Polyvaricon variable capacitor CBM-223F 202012.5mm FM 140p+60p. I'm thinking the Q of the tank is probably on the low side with the high - pf varicaps (I wonder if the 100k on the tuning voltage line is effectivly shunting the tank), and better just to the point where it works with the airspaced caps. Buy Variable Capacitor China Direct From Variable Capacitor Factories at. These capacitors provide the capacitance values so as to vary between 10 to 500pF. 1-16 of 481 results for 'variable capacitors' RESULTS Price and other details may vary based on product size and color. Charlie designed the tuner to work specifically with the polyvaricon variable capacitors that used to be sold by Mouser.
Its possible that one of those solder joints or a component is becoming microphonic. AFA the crackling issue youre having, check for any poor solder joints around the variable capacitor. Unfortunately, I dont have that issue in my library.
#Polyvaricon variable capacitor manual#
I was thinking of putting a largeish cap (0.01u) between the lower diode and ground, but if I did that there would be no dc path to ground for the diode bias voltage. Variable capacitors in general consists of interwoven sets of metallic plates in which one is fixed and the other is variable. Hey Peter, The service manual for your radio is in TSM-76. Yes I tried reversing the lower diode, after all dual varicaps are often common cathode, but that didnt work either. I dont have any mvam 2's, but I tried a couple of leds reversed biased as varicaps (the ground side one lights up), and I had the airspace cap in parallel too, it worked, but obviously there is very little tuning range from the 'varicap leds' like this. That said the circuit works well with a 20 - 500pf airspaced variable cap, and a 10 - 365pf polyvaricon.ĭo you think the o/p waveform is tuning the diodes and killing oscillation? There is a big difference between the mvam 2 and the bb510, the mvam 2 is 20 to 40 pf, the bb510 is 20 to 440pf.
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