Hi All. Sadly, my KT-5020 tuner has developed an intermittent fault. It works perfectly but every so often, it has started to produce no audio at all. This presumably is because something in the "front-end" is failing as the display shows zero signal strength when the sound disappears. If I leave it switched on, it will suddenly work normally again after a few seconds of making a rustling sound in the output, then normal clear audio. Sometimes switching off after the fault appears occasionally gets it working again normally when switching back on. Could someone help me here please?. I could fix it but have no hands on with tuner fault finding at all. I attach the circuit diagram. Many thanks for reading. The file is safe to open.
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As a diagnostic, tune the unit to a frequency where its LO emission (10.7 MHz above nominal) can be received by a second radio, and watch what happens to that. If the LO signal momentarily goes away when the dropouts happen, I would put my bets on bad solder joints in the oscillator section or the power feed. Some poking and prodding with something non-metallic and/or inspection with magnification may reveal potential culprits.
