Burroughs MBST Specifications  
Written by Accutron on 2009-06-17  

For photographs and historical information, please refer to the Beam Switching Tubes section of our electronics museum.

Key to Electrical Characteristics

F: Switching Speed
Et: Target Voltage
It: Target Current
Rt: Target Load Resistance
P/ta: Individual Target Dissipation
Es: Spade Voltage
Rs: Spade Resistance
Ecc: Grid Bias Voltage
Ej: Grid Switching Voltage
GZ: Grid Zero
Esg: Shield Grid Voltage
Ef: Heater Voltage
Ih: Heater Current
Ehk: Heater-Cathode Voltage
Eco: Firing Voltage


Prototype

Burroughs manufactured a number of unusual prototypes, including radial trochotrons and specialized BCD coding tubes. Little is known about these devices, and most types have no known examples.

Type Envelope F Et It Rt P/ta Es Rs Ecc Ej GZ Ef Ih Ehk Eco Notes
DC-1                             20-pin base.
DC-1R                             9-pin base; uncharacterized pin configuration.
TR-BC-11                               BCD coding tube, sleeve-type anode.
TR-DC-11                               Counter, sleeve-type anode, internal spade resistors, 9-pin base. Same as DC-1R?
TR-SR-11                               Selector, sleeve-type anode. Same as DC-1?
SEL-10                               Radial internal configuration.
AF-12                               Experimental noise source. External magnet, B13B base.



Standard Envelope

The earliest production types, represented by the 6700 and 6701, are the earliest types to be produced in quantity. These early models have a large cylindrical external magnet, plastic end caps, and no mu shield. Later on, Burroughs introduced shielded variants of these large models, making the final package even larger and more than twice as heavy. Some of the early models feature 'grid zero', where grid even, position zero can be triggered separately for faster resetting. In the standard 26-pin base, pin 11 is unused. In the grid zero pinout, grid zero is on pin 16, and the remainder of grid even is moved to pin 11. Additionally, Burroughs manufactured 10MHz types with internal spade lead resistors and an atypical 20-pin base.

Type Envelope F Et It Rt P/ta Es Rs Ecc Ej GZ Ef Ih Ehk Eco Notes
6700
HB-101
MO-10
2MHz 100VDC
+/-10%
5.5mA 3.3k 1W 100VDC
+/-10%
100k 25VDC -50V No 6.3VAC
+/-10%
300mA +/-90VDC 200VDC First production MBST, originally manufactured with Haydu label.
6701 1MHz 20VDC
+/-15%
0.6mA 6.8k 1W 20VDC
+/-15%
270k 12VDC -20V Yes 6.3VAC
+/-10%
300mA +/-90VDC 50VDC Low voltage, low speed variant of 6700 with grid zero.
BD-300 2MHz 100VDC
+/-15%
6.5mA 3.3k 1W 100VDC
+/-15%
100k 25VDC -50V Yes 6.3VAC
+/-10%
300mA +/-90VDC 200VDC Variant of BD-301 with grid zero.
BD-301
6703
2MHz 100VDC
+/-15%
6.5mA 3.3k 1W 100VDC
+/-15%
100k 25VDC -50V No 6.3VAC
+/-10%
300mA +/-90VDC 200VDC Shielded variant of 6700 with slightly higher target output and cathode current.
BD-308 1MHz 20VDC
+/-15%
0.6mA 6.8k 1W 20VDC
+/-15%
270k 12VDC -20V Yes 6.3VAC
+/-10%
300mA +/-90VDC 50VDC Shielded variant of 6701.
MO-10R
6704
10MHz 100VDC
+/-10%
5.5mA 3.3k 1W 100VDC
+/-10%
100k
Internal
25VDC -50V No 6.3VAC
+/-10%
300mA +/-90VDC 200VDC High speed variant of 6700; internal 100K spade resistors, 20-pin base
BD-309 10MHz 100VDC
+/-10%
5.5mA 3.3k 1W 100VDC
+/-10%
100k
Internal
25VDC -50V No 6.3VAC
+/-10%
300mA +/-90VDC 200VDC Shielded variant of MO-10R.
BD-311 2MHz 130VDC 10mA 3.3k   130VDC 82k 30VDC -70V   6.3VAC 300mA     High current variant of 6700.
BD-401                              



