[ARC5] AN/URM-90...

[WA5CAB--- via ARC5]

Actually ZM-3/U and ZM-3A/U are capacitor analyzers.  AN/URM-90 is an R-L-C 
bridge, and the nomenclature of the main component is ZM-30/U, not ZM-3/U.

On the ZM-3, I have a ZM-3A/U that replaced a Sprague TO-6 years ago and 
that I use regularly for reforming capacitors, and also as a megger.  Once in 
a while I also use either of the other two functions.  The quick fix to the 
spring return switch problem is to simply remove the spring (and tie wrap it 
inside the unit).  Later, I removed the switch from one unit (I have three) 
and machined the cam to make it detented in all three positions instead of 
detented in two and spring return in the third.

I've never had a ZM-30 and don't have any manuals except for calibration 
procedures so am not familiar with it.

On the analog versus digital question, digital is not inherently more 
accurate than analog.  It is just less prone to operator error.  And can be a 
great time waster as you sit and fiddle with adjustments trying to get that 
last digit dead on zero.  :-)

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 05/08/2015 09:22:57 AM Central Daylight Time, 
k1lky68 at gmail.com writes: 
> On May 8, 2015, at 7:36 AM, DSP3 <jeepp at comcast.net> wrote:
> 
> >Actually, its a rather nice, albeit manual,  RLC bridge (meter).
> 
> Yes, in deed.  It is a true boatanchor bridge.  The instrument itself is 
> called the ZM-3. I used mine to reform capacitors.  It helps in this work to 
> have a wine bottle cork to hold the “apply voltage” lever switch in 
> position while the cap is charging/reforming.
> 
> It is kind of a kluge to operate, but it does a lot.  Take the time to 
> learn how to run the thing.  Modern solid state gadgets are fast and 
> *apparently* accurate, but no where near as fun to use.
> 
> I have a copy of the manual in digits if you don’t find that online (Bama 
> may have been the source of mine, or LOGSA back when that was useful for 
> such manuals.)
> 
> Roy
> 
> 
> >  For what you get, however, the newer digital instruments are a lot 
> easier to use.   If its in nice condition, why not keep and (occasionally?) use 
> it?  The _book_ is a necessary item!  For what it may be worth, one of the 
> MRCA group members sold one at Berryville last year for about $20. Someone 
> got a pretty good deal...
> >
> >Jeep - K3HVG
> >
> >On 5/8/2015 12:59 AM, Kenneth G. Gordon wrote:
> >>I found one of these in my stash. What's it good for?
> >>
> >>Ken W7EKB