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Title: Valiant VFO - C18 Post by: wa2fxm on November 27, 2018, 06:11:03 PM Here's my Valiant VFO sitting naked on the bench. C18 the tubular 43pf NPO 500V capacitor is shorted. I understand that it is an ultrastable temperature compensating capactior used for VFO frequency stability. But it also seems to be the coupling capacitor between the actual oscillator circuit and the VFO tube, not a frequency determining capacitor. Is it critical to replace it with another NPO type capacitor? If so, are there special NPO type silver mica caps or will this one be a suitable replacement?
Mark - WA2FXM Title: Re: Valiant VFO - C18 Post by: DMOD on November 27, 2018, 06:23:04 PM C18's basic function is as a feedback capacitor to sustain oscillation and is a 43 pF 2.5% ceramic capacitor. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
I would use a 39 pF 5% 500V mica. Phil - AC0OB |