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