also be found
> used. The PWB fabrication industry uses a lot of TDR equipment from
> Polar Instruments. That might be another direction to check. The
> capability seems more modest than full blown lab gear, which is probably
> sufficient for casual troubleshooting of the sort that you contemplate,
> but I don't know if it is necessarily cheaper.
>
> I'm hesitant to reply to the entire list, because the automated "out of
> office" replies are a pain in a tender place. Why there isn't a facility
> to suppress auto responses to list servers speaks to why so much software
> is terrible -- it's written by programmers rather than by users.
>
> Orin Laney
> Atwood Research
>
>
> Jerry,
>
> The least expensive TDR I know of that will suit you purpose is the
> Tektronix 1502C.
>
> Lee
>
>
> > [Original Message]
> > From: Jerry Martinson <jmartinson@xxxxxxxxxxxxxxxxx>
> > To: si-list <si-list@xxxxxxxxxxxxx>
> > Date: 5/2/2007 10:54:14 AM
> > Subject: [SI-LIST] Inexpensive TDR for short/open localizing on a PCB
> >
> > Sorry if this seems a bit off-topic.
> >
> >
> > Does anybody know of an inexpensive and easy-to-use TDR system that's
> > good enough to localize PCB assembly shorts and open with accuracy that
> > translates into about 1 inch on a trace? I'm trying to see if I can
> > find something that can help out with the old "which chip to replace"
> > problem during assembly debug as often BGA x-rays are ambiguous.
> >
> >
> >
> > Jerry Martinson
> >
> > ARUBA NETWORKS
> >
> > (work 408-754-3037) (cell 408-394-5185)
> >
> > jmartinson@xxxxxxxxxxxxxxxxx
> >
> > 1322 Crossman, Sunnyvale, CA 94089
> >
> >
> >
> >
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