XPost: sci.electronics.design   
   From: cd999666@notformail.com   
      
   On Sun, 13 Oct 2024 17:10:30 -0000 (UTC), Cursitor Doom wrote:   
      
   > Gentlemen,   
   >   
   > Last week I got an old (1968) pulse generator out of mothballs and   
   > managed to get it fully functional again. However, before replacing the   
   > case, I (true to form) dropped it on the bench and something on the PCB   
   > must have shorted out against the metal tools it fell on, because it no   
   > longer works properly.   
   > I've found an issue with the principal oscillator. It's generating   
   > distorted sine waves. It's a wien bridge type using BJTs as the gain   
   > element and fine tungsten filaments as thermistors, so should produce   
   > near perfect sine waves before they're chopped and shaped by subsequent   
   > circuitry, but since the fall, it's not.   
   >   
   > Here's the oscillator output:   
   > https://disk.yandex.com/i/eKAe95xMsiIvNA   
   >   
   > I found some weird periodic spikes on the power supply rails in the   
   > oscillator stage. They are actually present on the rail, not just picked   
   > up by the ground lead of the scope out of the ether, as I used a short   
   > ground clip in this instance. I'm not sure if these could cause the   
   > distortion or not.   
   > [removed]   
   >   
   > I'm out of ideas. What could cause such distortion if the PS rail isn't   
   > responsible?   
   >   
   > Your pal,   
   >   
   > CD.   
      
   Sorry, the trace of the 'ripple' should have been this link:   
   https://disk.yandex.com/i/P7AIraCaJybIMw   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)