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Actually, in doubt I had replaced C16 and R16... One thing I didn't mention, though, is that at the beginning I was getting no 38 kHz at all, due to a faulty C15. It is only after replacing C15 that I got the 38 kHz back... but slowly decreasing when L5 was heating. I wonder if the fact that the coil had been feeding the ECF80 plate (for years, perhaps) without oscillation isn't the cause of its damage. Chris

@dl2jas - additional measured values: adjusting tuning, the inductance varies from 4.8 mH to 5.55 mH @oldiefan - good point! I'll mention it to the coil maker @kugel-balu - yes, I had tried with two new ECF80 @chriss_69 - you're right! Although I suppose the theoretical value would be 1.3 mH, but the measurement is not accurate enough. I have just sent a request to Reinhöfer. Do you know of other coil makers I could inquire from? Thank you, best regards, Chris

Hi, Here are some measurements of L5. Inductances are measured at 10 kHz. Resistances are measures with a multimeter, accuracy not better than 10%. Looking at the schematic, the three connections are Schwarz (+230V), Rot (output, connected to C17), and Grün (plate of ECF80 penthode). - Between Rot and Grün: 5,5 mH, 5.4 ohm; - Between Schwarz and Rot: 1.38 mH, 2,5 ohm; - Between Schwarz and Grün: 1.41 mH, 3.0 ohm. How I analyse that: - the overall inductance (5,5 mH) matches the value obtained vi…

Hi Reinhard, Thank you for your suggested options. A) I do intend to take L5 out and make some measurements. However, I don't think the wire is broken, as it does not completely stop working. My best assumption at this stage is that the insulation between windings is faulty, and this places a resistance in // with the inductance when hot, thus dampening the resonance. If I have the specs of the coil (via measurements or documentation) I will try to wind a new one or have it wound by Reinhöfer. B…

Hi Michael, Here are the schematic, and the layout. The coil in question is L5. Thanks! Chris

Hi, I repair lots of Saba automatic radios in Canada. Today, I am struggling to revive a Saba FM Multiplex Adapter 12, and have an issue with the coil L5 (doubler 19->38 kHz). The doubler works, but after some minutes the 38 kHz voltage drops significantly. If I cool the coil (with cool spray) the voltage is back up again…(supply voltage is correct and stable, the 19 kHz voltage at the oscillator coil is perfectly stable). Therefore I conclude that the coil L5 is faulty (insulation failure when …