03-29-2024, 10:36 AM
Hi Jim,
Those are symptoms of an oscillator's failure to oscillate or oscillating at the wrong frequency. Since there are very few parts in this circuit, recheck the value of resistor 10 and I assume you replaced the 2 caps which make up part 20, which is a dual 0.1 mfd cap. Be suspicious of part 13, 110pf. When it comes to oscillators I narrow my tolerance on part values because it seems some oscillators are designed on the edge of whether they run or not. Any variation in part value may kill it. Also, do more checking on component connections, especially dirty switch contacts and tube socket pins. Try replacing the 6A7. You should see 2-4 volts on pin 4 of the 6A7 if the oscillator is running (use a DVM or VTVM). Clean the band switch contacts.
Those are symptoms of an oscillator's failure to oscillate or oscillating at the wrong frequency. Since there are very few parts in this circuit, recheck the value of resistor 10 and I assume you replaced the 2 caps which make up part 20, which is a dual 0.1 mfd cap. Be suspicious of part 13, 110pf. When it comes to oscillators I narrow my tolerance on part values because it seems some oscillators are designed on the edge of whether they run or not. Any variation in part value may kill it. Also, do more checking on component connections, especially dirty switch contacts and tube socket pins. Try replacing the 6A7. You should see 2-4 volts on pin 4 of the 6A7 if the oscillator is running (use a DVM or VTVM). Clean the band switch contacts.
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