Question on Western Electric 259A Tube Characteristics
John Byrns
Hi All,
Thanks to a generous group participant, I now have a copy of the
modification notes for modernizing the Western Electric No. 10-A Radio
Receiver. As I had originally suspected when I first heard of these
modifications, they were designed to reduce the detector distortion, and
improve the AGC action, eliminating the effect of modulation on the AGC.
What I didn't get right was the reason for replacing the RF amplifier
tubes with more modern types. The photo of a modified receiver that I had
seen used the RCA metal tubes, so I assumed that the modifications were
designed in the late 30's, or 1940's, and the reason for changing the RF
tubes was simply to use a current tube, that was more easily available.
As it turns out the modifications were designed in the mid 1930's, when
the 10-A would have only been a few years old. The modification
instructions said to replace the WE 259A tetrodes used in the RF amplifier
stages with RCA 58 pentodes. There were also penciled in notes to use the
later 6K7 metal tubes, as I had seen. The use of 6K7's would have
required replacing the heater transformer, I need to find that photo, and
look for evidence of a new heater transformer.
The modification instructions state that the reason for replacing the WE
259A tetrodes with the RCA 58 pentodes, was because of the poor distortion
performance of the 259A's at high RF signal levels. This brings me to my
question, does anyone have a data sheet for the 259A tube, who could tell
me what sort of tube the 259A was? Specifically was it just a straight
"sharp cutoff" tetrode, or did it have some "remote cutoff" action? Also
was the heater Voltage 2.5 Volts, or some other less standard Voltage?
Thanks in advance for any help with information on the 259A tube.
Regards,
John Byrns
Surf my web pages at, http://www.enteract.com/~jbyrns/index.html
Alan Douglas
John Byrns asked:
>The modification instructions state that the reason for replacing the WE
>259A tetrodes with the RCA 58 pentodes, was because of the poor distortion
>performance of the 259A's at high RF signal levels. This brings me to my
>question, does anyone have a data sheet for the 259A tube, who could tell
>me what sort of tube the 259A was? Specifically was it just a straight
>"sharp cutoff" tetrode, or did it have some "remote cutoff" action? Also
>was the heater Voltage 2.5 Volts, or some other less standard Voltage?
2.0 volts, 1.6A
It's not remotely remote (sorry). At a plate voltage of 162 and a
screen of 65 (per the 10A test specs) a 259A would cut off abruptly
at -8V.
73, Alan
nes...@my-deja.com
WE
> 259A tetrodes with the RCA 58 pentodes, was because of the poor
distortion
> performance of the 259A's at high RF signal levels. This brings me
to my
> question, does anyone have a data sheet for the 259A tube, who could
tell
> me what sort of tube the 259A was? Specifically was it just a
straight
> "sharp cutoff" tetrode, or did it have some "remote cutoff" action?
Also
> was the heater Voltage 2.5 Volts, or some other less standard Voltage?
>
>
is understandable that they would want to change to a semi or full
remote cutoff type for improved IM distortion at high signal levels and
improved AVC performance. What is the WE 10-A radio, anyway? I am not
familiar with it and am wondering who would and/or why it would be
modified? As you say, changing the sockets to octal on the RF sections
of a commercial set is not a task for the neophite and, indeed, not one
to be entered into lightly.
--
Neil S.
Vancouver, B.C.
> Regards,
>
> John Byrns
>
> Surf my web pages at, http://www.enteract.com/~jbyrns/index.html
>
Sent via Deja.com http://www.deja.com/
Before you buy.
John Byrns
> Since you now have the information that the 259A is a sharp cutoff, it
> is understandable that they would want to change to a semi or full
> remote cutoff type for improved IM distortion at high signal levels and
> improved AVC performance. What is the WE 10-A radio, anyway? I am not
> familiar with it and am wondering who would and/or why it would be
> modified? As you say, changing the sockets to octal on the RF sections
> of a commercial set is not a task for the neophite and, indeed, not one
> to be entered into lightly.
> --
> Neil S.
> Vancouver, B.C.
>
Hi Neil,
The Western Electric No. 10-A Radio Receiver is an AM Broadcast Tuner
built by Western Electric in the early 1930's. It was used in commercial
sound installations, such as radio systems for hotels, where a number of
receivers were used, along with powerful amplifiers to distribute multiple
radio programs to the hotel rooms. The 10-A is a TRF Receiver using 3
sets of double tuned Band Pass tuning circuits, tuned by a six section
tuning capacitor. It is noted for its unusually wide audio bandwidth.
The WE 10-A is interesting to me because it is the progenitor of a whole
string of radios using similar circuits, from J.W. Miller, Collins Audio
Products, and Meissner. There was also a construction article by W.N.
Weeden published in the February 1937 issue of Electronics Magazine, which
described a Wide-band receiver design inspired by the 10-A circuit. With
the exception of the 10-A which uses three double tuned circuits, all
these receivers use only two double tuned circuits and a four section
tuning capacitor. The Meissner design, which dates from the 1950's also
uses a slightly different coupling arrangement between the two coils of
each double tuned pair. The Weeden receiver is my favorite among all
these, I consider it to be the best designed of the lot.
Schematics for the WE No. 10-A, Weeden's Wide-band Tuner, and the J.W.
Miller True Fidelity Tuner can be found on my Web Site at the following
URL:
http://www.enteract.com/~jbyrns/BP-TRFs.html
If anyone knows of other similar TRF radios using double tuned circuits
for selectivity, I would be interested in hearing about them.