UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

orbanp1 · 6th Nov 2014, 3:44 pm

Hi Miguel,

When the bands move on the scale the local oscillator frequency is different. The components that are on the PCB and are part of the resonant circuit of the LO could cause this.
Looking at the schematics, C39 and C43, 1nF and 68pF respectively, has some effect on the LO resonant frequency.
See if those capacitors have the same values.
Different parameters of the oscillator transistor T1, like the collector capacitance (Cc), could also cause shifting of the oscillator frequency.

Peter

6th Nov 2014, 3:44 pm	#33
orbanp1 Heptode Join Date: Nov 2009 Location: London, Ontario, Canada Posts: 675	Re: Restoring my old Soviet radios Hi Miguel, When the bands move on the scale the local oscillator frequency is different. The components that are on the PCB and are part of the resonant circuit of the LO could cause this. Looking at the schematics, C39 and C43, 1nF and 68pF respectively, has some effect on the LO resonant frequency. See if those capacitors have the same values. Different parameters of the oscillator transistor T1, like the collector capacitance (Cc), could also cause shifting of the oscillator frequency. Peter Last edited by orbanp1; 6th Nov 2014 at 3:57 pm.