Heath DX-40: two different modulator circuits?

Discussion in '"Boat Anchor" & Classic Equipment' started by K5DH, Aug 11, 2018 at 1:48 AM.

ad: L-HROutlet
ad: l-rl
ad: MessiPaoloni-1
ad: l-BCInc
ad: Left-2
ad: L-MFJ
ad: l-assoc
ad: Subscribe
ad: Left-3
  1. K5DH

    K5DH Ham Member QRZ Page

    Okay, DX-40 mavens, let's see if you can help me. I've seen photos of the underside of various DX-40 chassis and it looks like there were two different circuits, mainly in the modulator section. I'm fixing up a DX-40 whose modulator section differs quite a bit from the schematic that I have, but the circuitry looks just like a bunch of the photos I've seen on line. I recall seeing a reference to there being two different circuits, but I can't find it. Can someone shed some light here? If there are two different circuits, which one is better and why?
     
  2. N2EY

    N2EY Ham Member QRZ Page

    I'm no DX-40 maven, nor an expert in anything.....but I'd like to help if I can.

    Can you show us some photos and trace out the as-wired circuits?

    ----

    The DX-40 uses a form of controlled-carrier screen modulation. The basic circuit operation is explained in the manual. It's possible that some folks didn't like the controlled-carrier system and changed it to straight screen modulation, despite the fact that controlled carrier gives more power output.

    73 de Jim, N2EY
     
    Last edited: Aug 12, 2018 at 8:49 PM
  3. K9STH

    K9STH Ham Member Volunteer Moderator QRZ Page

    There was a change made by Heath with the modulator in the DX-40 sometime in the production run. However, I have no documentation as to just what was changed and exactly when the change was made.

    There has been some information on this posted on one of the boat anchor E-Mail reflectors quite a ways back. But, I just do not know on which reflector the information appeared.

    The only thing that I remember was that certain component values were changed to increase the audio power and to improve the frequency response.

    Glen, K9STH
     
  4. AC0OB

    AC0OB Subscriber QRZ Page

    These are the latest upgrades I use for a DX-40:


    Pheel
     

    Attached Files:

Share This Page