Radio Philips 09RB098 tunes with difficulty and interference
Hi, pr122, yes, they are loud squeaks, they appear when tuning in, once a station is tuned in, they disappear completely. Here in my city there are 3 AM radios and 3 I can tune them, although it costs to be tuned for those squeaks that get. Regards.
It is not a potentiometer problem, since once the station is tuned in, the fact of giving more or less volume does not generate any squeaking.
Another detail in the operation is that the stations are picked up again but at higher frequencies, for example 780 kHz, it is also possible to capture it at 1,100 kHz (approx.), 900 kHz also at 1,300 kHz (approx.).
The problem of repeated stations has to do with the image frequency, that is, the station is repeated at a frequency equal to twice the IF. If the FI is 150 KHZ, a station will be tuned again to 300 KHZ. If the FI is 200 KHZ, the station will listen again at 400 KHZ. The problem is that a station is separated at 300 KHZ, and another at 400 KHZ, so the problem of the FI is ruled out, and that it is a problem of the local oscillator, as I commented in the other post. Nothing to do with the harmonics that pr122 comments.
Thank you very much Nico4706 for your conceptual explanations of what an image frequency is. And so I referred then to review in detail the variable capacitor. I checked some discontinuity at the point where the tip of the shaft makes contact with the capacitor body. At that point there is a tiny copper neck that helps better contact between these 2 parts. It was covered on both sides of a waxy patina. I sanded it on both sides with a fine sandpaper.
I imagine this was the problem, since the interference and tuning mirrors immediately disappeared. I reiterate my thanks to pr122 and Nico4706 who had the patience to answer my question. And according to how my tests go, I would like to raise the case of another radio of the same model that working well one day, the next nothing comes out. A dilemma for me. Regards.
hello, every component to test must be disconnected at least one leg in capacitor diodes and resistors, and 2 legs in transistors, this is to avoid, that there may be erroneous measurements to be another components welded between legs, the capacitors, should be changed if there is doubts, and if you do not have a capacimeter, to put in frequency the coils you need more elaborate instruments, greetings
Thank you, pr122. I tried to see what happened when desoldering the S (Shield) leg of transistor 2SA341 and no major change was perceived, so I am inclined to think that it is the complete transistor that no longer works well, so I will test it desoldered and eventually replace it with one of a radio that works well, although that would be like undressing a saint to dress another. Then it would help me to know what replacement of this transistor exists these days. As an additional fact (although I don't know if I contribute anything significant), I injected an IF signal through the antenna and it was clear.
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