Originally Posted by Richard Knoppow

"Hank" wrote in message
...
In article
,
Richard Knoppow wrote:

"Clutter" wrote in message
...
On 05/19/2012 12:08 PM, Richard Knoppow wrote:
"Renan

wrote in message
...

Hi everyone, I am looking for a VR-300 ,( 95 - 130
volts,
60Hz Voltage
Stibilizer ) used In BOONTON Q Meter 190A. Please, If
available, let me
know the value. Thank you in advance!


There are two mailing lists that may be of help.
One
is
the Agilent-Hewlett-Packard list and the other is the
Boonton list.

http://groups.yahoo.com/group/hp_agilent_equipment/

http://groups.yahoo.com/group/Boonton/


Thanks for the Yahoo groups info. I didn't know about
those two.
I joined the Boonton group as I have a couple of 260A's
both in
need of repair to some degree. Now if I can just find
some
time
to work on them...


There are probably a few people on one or the other
of
those groups who know the 260A well. At -hp- all the
Boonton stuff was done by a couple of specialists who did
nothing else. I think the 260A is reasonably easy to get
operational, the 250A RX meter was a bear to get
calibrated
and the older 160A Q-Meter requires a special tube which
was
selected. Boonton liked using selected tubes, one of the
202 series RF generators used three tubes of the same type
but selected for different characteristics. A royal PITA.
There have been a couple of other Q meters made but
the
260A is still an excellent instrument. The trouble is
that
most people now have no idea of what they do or how to use
one.

I have to chuckle at the idea that people don't know the
value of
Boonton Q meters and the 250A RX bridge. I cut my teeth
on the 160A
and 190A Q meters and the 250A when I went to work for
James Millen in
1956.

Forty years later, when equipping a bench for doing some
serious work
with boatanchors, I located a 260A---got it working, but
it was a
cosmetic horror, so when someone gave me a non-working but
cosmetically clean 260A with a tentative diagnosis of a
burned-out
thermocouple, I took it. However, it turned out that the
thermocouple
was not burned out, just had a bad solder connection at
one end of the
heater wire.

The 260A (as I recall, a 1953 redesign of the mid-1930's
160A) is not
particularly difficult to work on. Biggest problem I
found with both
was poor contact with the oscillator turret pins and open
oscillator
coils. The open coils all were breakage at the turret
pins, very easy
fix. But the brass pins and contacts took abrasive work
to get them
to make contact. DeOxit D-5 didn't touch them.

The 160A used a selected 45 tube for the oscillator, and
the
thermocouple burned out quite easily. The 260A uses an
off-the-shelf
tube--5763 as I recall---so that component is a
plug-and-play
replacement. The 260A thermocouple is much more robust.
I've
forgotten what was in the 190A, though I've been inside
all of them at
one time or another. The VTVM tube is selected in all of
them.

Boonton supported these units with excellent manuals which
go into
great detail about how they can be use. That's true of
the RX Bridge
as well. The Q-meters are not at all difficult to
calibrate by the
procedures given by Boonton.

When push comes to shove, there is nothing like a good
Q-meter when
dealing with boatanchor front-end and IF coils. One
strand of broken
Litzendraht drop the Q of a coil significantly, and having
a Q-meter
available to get the exact capacitor needed for a
silver-mica failure
makes life very simple. Of course, a Measurements
Megacycle Meter or
Millen Grid Dip complement them nicely, but aren't
substitutes.

The 250A RX Bridge was, I think, a bit daunting for
1930's/1940's
radio EE's. The Chief Engineer at Millen, Wade Caywood,
bought one
for the company, and spent quite a bit of time
experimenting with how
best to use it. Mine came out from under a table at a
hamfest---not
working, but looked brand new, and when the guy said he
wanted $20 for
it I swapped cash for the bridge and immediately took it
out to my
car. All that was wrong with it was that the Amperex
ballast tube was
open, so no voltage to the IF strip heaters. I just used
wire-wound
resistors to set the voltage. I don't recall having to
fix any
oscillator problems, but the mica dialectric in the little
capacitor
at the front of the bridge had to be reglued in place
(Pliobond). The
bridge was calibrated after it was assembled, so you
really do not
want to fuss with it.

I'd have to say that to get real mileage out of these
boxes,
particularly the RX bridge, you've got to know a bit more
than you're
going to learn from the ARRL Handbooks or Fred Terman's
texts.

I have used the Marconi Q-meter, which also uses a special
(read
"unobtainium") tube, but you have to have both of the
power
oscillators that go with it. Heathkit made a Q-meter kit
that was
patterned after the Boonton, but simplified. I had one of
these for
years, and got quite a bit of use out of it, but the 260A
is a step up
in capability and accuracy.

I'm not sure what Boonton was thinking when they put the
voltage
stabilizers in the Q-meters and the ballast in the RX
bridge. Unless
your primary power is seriously off-voltage, I don't see
that they are
needed.

Hank


The 190A uses a diode rather than a thermocouple. The
diode runs, I think, in its square-law region and is the
only tube in the instrument that was selected. I don't know
what measurements were made on this tube. The meter scale
will not track properly if the tube characteristics are not
right. However, the tubes are very long lived and can not
be burned out.
The thermocouple in the 260-A is much harder to damage
than the one in the 160-A but one must still use some care
in setting the oscillator level.
Both handbooks have pretty good texts on Q and its
significance and additional literature was available from
Boonton, most, if not all, of which is on the web.
A couple of standard coils for the meters are useful
for checking but overall calibration, as you say, does not
need them. Working coils are very easy to make.
The RX meter requires some study, it is not a general
purpose bridge. Mainly, the Q-Meters are intended for
relatively high-Q circuits and the RX-Meter for low-Q
circuits. The RX meter is excellent for measuring the RF
characteristics of resistors.
All three of these guys, but especially the RX-Meter
are true boatanchors:-)



--
Richard Knoppow
Los Angeles
WB6KBL