I am working on a pair of Ludwig Jahnke germanium pre amps (see attached circuit). There is a filament bulb (12v 120mA) between the output pair of transistors (part 81). On one of the preamps I am dealing with this bulb has blown.
EDIT. I originally thought these were germanium because of the negative supply, but looking up the transistor numbers all transistors are in fact Silicon
Questions.
1. I am guessing the bulb is to keep some sort of bias on transistor part 78. Is this the case, & does the voltage across the bulb change during operation ?
2. Can I sub a diode in or does this circuit need to have a bulb there ?
Thanks
Rob
EDIT. I originally thought these were germanium because of the negative supply, but looking up the transistor numbers all transistors are in fact Silicon
Questions.
1. I am guessing the bulb is to keep some sort of bias on transistor part 78. Is this the case, & does the voltage across the bulb change during operation ?
2. Can I sub a diode in or does this circuit need to have a bulb there ?
Thanks
Rob
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