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Friday, September 22, 2023

Tube of the Month : The 6BD11


This month we have yet another Compactron cutie: The 6BD11.

The 6BD11 is very similar to the 6AF11 which I presented last month. It has two triodes and a pentode integrated into one tube.

There is a medium mu and a high mu triode section and the pentode is of the sharp cut-off type. The two triode sections are almost identical to those of the 6AF11 except for slightly different maximum plate dissipation ratings. The pentodes also differ in plate dissipation and also have somewhat different plate resistance and transconductance. The 6BD11 and 6AF11 share the same pinout. In most applications these tubes would be pretty much interchangeable. I wonder what the reason was to develop two such similar tubes and register them under their own designations. Unsurprisingly the similarity between these two types also reflects in their plate curves. Here we have the data sheet curves and actual curves of each section, starting with triode nr 1:

Triode section 2:

The Pentode:

The pentode triode wired:

Moving on to some tube pics.

The 6BD11 from different angles:

Some more views of the tube:

The glass removed:

Removing one of the triode sections from the rest.

As expected the internal construction is very similar to the 6AF11.

The heater:

Cutting off the screen between the two triodes:

The second triode:

The pentode:

And lastly the tube in operation:

Stay tuned for yet another Compactron tube next month!

Best regards


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