Conversion Examples
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Bias Network, Etc. Below are several examples of the conversion process. I've analyzed a famous germanium project book and come up with substitutions for base bias resistors and other parts. The silicon replacements require twice the base bias voltage of germanium parts. (Silicon transistors turn on at 0.7 vs. 0.3 volt for germanium transistors.) Fixing the bias allows the silicon to amplify or oscillate. Yet you might run into other problems, such as spurious oscillation. Silicon's superior gain might cause this oscillation. You can fix this problem by adding negative feedback to the circuit. The book is: Buckwalter, Len. Easy to Build Transistor Projects. New Augusta, IN: Editors and Engineers, Ltd., 1965. Volume 619 in this publisher's Skillfact™ Library. |
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Replacement parts. See the table below. Replacement parts in the table allow contemporary transistors to operate in circuits with obsolete germanium transistors. Such transistors include Raytheon's CK722 and GE's 2N107. The Buckwalter book uses these obsolete types.
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| Replacement Parts for Buckwalter | |||||||
| Transistor: Use 2N3906 or 2N2907 (in every case). | |||||||
| Audio transformer: In every case, use 1000Ω CT to 8Ω. (Available from Radio Shack stores, or RS online) | |||||||
| Chapter | 1st Resistor | 2nd Resistor | 3rd Resistor | Capacitor C1 | Capacitor C2 | Capacitor C3 | Audio Transformer |
| 1 | No circuits appear in Chapter 1. | ||||||
| 2 | R1 = 1.2M | R3 = 390K | (None) | As in book | As in book | As in book | As above |
| 3 | R1 = 1.2M | R3 = 390K | (None) | (None) | (None) | (None) | As above |
| 4 | R1 = 3.9M | R3 = 2.2M | (None) | As in book | As in book | As in book | (None) |
| 5 | R1 = 390K | (None) | (None) | As in book | As in book | As in book | (None) |
| 6 | R1 = 390K | R2 = 2.2M | (None) | As in book | As in book | As in book | (None) |
| 7 | R2 = 820K | R4 = 820K | (None) | As in book | As in book | As in book | (None) |
| 8 | R1 = 10M | R4 = 390K | (None) | 0.47 μF | 0.0047 μF | 4.7 μF | As above |
| 9 | R1 - R6: Multiply value * 5 | 0.01 μF | As in book | (None) | As above | ||
| 10 | R1 = 1.2M | R3 = 620K | R5 = 390K | As in book | As in book | As in book | As above |
| 11 | R1 = 2.2M | R3 = 620K | R5 = 390K | As in book | As in book | As in book | As above |
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