The 8056 (P/N 154-0417-00) is a low-voltage Nuvistor triode tube with a 6.3 V heater.
It is used in the 422, 502, early W, 1S1, 3A7, early 3S3, 3T4, 5T3, and 10A1. It can sometimes be replaced with a MPF102 FET.
The 8056 has a maximum plate-to-cathode voltage of 50 V. Contrast this with another Nuvistor triode, the 7586, which has a maximum plate-to-cathode voltage of 110 V (however, one of the 8056 test conditions for 157-0099-00 puts 100 V on the plate.)
The 7586 and 8056 have the same pinout, but the two tubes are not interchangeable since they have different voltage ratings.
For example, in the front-end cathode followers of the 3A1, the plate voltage of the 7586 tubes, V113 and V123, is 55 V, and possibly a bit higher during warm-up. This exceeds the maximum plate voltage of the 8056, unless the 3A1 is modified for lower front-end plate voltages.
|Aged/Checked/Matched Pair Details|
|Used in||Tek Part#||S/N Range|
|502, W, 3A7, 10A1||157-0099-00||All|