[Heath] DX-40

[Wilson Lamb]

V4a feeds the grid of V4b.  The important thing is that V4b is a cathode follower, with its output taken from the cathode.  The plate is basically grounded (for AC) through the subject capacitor, to make the audio appear at the cathode.  The .02 cap is probably enough and more doesn't matter much, although it might raise the bass response some.
WL
  ----- Original Message ----- 
  From: G3OOU at aol.com 
  To: TDavid at industrialcoating.com ; heath at puck.nether.net 
  Sent: Monday, April 25, 2011 5:59 PM
  Subject: Re: [Heath] DX-40


  In a message dated 25/04/2011 19:47:11 GMT Standard Time, TDavid at industrialcoating.com writes:
    A DX-40 question – the DX-40 I recently acquired has a 20uF cap from pin 1 of the 6DE7 to the chassis.   The schematic in the partial manual I have doesn’t show the cap.  On  the chassis side it is tied to a solder lug so it appears that some thought was given to installing it.  Can someone with a later diagram confirm if it is correctly installed or, if not, where it should be connected?    

    Thanks for the help! 

    Dave Cohen, N7TC

  Hi Dave

  My DX40 schematic shows an 0.02uF capacitor from pin 1 of V4 to ground but no date or version number on the sheet. Your 20uF capacitor might be an attempt at additional decoupling in conjunction with R21 (1K). The DC is shown as +380V at pin 1 of V4 and this will contain an audio component during modulation.

  73

  Bob
  Bob F Burns
  C Eng, FIET, MSE
  Amateur Radio Callsign: G3OOU
  Registered RSGB Instructor
  G-QRP Member No: 6907; Zone: 14, QRA: IO91WH; WAB: TQ25
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