2020-02-19 Nobility 15 transistor Radio Repair

2020 Feb 18 – Nobility 15 transistors OTL
S/N (?J)29549
I replaced the electrolytic capacitors. The spkr buzzed when I touched the volume control. Nothing from the detector (transistor). It’s unusual. I pulled and tested some IF parts including one of the transistors, no problems found – transistor tested good. I called it a night.

Next day, I tried to inject a low level 455 kHz modulated signal and got nothing. I wasn’t sure if I was getting output from the signal generator so I connected it to the RF input of a signal tracer, nothing. Instead, I connected the AF input of the signal tracer and I hear the modulated RF. That’s backwards! So I checked the signal tracer, detector diode was okay. I’m puzzled. Back to the radio, I probed around some, not getting anything. I probed the transistor next to the variable capacitor and it seemed to not be working. I unsoldered it and tested it and it tested okay. So I soldered it in and the radio worked! I don’t know what I fixed! ?? Weird! I put the radio back together and it’s working fine.

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