Compact Envelope

First-generation beam switching tubes were large, heavy and expensive. Burroughs responded to the size issue by engineering a reduction in the diameter of the spade cage, which allowed for a corresponding reduction in the envelope, magnet and shield diameter. The miniature envelope style has a primary envelope diameter that is significantly smaller than the base of the envelope, flaring outward just above the pins to accomodate the size of the standard 26-pin base. Such tubes were also available in shielded and unshielded varieties, the shielded types being of the same diameter as a standard-size unshielded model.

Type Envelope F Et It Rt P/ta Es Rs Ecc Ej GZ Ef Ih Ehk Eco Notes
BD-203 1MHz 55VDC
+/-10%
3mA 3.3k 1W 55VDC
+/-10%
130k 25VDC -50V Yes 6.3VAC
+/-10%
150mA +/-90VDC 100VDC  
BD-316 1MHz 55VDC
+/-10%
3mA 3.3k 1W 55VDC
+/-10%
130k 25VDC -50V Yes 6.3VAC
+/-10%
150mA +/-90VDC 100VDC Shielded variant of BD-203.
BD-400                              



Beam-X Switch

Reducing the size of the spade cage was a a limited solution. The so-called miniature tubes were still fairly large and fairly heavy, especially the more common shielded types. In 1960, Burroughs introduced a more radical solution. They returned the envelope to its original larger size, large enough to accomodate a new design with internal magnets.

These advanced tubes, sold under the Beam-X Switch trademark, have 10 small internal magnets and add a signal-improving shield grid. Beam-X Switch tubes are much smaller, lighter and faster than their external-magnet predecessors: the unshielded BX-1000 and BX-3000 are the smallest beam switching tubes ever produced, and are the size of a first generation tube minus the magnet and shield. Shielded Beam-X tubes are only slightly larger, and can be installed adjacently.

The Beam-X Switch pinout is identical to the standard 25-pin configuration, but adds the shield grid on pin 11. Unfortunately, this leaves no available pins for a grid zero reset function. Like earlier models, Beam-X Switch tubes were manufactured in both shielded and unshielded types.

Type Envelope F Et It Rt P/ta Es Rs Ecc Ej Esg Ef Ih Ehk Eco Notes
BX-1000
6710
2MHz 55VDC
+/-10%
2.7mA
+/-30%
3.3k 1W 55VDC
+/-10%
150k 40VDC -55V 55VDC
+/-10%
6.3VAC
+/-10%
150ma
+/-10%
+/-100VDC 100V First Beam-X switch, multiple internal variations.
BX-1202                              
BX-1203
6713
                             
BX-1204                              
BX-2000
6711
2MHz 55VDC
+/-10%
2.7ma
+/-30%
3.3k 1W 55VDC
+/-10%
150k 40VDC -55V 55VDC
+/-10%
6.3VAC
+/-10%
150ma
+/-10%
+/-100VDC 100V Shielded variant of BX-1000.
BX-2001                             High current variant of BX-2000.
BX-2003                              
BX-2004                             Used in 101P479 programmer.
BX-2005                             Used in 101P479 programmer.
BX-2012 2MHz 55VDC
+/-10%
2.7ma
+/-30%
3.3k 1W 55VDC
+/-10%
150k 40VDC -55V 55VDC
+/-10%
6.3VAC
+/-10%
150ma
+/-10%
+/-100VDC 100V BX-2000 specially tested for decoding BCD.
BX-2013                              
BX-3000
6712
2MHz 80VDC 5mA 3.3k   80VDC 150k 50VDC -55V   6.3VAC 150mA     High current variant of BX-1000.
BX-3001                              
BX-4000 1MHz 30VDC 1mA 10k   30VDC 270k 26VDC -24V   6.3VAC 150mA     Low voltage, low speed variant of BX-2000
BX-4001
6714
2MHz 30VDC 1mA 10k   30VDC 270k 26VDC -24V   6.3VAC 150mA     Standard speed variant of BX-4000.

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