ВЭФ 12 (Astrad VEF 12 Project) - including a transistor tutorial

[Cardigan]

If the metal case of a transistor is not grounded it can basically act like an aerial when you touch it, thus giving all sorts of whistles from pick up. You get this effect on AF117's if the screen is cut off.

I've had the issue where cutting the screen lead restores life, but with instability. I have never tried reconnecting the screen back to its 'earthy' connection via a small capacitor - I suspect that will kill any signals but I wonder if anyone has tried it?