The little rusty boy is alive! - SBR R1 - Part 2

[@xsc1000]

Its strange that it is hot chassis radio and it has phono input connected directly to chassis. In other radios there was always small insulation transformer for this input. Also ground and antenna were separated from chassis by "safety" capacitors of its time - something like 1n-5n/1kV.

[@Donno308]

Hi Kristof Well, it has turned out to be a stylish and apparently quite collectable little radio. That oscillation is a bit of a mystery but I'm sure you will work it out. I wonder if your shorting tuning capacitor is in fact bad earthing of the rotor vanes. maybe attach a clip lead to the rotor to chassis & see if it changes? Anyway, another great job! Now you have a hundred or so other radios to fix! I wonder how much freight would be to Australia... Cheers

[@retro_tech]

Haha, thanks! Indeed, difficult to know where to start first.

[@andybbeck2043]

super job 👏

[@retro_tech]

Thanks!

[@geirendre]

Oscillation can come from positive feedback (or lack of negative feedback) in the amplifier. So check the 1K resistor and the 1uF capacitor between the speaker and volume control. It could probably also be something wrong with the output tube, so it starts oscillating when it gets hot enough.

[@retro_tech]

Thanks for the suggestions. I'm also suspecting the output tube. I'll post an update as soon as I acquired a replacement tube.

[@PatrikS57AP]

Hiw did you clen The tuning capacitor at the end? I would need some advice myself. Great video!

[@retro_tech]

I didn't manage to get all the corrosion off. I cleaned it as much as I could with fine sandpaper and no-residue contact spray for highly sensitive equipment. In the end I gave up and accepted the fact that there are still a some shorts in there.