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kestrelmusic · 2nd Aug 2020, 6:27 pm

Many thanks for this. When you say the "low value mica capacitors", do you mean C9/C10 (100pF each) or the trimmers? I assume since the oscillator is running in MW and SW, C9 and C10 are OK, or would it be worth hiking them out and checking them or trying replacements?

I've already checked C15 (133pF) and it's very close to the correct value - certainly within 10%, probably better. That was the first thing I suspected as it's the only one in circuit only on LW.

The only other thing I can think of - a long shot? - is that the set has clearly been exposed to very damp conditions for a prolonged period; the chassis has a lot of rust top and bottom, and the IFTs and HT capacitor are quite corroded. I wonder if this may have affected the coil. If so, presumably replacement is the only option.

2nd Aug 2020, 6:27 pm	#3
kestrelmusic Hexode Join Date: Feb 2008 Location: Wrexham, North Wales, UK. Posts: 466	Re: Cossor 501 oscillator puzzle Many thanks for this. When you say the "low value mica capacitors", do you mean C9/C10 (100pF each) or the trimmers? I assume since the oscillator is running in MW and SW, C9 and C10 are OK, or would it be worth hiking them out and checking them or trying replacements? I've already checked C15 (133pF) and it's very close to the correct value - certainly within 10%, probably better. That was the first thing I suspected as it's the only one in circuit only on LW. The only other thing I can think of - a long shot? - is that the set has clearly been exposed to very damp conditions for a prolonged period; the chassis has a lot of rust top and bottom, and the IFTs and HT capacitor are quite corroded. I wonder if this may have affected the coil. If so, presumably replacement is the only option.