Burroughs BX-1000 Series  
Written by Accutron on 2006-10-11  

Devices included in this entry:

Burroughs BX-1000 unshielded Beam-X Switch (small shield grid variant; pictured in thumbnail)
Burroughs BX-1000 unshielded Beam-X Switch (large shield grid variant)
Electronic Enterprises BX-1000 unshielded Beam-X Switch (large shield grid variant
Burroughs BX-1003 unshielded Beam-X Switch
Burroughs BX-2000 shielded Beam-X switch

The BX-1000 is the first and best-known of the Beam-X Switch tubes. All susequent BX variants retain a nearly identical construction, though material and internal dimensional changes in later BX types result in various application-specific characteristics. The BX-1000 is capable of stable operation up to 3 MHz, and the tube's theoretical limit is around 4.5 MHz, assuming an ideal drive circuit with zero external spade capacitance. Burroughs never published a speed rating higher than 2 MHz, but internal developmental documentation confirms the higher attainable speeds. The earliest BX-1000s have smaller shield grid dimensions than later examples.

The BX-1000 is perhaps the most noteworthy for being far more substantially documented than any other type of beam switching tube. This is in stark contrast to subsequent Beam-X types, many of which are unregistered and seemingly undocumented part numbers.

Subsequent variations of the BX-1000 include the shielded BX-2000 and uncharacterized BX-1003.

Burroughs 6710 (BX-1000) Datasheet (PDF)
Burroughs ETM-149: Characteristics of Beam-X Switches in the Megacycle Range and Summary of Basic Operation (PDF)
Nixie Indicator Tubes: Characteristics & Circuit Design Data (PDF)

The BX-1000 has several internal variations which might suggest a change in electrical characteristics, though no such change is ever indicated in official Burroughs literature. The earliest BX-1000 tubes have slender shield grid elements, approximately 2mm wide. Newer examples have larger 4mm shield grid elements. All other Beam-X Switch types which have been internally examined (BX-1003, BX-1203, BX-1204, BX-2004, BX-2012, BX-3000, BX-3001) have large shield grid elements.

The other observed internal variation relates to the dimensions of the target magnets. Most BX-1000 tubes have magnets measuring 38mm in length, as do the two known examples of BX-1003. All other Beam-X Switch types which have been internally examined (see above) have 33mm magnets. Additionally, there are a few known specimens of BX-1000 equipped with 33mm magnets.

Most examples with small shield grids lack the 6710 part number on the external print, labeled as 'TYPE BX 1000'. Later examples with large shield grids are labeled as '6710 (BX-1000)'.

Early BX-1000 variation with small shield grid and no registered part number.

BX-1000 carton, circa 1960. It's unusual to find a BX-1000 in a old style carton such as this one. The tube is packed in a fiber roll and includes a socket - the tube equivalent of a development kit.

BX-1000 carton, another early style.

Most BX-1000 devices, including pre-6710 examples, were boxed in a much smaller white and blue carton with a molded white styrofoam insert and no socket.

Later variation of BX-1000 with a large shield grid.

Electronic Enterprises BX-1000, a rare rebranded version with a large shield grid and 33mm magnets.

The rare and uncharacterized BX-1003, 1965 date code. This device is presumed to be a BX-1000 variant.

Burroughs BX-2000, a shielded BX-1000 variant.

This article is part of the [Beam Switching Tubes] exhibit.

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