The TX21 is a triode hexode frequency changer for use on 200 mA heater chains. It is thus suitable for both the AC and DC mains that existed in the 1930s.![](../pics/acn0072a.jpg)
The B7 base and pins.Thanks to Mark Mallison for sending the images.The wide glass tube envelope is mm in diameter and excluding the B7 base pins, is mm tall.Reference: 1043. Type TX21 was first introduced in 1936. See also 1936 adverts. |
Pin Connections
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | tc | ![](../static/key.gif) a(t) | g1(t),g3 | g2,g4 | h | h | m,k | a | g1 |
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Absolute Maximum Operating Conditions¶
| Vh | Ah | Va | Vs | Vg | mAa | mAs | ra | gm | ![](../static/key.gif)
| 21.0 | 0.2 | 250 | 80 | -1.5 | 5.5 | 6.0 | 1M | 1.0 |
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Absolute Maximum Operating Conditions¶
| Va | Vg | mAa | gm | ![](../static/key.gif)
| 150 | -1.5 | 4.0 | 1.2 |
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Updated April 16, 2022.
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