XPost: sci.electronics.design   
   From: JL@gct.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.   
   >https://disk.yandex.com/i/eKAe95xMsiIvNA   
   >   
   >I'm out of ideas. What could cause such distortion if the PS rail isn't   
   >responsible?   
   >   
   >Your pal,   
   >   
   >CD.   
   >   
      
   Maybe the light bulb broke.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)